Are risk factors the same for small for gestational age versus other preterm births?

Should we use composite outcomes in obstetric clinical prediction models?

Clinical prediction models assist clinicians to estimate the natural course of a condition, and thus facilitate treatment decisions. The development of prediction models is increasingly common in obstetric research. Composite outcomes, whereby multiple outcomes are combined into a single endpoint, are frequently used in obstetric prediction models to increase statistical power when predicting rare events. Although existing literature has reviewed the positives and negatives of using composite outcomes in clinical trials, there has been minimal commentary on the implications of their use in the development and reporting of prognostic models. In this article, we review these issues, in particular, highlighting how unequal individual relationships between predictors and individual component outcomes can result in misleading conclusions, which may result in the omission of important but rare predictors or inappropriately inform clinical decisions to implement an intervention. We propose careful use, or where possible avoidance, of composite outcomes in the development of prognostic models in obstetrics. Methodological standards for developing prognostic models should be updated to standardise and appraise composite outcomes when their use is necessary. We also support previous recommendations to report on the accuracy of key components and inconsistencies among predictor variables.

The Effect of Maternal Race, Ethnicity, and Nativity on Macrosomia Among Infants Born in the United States

OBJECTIVES

 This study aims to elucidate the influence of race, ethnicity, and nativity on macrosomia rates, hypothesizing that higher rates are observed among White non-Latina mothers and United States (US)-born mothers.

STUDY DESIGN

 We analyzed data from 1,791,718 US births sourced from the National Center for Health Statistics of the Centers for Disease Control and Prevention. Logistic regression analyses were conducted to examine the associations between macrosomia rates and maternal race, ethnicity, and nativity.

RESULTS

 After excluding non-singleton, preterm, post-term births, and those with missing data, six maternal cohorts were identified: White non-Latina US-born (1,147,096) and foreign-born (75,542), Black non-Latina US-born (174,540) and foreign-born (32,200), and Latina US-born (223,968) and foreign-born (137,515). White non-Latina US-born mothers had the highest rates of excessive gestational weight gain (58.9%). Black non-Latina US-born mothers exhibited the highest rates of pre-pregnancy diabetes (0.7%) and obesity (29.5%). Macrosomia rates were highest among White non-Latina US-born mothers (10.7%) compared to other cohorts. After adjusting for socioeconomic and health-related factors, this group maintained the highest odds of macrosomia (OR: 1.876; 95%CI 1.832-1.922, P<0.001).

CONCLUSION

Our findings reveal that White non-Latina US-born mothers experience the highest macrosomia rates, which persist after adjusting for known confounders. These results have significant implications for the development of gestational surveillance tools and targeted public health interventions aimed at improving pregnancy outcomes among high-risk cohorts.

The effects of maternal hypertension on the early neonatal platelet count

OBJECTIVE

To examine the relationship between maternal hypertension and early neonatal platelet counts.

STUDY DESIGN

This single site retrospective cohort study compared initial platelet counts in the first day of life of infants born to mothers with preeclampsia with severe features (PSF) (n = 224) and infants born to normotensive mothers using multivariable logistic and Quasi-Poisson regression models.

RESULT

There was no statistical difference in initial platelet counts or likelihood of thrombocytopenia (aOR = 1.19, 95% CI 0.68-2.08) between infants born to mothers with PSF and infants born to normotensive mothers after multivariable adjustment. Initial platelet counts and thrombocytopenia risk were unaffected by the presence of maternal end organ dysfunction. Small for gestational age (SGA) status was the most significant risk factor for the development of thrombocytopenia (aOR = 2.24, 95% CI 1.13-4.30).

CONCLUSION

Maternal PSF does not directly affect neonatal initial platelet counts. SGA status confers the greatest risk of early thrombocytopenia.

Hurricane Michael and Adverse Birth Outcomes in the Florida Panhandle: Analysis of Vital Statistics Data

OBJECTIVE

The aim of this study was to examine birth outcomes in areas affected by Hurricane Michael.

METHODS

Vital statistics data of 2017-2019 were obtained from the state of Florida. Births occurring in the year before and after the date of Hurricane Michael (October 7, 2018) were used. Florida counties were divided into 3 categories reflecting extent of impact from Hurricane Michael. Birth outcomes including incidence of preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA) were also compared before and after Hurricane Michael. Spontaneous and indicated PTBs were distinguished based on previously published algorithms. Multiple regression was used to control for potential confounders.

RESULTS

Both LBW (aRR 1.19, 95% CI: 1.07, 1.32) and SGA (aRR 1.11, 95% CI: 1.01, 1.21) were higher in the year after Michael than the year before in the most-affected area; a similar effect was not seen in other areas. A stronger effect was seen for exposure in the first trimester or in the 2 months after Michael than in the second or third trimester.

CONCLUSION

Consistent with many previous studies, this study of Hurricane Michael found an effect on fetal growth.

Preconception and early-pregnancy risk prediction for birth complications: development of prediction models within a population-based prospective cohort

Background

Suboptimal maternal health already from preconception onwards is strongly linked to an increased risk of birth complications. To enable identification of women at risk of birth complications, we aimed to develop a prediction model for birth complications using maternal preconception socio-demographic, lifestyle, medical history and early-pregnancy clinical characteristics in a general population.

Methods

In a population-based prospective cohort study among 8340 women, we obtained information on 33 maternal characteristics at study enrolment in early-pregnancy. These characteristics covered the preconception period and first half of pregnancy (< 21 weeks gestation). Preterm birth was < 37 weeks gestation. Small-for-gestational-age (SGA) and large-for-gestational-age (LGA) at birth were gestational-age-adjusted birthweight in the lowest or highest decile, respectively. Because of their co-occurrence, preterm birth and SGA were combined into a composite outcome.

Results

The basic preconception model included easy obtainable maternal characteristics in the preconception period including age, ethnicity, parity, body mass index and smoking. This basic preconception model had an area under the receiver operating characteristics curve (AUC) of 0.63 (95% confidence interval (CI) 0.61 to 0.65) and 0.64 (95% CI 0.62 to 0.66) for preterm birth/SGA and LGA, respectively. Further extension to more complex models by adding maternal socio-demographic, lifestyle, medical history and early-pregnancy clinical characteristics led to small, statistically significant improved models. The full model for prediction of preterm birth/SGA had an AUC 0.66 (95% CI 0.64 to 0.67) with a sensitivity of 22% at a 90% specificity. The full model for prediction of LGA had an AUC of 0.67 (95% CI 0.65 to 0.69) with sensitivity of 28% at a 90% specificity. The developed models had a reasonable level of calibration within highly different socio-economic subsets of our population and predictive performance for various secondary maternal, delivery and neonatal complications was better than for primary outcomes.

Conclusions

Prediction of birth complications is limited when using maternal preconception and early-pregnancy characteristics, which can easily be obtained in clinical practice. Further improvement of the developed models and subsequent external validation is needed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04497-2.

Maternal Serum Antioxidants in Mid Pregnancy and Risk of Preterm Delivery and Small for Gestational Age Birth: Results from a Prospective Pregnancy Cohort

Background: Preterm delivery (PTD) and poor fetal growth are major contributors to neonatal mortality and morbidity that can extend from birth onward. Although overt maternal nutrient deficiencies are associated with adverse pregnancy outcomes, such deficiencies are rare in developed countries. However, some evidence suggests that even within the normal range, higher levels of antioxidant nutrients are protective against adverse pregnancy outcomes. Materials and Methods: Using data from the prospective Pregnancy Outcomes and Community Health (POUCH) Study (n = 301 preterm; n = 246 term), we examined associations between maternal blood levels of selected antioxidants and pregnancy outcomes. Serum collected at 16-27 weeks' gestation was analyzed for carotenoids, retinol, and α- and γ-tocopherol. Using weighted polytomous regression, these nutrient concentrations were assessed in relation to (1) PTD (<37 weeks gestation) overall and grouped as spontaneous or medically indicated; and (2) small for gestational age (SGA) defined as birthweight-for-gestational age <10th percentile of a national reference population. Results: Women with total serum carotenoids in the upper quartile (Q4) had significantly lower odds of medically indicated PTD compared with women in the lower quartiles (Q1-Q3) even after adjustment for maternal characteristics (aOR = 0.4; 95% CI: 0.2-0.9). Odds ratios for SGA were consistently ≤0.5 among women with any of the serum nutrients in Q4 as compared with Q1-Q3, but final models did not reach statistical significance. Conclusion: Results support the possibility that high maternal serum antioxidants and/or the larger dietary or lifestyle pattern they represent may play a protective role in preventing adverse pregnancy outcomes.

Clinical Outcomes in High-Risk Pregnancies Due to Advanced Maternal Age

Although the influence of advanced maternal age (AMA) and delayed childbearing on adverse maternal and perinatal outcomes has been studied extensively, no universal consensus on the definition of AMA exists. This terminology currently refers to the later years of a woman's reproductive life span and generally applies to women age ≥35 years. AMA increases the risk of pregnancy complications, including ectopic pregnancy, spontaneous abortion, fetal chromosomal abnormalities, congenital anomalies, placenta previa and abruption, gestational diabetes, preeclampsia, and cesarean delivery. Such complications could be the cause of preterm birth and increase the risk of perinatal mortality. For women who have a chronic illness, pregnancy may lead to additional risk that demands increased monitoring or surveillance. The management of pregnant women of AMA requires understanding the relationship between age and preexisting comorbidities. The outcomes from pregnancy in AMA may have a negative impact on women's health as they age because of both the changes from the pregnancy itself and the increased risk of pregnancy-related complications. Postpartum depression affects women of AMA at higher rates. Links between preeclampsia and the risk of future development of cardiovascular disease require follow-up surveillance. The association between hypertensive pregnancy disorders and cognitive and brain functions needs further investigation of sex-specific risk factors across the life span. Educating providers and women of AMA is crucial to facilitate clinical decision making and such education should consider cultural influences, risk perception, and women's health literacy, as well as providers' biases and system issues.

Cytokine profiles in maternal serum are candidates for predicting an optimal timing for the delivery in early-onset fetal growth restriction

OBJECTIVE

We examined whether maternal serum cytokine profiles of mothers with early-onset fetal growth restriction (FGR) were associated with delivery within 2 weeks after sampling during the third trimester.

STUDY DESIGN

This exploratory prospective cross-sectional study included a total of 20 singleton fetuses with early-onset FGR and 31 healthy controls. Maternal serum samples during the early third trimester were analyzed for 23 cytokines.

RESULTS

Of 20 fetuses with early-onset FGR, 14 had delivery within 2 weeks after sampling. Multivariate analysis revealed that maternal serum concentrations of soluble vascular endothelial growth factor receptor-1 (sVEGFR-1) and soluble CD40 ligand (sCD40L) were independently associated with delivery within 2 weeks in early-onset FGR. Among cases of early-onset FGR, concentrations of almost all maternal serum cytokines were similar. Maternal serum sVEGFR-1 concentrations were high when delivery occurred within 2 weeks. Maternal serum sCD40L concentrations were elicited only in cases in which delivery within 2 weeks occurred due to fetal deterioration.

CONCLUSION

We identified two biomarkers, one specific for FGR and the other dependent on severity, that were significant components of angiogenic activities and inflammation factors. Imbalances in serum protein expression may have a substantial effect on the pathogenesis of FGR.

Neighbourhood Income and Risk of Having an Infant With Concomitant Preterm Birth and Severe Small for Gestational Age Birth Weight

OBJECTIVE

Socioeconomic position gradients have been individually demonstrated for preterm birth (PTB) at <37 weeks gestation and severe small for gestational age birth weight at <5th percentile (SGA). It is not known how neighbourhood income is related to the combination of PTB and severe SGA, a state reflective of greater placental dysfunction and higher risk of neonatal morbidity and mortality than PTB or severe SGA alone.

METHODS

This population-based study comprised all 1 367 656 singleton live births in Ontario from 2002 to 2011. Multinomial logistic regression was used to estimate the odds of PTB with severe SGA, PTB without severe SGA, and severe SGA without PTB, compared with neither PTB nor severe SGA, in relation to neighbourhood income quintile (Q). The highest income quintile, Q5, served as the exposure referent. Adjusted odds ratios (aORs) were adjusted for maternal age at delivery, parity, marital status, and world region of birth (Canadian Task Force Classification II-2).

RESULTS

Relative to women residing in Q5 (2.3 per 1000), the rate of PTB with severe SGA was highest among those in Q1 (3.6 per 1000), with an aOR of 1.34 (95% confidence interval [CI] 1.20-1.50). The corresponding aORs were 1.23 (95% CI 1.09-1.37) for Q2, 1.14 (95% CI 1.02-1.28) for Q3, and 1.06 (95% CI 0.95-1.20) for Q4. Less pronounced aORs were seen for each individual outcome of PTB and severe SGA.

CONCLUSION

Women residing in the lowest-income areas are at highest risk of having a fetus born too small and too soon. Future research should focus on identifying those women most predisposed to combined PTB and severe SGA.

The prevalence and risk factors of preterm small-for-gestational-age infants: a population-based retrospective cohort study in rural Chinese population

Background

Preterm birth and small for gestational age (SGA) are strong indicators of neonatal adverse outcomes. With the growing importance of preterm SGA infants, we aim to evaluate the prevalence and risk factors for preterm SGA in China.

Method

We analyzed the data of parents and infants from a population-based cohort research of the free National Pre-pregnancy Checkups Project (NPCP) in rural China. Only singleton live births that occurred between 24 weeks +0 days and 36 weeks +6 days of pregnancy were included in this study. SGA was defined as birth weight less than the 10th percentile of the reference birth-weight-for-gestational-age population. A multiple logistic regression model was built using the statistically significant variables from the 371 variables in the questionnaire.

Results

A total of 11,474 singleton, preterm, live-birth infants were included. Of the total infants, 317 (2.77%) were preterm SGA infants. A higher risk of preterm SGA infants was observed among mothers who were on oral contraceptives (OR: 8.162, 95% CI: 1.622–41.072), mothers who had syphilis (OR: 12.800, 95% CI: 1.250–131.041), and mothers with a high eosinophil percentage (OR: 13.292, 95% CI: 1.282–135.796). Maternal intake of folic acid at least 3 months before pregnancy (OR: 0.284, 95% CI:0.124–0.654) and paternal intake of egg and meat (OR: 0.097,95% CI:0.030–0.315) were protective factors. Compared with North China, the incidence of preterm SGA infants was higher in South China.

Conclusion

Preterm SGA infants were associated with both maternal and paternal factors.

Risk factors for low birth weight and preterm birth: A population-based case-control study in Wuhan, China

Low birth weight (LBW) and preterm birth (PB) are associated with newborn mortality and diseases in adulthood. We explored factors related to LBW and PB by conducting a population-based case-control study from January 2011 to December 2013 in Wuhan, China. A total of 337 LBW newborn babies, 472 PB babies, and 708 babies with normal birth weights and born from term pregnancies were included in this study. Information of newborns and their parents was collected by trained investigators using questionnaires and referring to medical records. Univariate and logistic regression analyses with the stepwise selection method were used to determine the associations of related factors with LBW and PB. Results showed that maternal hypertension (OR=6.78, 95% CI: 2.27-20.29, P=0.001), maternal high-risk pregnancy (OR=1.53, 95% CI: 1.06-2.21, P=0.022), and maternal fruit intake ≥300 g per day during the first trimester (OR=1.70, 95% CI: 1.17-2.45, P=0.005) were associated with LBW. BMI ≥24 kg/m² of mother prior to delivery (OR=0.48, 95% CI: 0.32-0.74, P=0.001) and gestation ≥37 weeks (OR=0.01, 95% CI: 0.00-0.02, P<0.034) were protective factors for LBW. Maternal hypertension (OR=3.36, 95% CI: 1.26-8.98, P=0.016), maternal high-risk pregnancy (OR=4.38, 95% CI: 3.26-5.88, P<0.001), maternal meal intake of only twice per day (OR=1.88, 95% CI: 1.10-3.20, P=0.021), and mother liking food with lots of aginomoto and salt (OR=1.60, 95% CI: 1.02-2.51, P=0.040) were risk factors for PB. BMI ≥24 kg/m² of mother prior to delivery (OR=0.66, 95% CI: 0.47-0.93, P=0.018), distance of house from road ≥36 meters (OR=0.72, 95% CI: 0.53-0.97, P=0.028), and living in rural area (OR= 0.60, 95% CI: 0.37-0.99, P=0.047) were protective factors for PB. Our study demonstrated some risk factors and protective factors for LBW and PB, and provided valuable information for the prevention of the conditions among newborns.

SOCIOECONOMIC STATUS AND ADVERSE BIRTH OUTCOMES: A POPULATION-BASED CANADIAN SAMPLE

This study assessed the strength of the association between socioeconomic status (SES) and low birth weight (LBW) and preterm birth (PTB) in Southwestern Ontario. Utilizing perinatal and neonatal databases at the London Health Science Centre, maternal postal codes were entered into a Geographic Information System to determine home neighbourhoods. Neighbourhoods were defined by dissemination areas (DAs). Median household income for each DA was extracted from the latest Canadian Census and linked to each mother. All singleton infants born between February 2009 and February 2014 were included. Of 26,654 live singleton births, 6.4% were LBW and 9.7% were PTB. Top risk factors for LBW were: maternal amphetamine use, chronic hypertension and maternal marijuana use (OR respectively: 17.51, 3.18, 2.72); previously diagnosed diabetes, maternal narcotic use and insulin-controlled gestational diabetes predicted PTB (OR respectively: 17.95, 2.69, 2.42). Overall, SES had little impact on adverse birth outcomes, although low maternal education increased the likelihood of a LBW neonate (OR: 1.01).

Life-course Social Mobility and Reduced Risk of Adverse Birth Outcomes

INTRODUCTION

Higher adult socioeconomic position (SEP) is associated with better birth outcomes. However, few studies incorporate life-course or intergenerational SEP, which may inform etiology and targeted prevention efforts. This study tested whether life-course social mobility from childhood was associated with lower risk of adverse birth outcomes.

METHODS

Data were from the Life-course Influences of Fetal Environments (LIFE) retrospective cohort study among black women, 2009-2011, in metropolitan Detroit, MI. This study (analyzed in 2014-2016) examined whether social mobility was associated with two primary birth outcomes: small for gestational age (SGA) and preterm birth (PTB). Childhood and adulthood SEP were measured by survey in adulthood, for two constructs, measured ordinally: educational attainment and perceived financial sufficiency (subjective income/wealth). Social mobility was calculated as the difference of adulthood minus childhood SEP.

RESULTS

In covariate-adjusted Poisson regression models, 1-SD improved educational social mobility from childhood to adulthood was protective for SGA (adjusted risk ratio=0.76; 95% CI=0.64, 0.91); this association remained after adjusting for financial mobility. Upward financial social mobility from early childhood was marginally protective for SGA (adjusted risk ratio=0.85; 95% CI=0.72, 1.02), but became nonsignificant after controlling educational mobility. There were no overall associations of social mobility with PTB or low birth weight, although sensitivity analyses identified that improved financial mobility was associated with 16% marginally lower risk of spontaneous PTB and 28% marginally lower risk of low birth weight among upwardly mobile/stable women only.

CONCLUSIONS

Improved life-course social mobility is associated with reduced risk for SGA and spontaneous PTB among black women.

Maternal Prepregnancy Body Mass Index and Small for Gestational Age Births in Chinese Women

BACKGROUND

Both high and low prepregnancy body mass index (BMI) has been associated with small for gestational age births (SGA; birthweight below the population specific 10th centile for the gestational age), but results remain inconsistent. We examined the association between maternal BMI and SGA, and evaluated if the associations were modified by preterm birth (being born prior to 37 weeks) status.

METHODS

A population-based cohort study was conducted in Wuhan, China from June 2011, to June 2013. Women who delivered a non-malformed livebirth (n = 76 695) were included using the Wuhan Maternal and Child Health Management Information System. Log-binomial regression models were used to analyse the associations between prepregnancy BMI, categorized using thresholds adapted to the Chinese population, and SGA. Stratified analyses were used to examine the relationship of prepregnancy BMI to preterm-SGA and term-SGA.

RESULTS

Of the 76 695 live births, 3058 (4.0%) were delivered preterm. For babies born at term, prepregnancy underweight (<18.5 kg/m² ) was associated with an increased risk of SGA, the adjusted risk ratio (RR) was 1.41 (95% confidence interval (CI) 1.33, 1.49), whereas, being overweight (24.0-27.9 kg/m² ) was associated with a decreased risk (RR 0.84, 95% CI 0.74, 0.94). For babies born preterm, prepregnancy underweight was not associated with risk of SGA, but being overweight was associated with an increased risk (RR 1.57, 95% CI 1.04, 2.35).

CONCLUSIONS

These data suggest that the association of overweight and underweight prepregnancy BMI and SGA differs depending on whether the baby is full term or preterm.

Preterm birth and fetal growth restriction in HIV-infected Brazilian pregnant women

Introduction:

Maternal HIV infection and related co-morbidities may have two outstanding consequences to fetal health: mother-to-child transmission (MTCT) and adverse perinatal outcomes. After Brazilian success in reducing MTCT, the attention must now be diverted to the potentially increased risk for preterm birth (PTB) and intrauterine fetal growth restriction (IUGR).

Objective:

To determine the prevalence of PTB and IUGR in low income, antiretroviral users, publicly assisted, HIV-infected women and to verify its relation to the HIV infection stage.

Patients and Methods:

Out of 250 deliveries from HIV-infected mothers that delivered at a tertiary public university hospital in the city of Vitória, state of Espírito Santo, Southeastern Brazil, from November 2001 to May 2012, 74 single pregnancies were selected for study, with ultrasound validated gestational age (GA) and data on birth dimensions: fetal weight (FW), birth length (BL), head and abdominal circumferences (HC, AC). The data were extracted from clinical and pathological records, and the outcomes summarized as proportions of preterm birth (PTB, < 37 weeks), low birth weight (LBW, < 2500g) and small (SGA), adequate (AGA) and large (LGA) for GA, defined as having a value below, between or beyond the ±1.28 z/GA score, the usual clinical cut-off to demarcate the 10th and 90th percentiles.

Results:

PTB was observed in 17.5%, LBW in 20.2% and SGA FW, BL, HC and AC in 16.2%, 19.1%, 13.8%, and 17.4% respectively. The proportions in HIV-only and AIDS cases were: PTB: 5.9 versus 27.5%, LBW: 14.7% versus 25.0%, SGA BW: 17.6% versus 15.0%, BL: 6.0% versus 30.0%, HC: 9.0% versus 17.9%, and AC: 13.3% versus 21.2%; only SGA BL attained a significant difference. Out of 15 cases of LBW, eight (53.3%) were preterm only, four (26.7%) were SGA only, and three (20.0%) were both PTB and SGA cases. A concomitant presence of, at least, two SGA dimensions in the same fetus was frequent.

Conclusions:

The proportions of preterm birth and low birth weight were higher than the local and Brazilian prevalence and a trend was observed for higher proportions of SGA fetal dimensions than the expected population distribution in this small casuistry of newborn from the HIV-infected, low income, antiretroviral users, and publicly assisted pregnant women. A trend for higher prevalence of PTB, LBW and SGA fetal dimensions was also observed in infants born to mothers with AIDS compared to HIV-infected mothers without AIDS.

Maternal caffeine consumption and small for gestational age births: results from a population-based case-control study

Caffeine is consumed in various forms during pregnancy, has increased half-life during pregnancy and crosses the placental barrier. Small for gestational age (SGA) is an important perinatal outcome and has been associated with long term complications. We examined the association between maternal caffeine intake and SGA using National Birth Defects Prevention Study data. Non-malformed live born infants with an estimated date of delivery from 1997-2007 (n = 7,943) were included in this analysis. Maternal caffeine exposure was examined as total caffeine intake and individual caffeinated beverage type (coffee, tea, and soda); sex-, race/ethnic-, and parity-specific growth curves were constructed to estimate SGA births. Crude and adjusted odds ratios (aORs) and 95% confidence intervals were estimated using unconditional logistic regression. Interaction with caffeine exposures was assessed for maternal smoking, vasoconstrictor medication use, and folic acid. Six hundred forty-eight infants (8.2%) were found to be SGA in this analysis. Increasing aORs were observed for increasing intakes of total caffeine and for each caffeinated beverage with aORs (adjusting for maternal education, high blood pressure, and smoking) ranging from 1.3 to 2.1 for the highest intake categories (300+ mg/day total caffeine and 3+ servings/day for each beverage type). Little indication of additive interaction by maternal smoking, vasoconstrictor medication use, or folic acid intake was observed. We observed an increase in SGA births for mothers with higher caffeine intake, particularly for those consuming 300+ mg of caffeine per day. Increased aORs were also observed for tea intake but were more attenuated for coffee and soda intake.

Risk factors and adverse perinatal outcomes among term and preterm infants born small-for-gestational-age: secondary analyses of the WHO Multi-Country Survey on Maternal and Newborn Health

BACKGROUND

Small for gestational age (SGA) is not only a major indicator of perinatal mortality and morbidity, but also the morbidity risks in later in life. We aim to estimate the association between the birth of SGA infants and the risk factors and adverse perinatal outcomes among twenty-nine countries in Africa, Latin America, the Middle East and Asia in 359 health facilities in 2010-11.

METHODS

We analysed facility-based, cross-sectional data from the WHO Multi-country Survey on Maternal and Newborn Health. We constructed multilevel logistic regression models with random effects for facilities and countries to estimate the risk factors for SGA infants using country-specific birthweight reference standards in preterm and term delivery, and SGA's association with adverse perinatal outcomes. We compared the risks and adverse perinatal outcomes with appropriate for gestational age (AGA) infants categorized by preterm and term delivery.

RESULTS

A total of 295,829 singleton infants delivered were analysed. The overall prevalence of SGA was highest in Cambodia (18.8%), Nepal (17.9%), the Occupied Palestinian Territory (16.1%), and Japan (16.0%), while the lowest was observed in Afghanistan (4.8%), Uganda (6.6%) and Thailand (9.7%). The risk of preterm SGA infants was significantly higher among nulliparous mothers and mothers with chronic hypertension and preeclampsia/eclampsia (aOR: 2.89; 95% CI: 2.55-3.28) compared with AGA infants. Higher risks of term SGA were observed among sociodemographic factors and women with preeclampsia/eclampsia, anaemia and other medical conditions. Multiparity (> = 3) (AOR: 0.88; 95% CI: 0.83-0.92) was a protective factor for term SGA. The risk of perinatal mortality was significantly higher in preterm SGA deliveries in low to high HDI countries.

CONCLUSION

Preterm SGA is associated with medical conditions related to preeclampsia, but not with sociodemographic status. Term SGA is associated with sociodemographic status and various medical conditions.

Associations of maternal asthma severity and control with pregnancy complications

OBJECTIVES

To assess the associations of maternal asthma severity and control with pregnancy-induced hypertension (PIH), gestational diabetes and cesarean delivery.

METHODS

A cohort of 41 660 pregnancies from women with and without asthma who delivered between 1990 and 2002 was constructed by linking Québec's administrative databases. Maternal asthma was defined by at least one asthma diagnosis and one dispensed prescription for an asthma medication in the 2 years before or during pregnancy. Asthma severity and control were assessed using validated indexes during the entire pregnancy to study cesarean delivery and 1-year prior to week 20 of gestation to study PIH and gestational diabetes. Generalized Estimation Equation models were used to obtain odds ratios (OR) for PIH, gestational diabetes and cesarean in association with maternal asthma severity and control.

RESULTS

Almost one-third of the women had uncontrolled asthma and up to 5% had severe asthma. Severe asthma increased the risk of cesarean delivery (OR = 1.35; 95% CI: 1.11-1.63) compared with mild asthma, but no association was found between asthma severity and the other outcomes. The level of asthma control was not associated with any of the outcomes, except for a near-significant increased risk of PIH among uncontrolled women (OR = 1.18; 95% CI: 0.97-1.42).

CONCLUSIONS

The risk of gestational diabetes was not associated with asthma severity or control, and the risk of PIH was not associated with asthma severity. However, further studies are needed to clarify the association between asthma control and PIH. The increased risk of cesarean among women with severe asthma may be explained by the physician's and patient's concerns over the safety of normal delivery.

Prevalence and risk factors associated with preterm birth in Ardabil, Iran

BACKGROUND

Preterm birth is a leading cause of perinatal mortality and long-term morbidity as well as the long-term health consequences and cognitive outcomes.

OBJECTIVE

Present study was conducted to determine prevalence and risk factors associated with preterm birth in Ardabil, Iran.

MATERIALS AND METHODS

A case control study was conducted between Nov 2010 and July 2011 in all three maternal hospitals in Ardabil. All the live newborns during the study period were investigated. Of 6705 live births during the study period 346 births occurred in <37 weeks were taken as a case and 589 term neonates were taken as a control group. Data were obtained through review of prenatal and hospital delivery records. Univariate and multivariate logistic regression analysis were applied to obtain magnitude of association between independent variables and preterm birth.

RESULTS

The prevalence rate of preterm birth was 5.1%. History of previous preterm birth (OR=12.7,CI: 3.9-40.4, p<0.001), hypertension (OR=7.3, CI:2.1-25.4, p=0.002), Oligohydramnios (OR=3.9, CI:1.6-9.5, p=0.002), spouse abuse (OR=3.7, CI:1.1-11.8, p=0.024), preeclampsia (OR=3.6, CI:1.3-10.3, p=0.014), premature rupture of membrane (OR=3.1, CI:1.9-4.9, p=0.000), bleeding or spotting during pregnancy (OR=2.0, CI:1.0-3.8, p=0.037), Hyperemesis Gravid arum (OR=2.0, CI: 1.1-3.8, p=0.015), urinary tract infection in 26-30 weeks , (OR=1. 8 CI:1.0-3.2, p=0.04), diastolic blood pressure ≤60 mmg (OR=1.5, CI: 0.99-2.2, p=0.049) were determined as significant risk factors for preterm birth.

CONCLUSION

Early detection and treatment of diseases or disorders among pregnant women especially hypertension, Oligohydramnios, preeclampsia, bleeding or spotting, Hyperemesis Gravid arum, urinary tract infection, and low diastolic blood pressure as well as the improving health care quality delivered to pregnant women may reduce preterm prevalence rate.

Contribution of socioeconomic status to the risk of small for gestational age infants--a population-based study of 1,390,165 singleton live births in Finland

Background

Small for gestational age (SGA) infants are at increased risk of short- and long-term adverse outcomes.

Methods

Population-based case–control study using data derived from the Finnish Medical Birth Register for the years 1987–2010 (total population of singleton live births n = 1,390,165). The aim was to quantify the importance of risk factors for SGA and describe their contribution to socioeconomic status (SES) disparities in SGA by using logistic regression analysis.

Results

Of all the singleton live births (n = 1,390,165), 3.1% (n = 42,702) were classified as SGA (defined as below 2 standard deviations of the sex-specific population reference mean for gestational age). The risk of SGA was 11 − 24% higher in the lower SES groups compared to the highest SES group. Smoking alone made the largest contribution, explaining 41.7 − 50.9% of SES disparities in SGA. The risk of SGA was 2.3-fold and 7% higher among women who smoked or had quit smoking during the first trimester of pregnancy (adjusted odds ratio (aOR) 2.34, 95% CI 2.28-2.42 and aOR 1.07, 95% CI 1.00 − 1.15, respectively) compared with the non-smokers.

Conclusions

SGA is substantially affected by SES. Smoking explained up to 50% of the difference in risk of SGA between high and low SES groups. Quitting smoking during the first trimester of pregnancy resulted in a 7% higher incidence of SGA comparable to that of non-smoking women. Thus, interventional attempts to reduce smoking during pregnancy might help to decrease the socioeconomic gradient of SGA.

Low birth weight in newborns to women employed in jobs with frequent exposure to organic solvents

The effects of occupational exposure to organic solvents in pregnancy on foetal growth are still unclear. Our aim was to study whether live newborns to women employed in paid jobs with frequent exposure had a different risk of being born with low birth weight (LBW), compared to those of women in jobs without such exposure. The study population was all singleton newborns delivered in the industrial township of Mončegorsk (N = 26,415). Information about occupation and characteristics of the mothers and babies was obtained from the local population-based birth register, and registered job function was used to classify exposure. We observed an elevated risk of LBW among live, singleton newborns in the exposed group (adjusted odds ratio: 1.68 [95% CI: 1.18-2.41]), which predominantly consisted of painters. The adjusted odds of LBW in the exposed group were also higher among term-born neonates. In addition, a lower mean birth weight was observed among the exposed.

Risk factors for preterm birth and small-for-gestational-age births among Canadian women

BACKGROUND

Preterm births (PTB) and small-for-gestational-age (SGA) births are distinct but related pregnancy outcomes, with differing aetiologies and short and long-term morbidities. Few studies have compared a broad array of predictors among these two outcomes. The purpose of this study was to compare risk factors for PTB and SGA births using a national sample of Canadian women.

METHODS

We analysed data from the Canadian Maternity Experiences Survey (n = 6421). Mothers were ≥ 15 years of age, gave birth to a singleton infant and were living with their infant at the time of the interview (between 5 and 14 months post-partum). Backward stepwise multivariable logistic regression models were constructed for each outcome.

RESULTS

Risk profiles for the two outcomes had both differences and similarities. Risk factors specific to PTB were education less than high school, having a previous medical condition, developing a new medical condition or health problem during pregnancy, being a primigravida, or being a multigravida with a previous PTB or a previous miscarriage or abortion. Risk factors unique to SGA were low pre-pregnancy body mass index (<18 kg/m(2) ), smoking during pregnancy and being a recent immigrant. Risk factors for both outcomes included low weight gain during pregnancy (<9.1 kg), short stature (<155 cm) and reporting life as 'very stressful' in the year prior to birth of the baby.

CONCLUSION

A greater understanding of the risk factors related to PTB and SGA may help to reduce the prevalence of these conditions and the associated risk of infant mortality and morbidity.

Risks of small-for-gestational-age births in immigrants: A nationwide epidemiological study in Sweden

Aim: To examine if there is an association between country of birth in parents and small-for-gestational-age (defined as a birthweight of more than two standard deviations (SDs) below the mean) in first singletons births. Methods: In this follow-up study, national population and healthcare registers were used to identify small-for-gestational-age births in all first singleton births in Sweden between 1 January 1982 and 31 December 2006. Odds ratios, standardised with regard to maternal age at birth, period of birth, marital status, family income, geographical region, employment, maternal height, and smoking history, were estimated by maternal and paternal country of birth. Singletons with both parents born in Sweden were used as reference group. Results: There were 1,060,467 records for first singletons births over the study period, of whom 3.5% were small-for-gestational-age. The rate was higher in newborns with non-Swedish born than in those with Swedish born mothers (4.1 and 3.3%, respectively). Immigrants from Southern European countries, Africa, and Asia had higher risks of small-for-gestational-age in than those in the reference group, and the risks were even higher in compatriot parents. Conclusions: Country of birth affected the risk of small-for-gestational-age. Maternity care should pay a special attention to pregnancies in certain population groups.

Preeclampsia complicated by advanced maternal age: a registry-based study on primiparous women in Finland 1997-2008

Background

Preeclampsia is a frequent syndrome and its cause has been linked to multiple factors, making prevention of the syndrome a continuous challenge. One of the suggested risk factors for preeclampsia is advanced maternal age. In the Western countries, maternal age at first delivery has been steadily increasing, yet few studies have examined women of advanced maternal age with preeclampsia. The purpose of this registry-based study was to compare the obstetric outcomes in primiparous and preeclamptic women younger and older than 35 years.

Methods

The registry-based study used data from three Finnish health registries: Finnish Medical Birth Register, Finnish Hospital Discharge Register and Register of Congenital Malformations. The sample contained women under 35 years of age (N = 15,437) compared with those 35 and over (N = 2,387) who were diagnosed with preeclampsia and had their first singleton birth in Finland between 1997 and 2008. In multivariate modeling, the main outcome measures were Preterm delivery (before 34 and 37 weeks), low Apgar score (5 min.), small-for-gestational-age, fetal death, asphyxia, Cesarean delivery, induction, blood transfusion and admission to a Neonatal Intensive Care Unit.

Results

Women of advanced maternal age (AMA) exhibited more preeclampsia (9.4%) than younger women (6.4%). They had more prior terminations (<0.001), were more likely to have a body mass index (BMI) >25 (<0.001), had more in vitro fertilization (IVF) (<0.001) and other fertility treatments (<0.001) and a higher incidence of maternal diabetes (<0.001) and chronic hypertension (<0.001). Multivariate logistic regression indicated that women of AMA had higher rates of: preterm delivery before 37 weeks 19.2% (OR 1.39 CI 1.24 to 1.56) and before 34 weeks 8.7% (OR 1.68 CI 1.43 to 2.00) low Apgar scores at 5 min. 7.1% (OR 1.37 CI 1.00 to 1.88), Small-for-Gestational Age (SGA) 26.5% (OR 1.42 CI 1.28 to 1.57), Asphyxia 12.1% (OR 1.54 CI 1.34 to 1.77), Caesarean delivery 50% (OR 2.02 CI 1.84 to 2.20) and admission to a Neonatal Intensive Care Unit (NICU) 31.6% (OR 1.45 CI 1.32 to 1.60).

Conclusions

Preeclampsia is more common in women with advanced maternal age. Advanced maternal age is an independent risk factor for adverse outcomes in first-time mothers with preeclampsia.

Maternal HIV infection associated with small-for-gestational age infants but not preterm births: evidence from rural South Africa

BACKGROUND

 Human immunodeficiency virus (HIV) is prevalent in many countries where small-for-gestational age (SGA) and premature delivery are also common. However, the associations between maternal HIV, preterm delivery and SGA infants remain unclear. We estimate the prevalence of SGA and preterm (<37 weeks) births, their associations with antenatal maternal HIV infection and their contribution to infant mortality, in a high HIV prevalent, rural area in South Africa.

METHODS

Data were collected, in a non-randomized intervention cohort study, on all women attending antenatal clinics (2001–2004), before the availability of antiretroviral treatment. Newborns were weighed and gestational age was determined (based on last menstrual period plus midwife assessment antenatally). Poisson regression with robust variance assessed risk factors for preterm and SGA birth, while Cox regression assessed infant mortality and associated factors.

RESULTS

Of 2368 live born singletons, 16.6% were SGA and 21.4% were preterm. HIV-infected women (n= 1189) more commonly had SGA infants than uninfected women (18.1 versus 15.1%; P = 0.051), but percentages preterm were similar (21.8 versus 20.9%; P = 0.621). After adjustment for water source, delivery place, parity and maternal height, the SGA risk in HIV-infected women was higher [adjusted relative risk (aRR) 1.28, 95% confidence interval (CI): 1.06–1.53], but the association between maternal HIV infection and preterm delivery remained weak and not significant (aRR: 1.07, 95% CI: 0.91–1.26). In multivariable analyses, mortality under 1 year of age was significantly higher in SGA and severely SGA than in appropriate-for-gestational-age infants [adjusted hazard ratio (aHR): 2.12, 95% CI: 1.18–3.81 and 2.77, 95% CI: 1.56–4.91], but no difference in infant mortality was observed between the preterm and term infants (aHR: 1.18 95% CI: 0.79–1.79 for 34–36 weeks and 1.31, 95% CI: 0.58–2.94 for <34 weeks).

CONCLUSIONS

Maternal HIV infection increases the risk of SGA, but not preterm births, in this cohort.

Risk of Infant Mortality Among Twins in Relation to Placental Abruption: Contributions of Preterm Birth and Restricted Fetal Growth

While preterm birth and restricted fetal growth are strongly associated with infant mortality, the extent to which these associations are modified by placental abruption remains unknown. A retrospective cohort study was carried out to examine the risk of infant mortality among twins in relation to abruption, and explore the independent contributions of preterm birth and restricted fetal growth to these associations. The study was restricted to women who had delivered twins at 22 weeks' gestation or more and fetuses weighing 500 grams or more in the United States (1989–2000). Risks of preterm birth (less than 37 weeks' gestation), fetal growth restriction and infant mortality, in relation to placental abruption, were evaluated. All analyses were adjusted for potential sociodemographic confounding factors. The association between restricted twin fetal growth and abruption was the strongest among the most severely growth-restricted babies (i.e., less than 1 centile), with the strength of association diminishing with increasing birthweight centiles. The risk of preterm birth among pregnancies with and without abruption were 80.1% and 51.9%, respectively (relative risk [RR] 1.5, 95% confidence interval [CI] 1.4–1.6). The risk of small-for-gestational-age (SGA; birthweight of less than the 10th centile for gestational age) among abruption and nonabruption births was 11.7% and 9.2%, respectively (RR 1.3, 95% CI 1.2–1.4). Compared with twins of the appropriate growth delivered at term, the relative risks for infant mortality in the presence of abruption were 9.9 (95% CI 5.4–18.2) for term-SGA, 25.0 (95% CI 22.3–28.1) for preterm-non-SGA, and 36.2 (95% CI 28.4–46.1) for preterm-SGA births. The association between infant mortality and abruption among twins appears largely mediated through preterm birth, and to a lesser extent, through SGA. The association between fetal growth and abruption is strongest among the severely growth-restricted babies, suggesting that the origins of placental abruption may develop in early pregnancy.

Periconceptional multivitamin use and risk of preterm or small-for-gestational-age births in the Danish National Birth Cohort

BACKGROUND

The intake of periconceptional multivitamins may decrease the risk of preterm births (PTBs) or small-for-gestational-age (SGA) births.

OBJECTIVE

We related the timing and frequency of periconceptional multivitamin use to SGA births and PTBs and its clinical presentations (ie, preterm labor, premature rupture of membranes, and medical induction).

DESIGN

Women in the Danish National Birth Cohort (n = 35,897) reported the number of weeks of multivitamin use during a 12-wk periconceptional period. Cox regression was used to estimate the relation between any multivitamin use and PTBs (<37 wk) or SGA births (birth weight adjusted for gestational age >2 SDs below the mean on the basis of fetal growth curves). The timing (preconception and postconception) and frequency of use were also analyzed. Regular users (4-6 wk) and partial users (1-3 wk) in each period were compared with nonusers.

RESULTS

The association between periconceptional multivitamin use and PTBs varied according to prepregnancy overweight status (P-interaction = 0.07). Regular preconception and postconception multivitamin use in women with a prepregnancy BMI (in kg/m(2)) <25 was associated with reduced risks of a PTB (HR: 0.84; 95% CI: 0.73, 0.95) and preterm labor (HR: 0.80; 95% CI: 0.69, 0.94). No similar associations were shown for overweight women. The adjusted risk of an SGA birth was reduced in multivitamin users regardless of their prepregnancy BMI (HR: 0.83; 95% CI: 0.73, 0.95), with the strongest association in regular users in the postconception period.

CONCLUSION

Regular periconceptional multivitamin use was associated with reduced risk of SGA births and PTBs in nonoverweight women.

Reproductive outcomes among former Love Canal residents, Niagara Falls, New York

Love Canal, located in Niagara Falls, NY, and among the earliest and most significant hazardous waste sites in the United States, first came to public attention in 1978. In this study, researchers evaluated 1,799 live births from 1960 through 1996 to 980 women who formerly lived in the Love Canal Emergency Declaration Area and were of reproductive age sometime during that time period. Using Upstate New York and Niagara County as external comparison populations, standardized incidence ratios with 95% confidence intervals were calculated for low birth weight, preterm birth, small for gestational age, and congenital malformations, and unadjusted proportions of male to female births were calculated. Internal comparisons among the infants were also performed according to several measures of potential exposure using generalized estimating equations. The results indicated a statistically significant elevated risk of preterm birth among children born on the Love Canal prior to the time of evacuation and relocation of residents from the Emergency Declaration Area, using Upstate New York as the standard population (standardized incidence ratio=1.40; 95% confidence interval: 1.01, 1.90). Additionally, the ratio of male to female births was lower for children conceived in the Emergency Declaration Area (sex ratio=0.94 versus sex ratio=1.05 in the standard population) and the frequency of congenital malformations was greater than expected among Love Canal boys born from 1983 to 1996 (standardized incidence ratio=1.50 when compared to Upstate New York), although in both cases the 95% confidence interval included the null value. Finally, increased risk for low birth weight infants among mothers who lived closest to the Canal as children was found (odds ratio=4.68; 95% confidence interval: 1.24, 17.66), but this estimate was limited due to small numbers (n=4). The study adds to the knowledge of the possible reproductive effects from exposure to chemicals arising from hazardous waste; however, given the small number of some events, the qualitative nature of the exposure assessment, and possibility of spurious associations due to multiple comparisons, the findings should be interpreted cautiously.

Anxiety and optimism associated with gestational age at birth and fetal growth

Psychosocial factors such as anxiety or optimism may be related to the risk of adverse pregnancy outcomes, but the evidence is conflicting. We investigated the relation between maternal anxiety, optimism, gestational age and infant birth weight in a cohort of 667 nulliparous women from the Prenatal Exposures and Preeclampsia Prevention study, Pittsburgh PA. Women completed the Spielberger Trait Anxiety Inventory and the Life Orientation Test at 18 weeks gestation. Linear and logistic regression models assessed the relation of anxiety and optimism to gestational age, birth weight centile, preterm delivery (<37 weeks) or small for gestational age (<10th percentile) births. After adjustment for age, race, preeclampsia, and smoking, higher anxiety was associated with decreasing gestational age (-1.6 days per SD increase in anxiety score, P = 0.06). This relationship was modified by maternal race (P < 0.01 for interaction). Among African American women, each SD increase in anxiety was associated with gestations that were, on average, 3.7 days shorter (P = 0.03). African American women with anxiety in the highest quartile had gestations that were 8.2 days shorter, and they had increased risk for preterm birth after excluding cases of preeclampsia (OR 1.69, 95% CI 1.08, 2.64). There was no association between anxiety and gestational age among White women. There was also no relation between anxiety, optimism and birth weight centile. Trait anxiety was associated with a reduction in gestational age and increased risk for preterm birth among African American women. Interventions that reduce anxiety among African American pregnant women may improve pregnancy outcomes.

Maternal underweight and the risk of preterm birth and low birth weight: a systematic review and meta-analyses

BACKGROUND

Despite the current obesity epidemic, maternal underweight remains a common occurrence with potential adverse perinatal outcomes. Our objective was to determine the relationship between maternal underweight and preterm birth (PTB) and low birth weight (LBW) in singleton pregnancies in developing and developed countries.

METHODS

We followed the MOOSE consensus statement. We searched MEDLINE and EMBASE from their inceptions. We included studies that assessed the effect of maternal underweight compared with normal weight according to body mass index in singleton gestations on our two primary outcomes: PTB (<37 weeks) and LBW (<2500 g). Two assessors independently reviewed citations, extracted data and assessed quality.

RESULTS

A total of 78 studies were included involving 1 025 794 women. The overall risk of PTB was increased in the cohort studies of underweight women [adjusted relative risk (RR) 1.29, 95% confidence interval (CI) 1.15-1.46], as were the risks of spontaneous PTB (adjusted RR 1.32, 95% CI 1.10-1.57) and induced PTB (adjusted RR 1.21, 95% CI 1.07-1.36). Underweight women had an increased risk of an LBW infant (adjusted RR 1.64, 95% CI 1.38-1.94). In developed countries, underweight women had an increased risk of PTB (RR 1.22, 95% CI 1.15-1.30) but not in developing countries (RR 0.99, 95% CI 0.67-1.45). In both developed and developing countries, underweight women were at increased risk of having an LBW infant (RR 1.48, 95% CI 1.29-1.68, and RR 1.52, 95% CI 1.25-1.85, respectively).

CONCLUSIONS

In this systematic review and meta-analyses, we determined that singletons born to underweight women have higher risks of PTB (overall, spontaneous and induced) and LBW than those born to women with normal weight.

Parental occupation and preterm births: a nationwide epidemiological study in Sweden

The hypothesis was that some occupations could lead to preterm birth (PTB) because of potential exposures to various agents. The objective in this nationwide follow-up study was to analyse the association between PTB and parental occupational groups, controlling for potential confounders. Data from the Swedish Medical Birth Register, in which all children born in Sweden from 1990 onward are registered with their parents, were linked to census data. Inclusion criteria for the study population were employment (both women and men) and age >20 years (women). There were 816,743 first singleton live births from 1990 to 2004, of whom 43,956 were PTBs. A total of 7659 of the 43,956 PTBs were very PTBs. Odds ratios (ORs) with 95% confidence intervals were calculated separately for mothers and fathers to estimate the odds of PTB and very PTB in 51 occupational groups (reference groups: mothers or fathers who were 'Technical, science research-related workers and physicians') and by family income level. Women and men with low family incomes had increased ORs of PTB and very PTB. Significantly increased ORs of PTB (including very PTB) were found in four maternal and nine paternal occupational groups after accounting for family income, geographic region of residence, civil status, smoking habits, maternal age at infant's birth and period of birth. Further studies should examine specific agents in those parental occupations that were associated with increased odds of PTB and very PTB.

Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses

OBJECTIVE

To determine the relation between overweight and obesity in mothers and preterm birth and low birth weight in singleton pregnancies in developed and developing countries.

DESIGN

Systematic review and meta-analyses.

DATA SOURCES

Medline and Embase from their inceptions, and reference lists of identified articles.

STUDY SELECTION

Studies including a reference group of women with normal body mass index that assessed the effect of overweight and obesity on two primary outcomes: preterm birth (before 37 weeks) and low birth weight (<2500 g).

DATA EXTRACTION

Two assessors independently reviewed titles, abstracts, and full articles, extracted data using a piloted data collection form, and assessed quality.

DATA SYNTHESIS

84 studies (64 cohort and 20 case-control) were included, totalling 1 095 834 women. Although the overall risk of preterm birth was similar in overweight and obese women and women of normal weight, the risk of induced preterm birth was increased in overweight and obese women (relative risk 1.30, 95% confidence interval 1.23 to 1.37). Although overall the risk of having an infant of low birth weight was decreased in overweight and obese women (0.84, 0.75 to 0.95), the decrease was greater in developing countries than in developed countries (0.58, 0.47 to 0.71 v 0.90, 0.79 to 1.01). After accounting for publication bias, the apparent protective effect of overweight and obesity on low birth weight disappeared with the addition of imputed "missing" studies (0.95, 0.85 to 1.07), whereas the risk of preterm birth appeared significantly higher in overweight and obese women (1.24, 1.13 to 1.37).

CONCLUSIONS

Overweight and obese women have increased risks of preterm birth and induced preterm birth and, after accounting for publication bias, appeared to have increased risks of preterm birth overall. The beneficial effects of maternal overweight and obesity on low birth weight were greater in developing countries and disappeared after accounting for publication bias.

Preterm birth and psychiatric medication prescription in young adulthood: a Swedish national cohort study

BACKGROUND

Recent studies suggest an increased risk of adverse mental health outcomes among young adults who were born preterm. These studies have been based mainly on hospital data, thus missing large numbers of mental health problems that do not require inpatient treatment. We used national outpatient and inpatient pharmacy data to evaluate whether individuals who were born preterm were more likely to be prescribed psychiatric medications during young adulthood than individuals who were born full term.

METHODS

A national cohort of all infants born in Sweden from 1973 through 1979 [N = 635,933, including 28,799 who were born preterm (<37 weeks)] was followed to ages 25.5-34.0 years to determine whether psychotropic medications (antidepressants, antipsychotics, anxiolytics, hypnotics/sedatives and/or psychostimulants) were prescribed in 2005-06.

RESULTS

A trend of increasing rate of prescriptions for antipsychotics, antidepressants and hypnotics/sedatives in young adulthood was observed by earlier gestational age at birth. Young adults who were extremely preterm at birth (23-27 weeks) were 3.1 times more likely to be prescribed antipsychotics [95% confidence interval (CI) 1.66-5.93], 1.8 times more likely to be prescribed antidepressants (95% CI 1.26-2.64) and 1.8 times more likely to be prescribed hypnotics/sedatives (95% CI 1.15-2.96) than individuals who were full term at birth, after adjusting for potential confounders.

CONCLUSIONS

This national cohort study, using outpatient and inpatient pharmacy data, suggests that preterm birth has important independent effects on mental health that extend at least into young adulthood.

Parental occupation and risk of small-for-gestational-age births: a nationwide epidemiological study in Sweden

BACKGROUND

Although evidence suggests that some occupations may be a risk factor for small-for-gestational age (SGA) birth, associations between a wide range of maternal and paternal occupations and risk of SGA births remain unclear. Our objective was to analyze the risk of SGA births by parental occupation, including the entire Swedish population of mothers (> or =20 years) and fathers.

METHODS

We linked nationwide data (1990-2004) on singletons born to employed mothers to nationwide data on maternal and paternal occupation and other individual-level variables. Information on parental occupations was obtained from the 1990 census. Approximately 95% of SGA births (calculated using normative data) were defined on the basis of ultrasound. Odds ratios of SGA birth were calculated with 95% confidence intervals. Women and men were analyzed separately.

RESULTS

There were 816,310 first singleton live births during the study period, of which 29,603 were SGA events. Families with low incomes had an increased risk of SGA births. After accounting for maternal age at the infant's birth, period of birth, family income, region of residence, marital status and smoking habits, several maternal occupational groups (including 'mechanics and iron and metalware workers' and 'packers, loaders and warehouse workers') had a significantly higher risk of SGA birth than the reference group (all women in the study population). Among paternal occupational groups, only waiters had an increased risk of SGA birth.

CONCLUSIONS

This large-scale follow-up study shows that maternal occupation affects risk of SGA birth, whereas paternal occupation does not seem to have an impact on SGA birth. Further studies are required to examine the specific agents in those maternal occupations that are associated with an increased risk of SGA birth.

Body composition by dual-energy X-ray absorptiometry in women with previous pre-eclampsia or small-for-gestational-age offspring

OBJECTIVE

To investigate differences in body composition and fat distribution between women with previous pre-eclampsia or small-for-gestational-age (SGA) offspring and those with uncomplicated pregnancies.

DESIGN

Cohort study.

SETTING

Population-based study in a genetically isolated population in the southwest of the Netherlands.

POPULATION

Women after pregnancies complicated by pre-eclampsia (n=45), SGA offspring (n=53) and uncomplicated pregnancies (n=106).

METHODS

Women were compared for body composition and fat distribution variables, assessed by dual-energy X-ray absorptiometry (DXA) and anthropometrics at a mean follow-up time of 10.8 (SD +/- 5.9) years after pregnancy.

MAIN OUTCOME MEASURES

Total lean and fat mass, android fat mass, gynoid fat mass, android-to-gynoid fat ratio, waist and hip circumference, waist-to-hip ratio.

RESULTS

Women with previous pre-eclampsia compared with controls had higher mean total fat mass index (11.5 +/- 0.6 versus 9.7 +/- 0.4 kg/m(2); P = 0.03), lean mass index (15.8 +/- 0.3 versus 14.5 +/- 0.2 kg/m(2); P =0.001) and body mass index ([BMI]; 28.4 +/- 0.8 versus 25.4 +/- 0.5 kg/m(2); P = 0.005). Their waist circumferences (90.7 +/- 2.0 versus 78.5 +/- 1.3 cm; P < 0.001) and waist-to-hip ratios (0.86 +/- 0.01 versus 0.77 +/- 0.01; P < 0.001) were also higher as well as android fat mass (2.8 +/- 0.2 versus 2.1 +/- 0.1 kg; P = 0.01) and android-to-gynoid fat ratios (0.45 +/- 0.02 versus 0.39 +/- 0.01; P = 0.02). Mean total fat, lean and BMI was not significantly different between women with previous SGA offspring and controls, yet waist-to-hip ratios (0.83 +/- 0.01; P < 0.001) were higher. The observed differences in waist and hip circumference, waist-to-hip ratio and gynoid fat mass could not be attributed to differences in BMI.

CONCLUSION

Women with previous pre-eclampsia or SGA offspring pregnancies compared with those with uncomplicated pregnancies have a preferential fat accumulation in the abdominal over hip region, which may explain, at least partly, their increased cardiovascular risk.

Interactions between smoking and weight in pregnancies complicated by preeclampsia and small-for-gestational-age birth

Cigarette smoking protects against preeclampsia but increases the risk of small-for-gestational-age birth (SGA). Regarding body weight, the converse is true: obesity elevates rates of preeclampsia but reduces rates of SGA. The authors assessed the combined effects of smoking and weight among US women developing preeclampsia or SGA, studying 7,757 healthy, primigravid women with singleton pregnancies in 1959-1965. Smoking (never, light, heavy), stratified by prepregnancy body mass index (BMI (weight (kg)/height (m)(2)); underweight, overweight, obese), was examined in relation to preeclampsia and SGA. Among underweight (BMI <18.5) and normal-weight (BMI 18.5-24.9) women, smoking decreased the risk of preeclampsia (for heavy smoking, light smoking, nonsmoking, test for trend p = 0.002 for underweight and p = 0.009 for normal weight) after adjustment for age, race, and socioeconomic status. However, among overweight/obese women (BMI >or=25), this trend was not apparent (p = 0.4). Among both underweight and overweight women, smoking significantly increased SGA risk (trend p < 0.001 for underweight and p = 0.02 for overweight/obese). Obesity eliminated the inverse association between smoking and preeclampsia but did not substantially alter the positive association between smoking and SGA. A possible unifying biologic explanation is discussed in this paper.

Neighborhood economic disadvantage, violent crime, group density, and pregnancy outcomes in a diverse, urban population

Prior research has established associations between pregnancy outcomes and specific neighborhood characteristics, including economic disadvantage, violent crime, and racial/ethnic segregation. Recently, associations have also been found between various health outcomes and group density, the degree to which an individual is a racial or ethnic majority in his or her local community. The objective of this study was to determine the extent to which census tract economic disadvantage, violent crime rate, and group density are associated with pregnancy outcomes among White, Black, and Hispanic infants in a large metropolitan setting. This cross-sectional study utilized 1990 census data, 1991 crime data, and 1991 birth certificate information for singleton live births in Chicago, Illinois. Results show substantial racial segregation in Chicago, with 35% of census tracts having more than 90% Black residents and 45% of census tracts having fewer than 10% Black residents. After stratifying by maternal race/ethnicity, we used multilevel analyses to model pregnancy outcomes as a function of individual and census tract characteristics. Among all racial/ethnic groups, violent crime rate accounted for most of the negative association between tract economic disadvantage and birth weight. Group density was also associated with birth weight but this association was stronger among Whites and Hispanics than among Blacks. Further analysis revealed that group density was more strongly associated with preterm birth while violent crime rate was more strongly associated with small for gestational age. These results suggest that group density and violent crime may impact birth weight via different mechanisms.

Epidemiology and environmental factors in preterm labour

An epidemiological and environmental approach is the appropriate starting point to understanding preterm labour. Although there are multiple aetiologies it seems likely that anthropometric and environmental risk factors in combination with inherent genetic susceptibilities contribute to an increased risk of preterm labour for certain women. Poct 2pulation-based studies identifying risk factors and quantifying outcomes facilitate informed counselling and provide a framework for developing prediction tools. Carefully conducted case-control and cohort studies identify associations that may contribute to an understanding of causation. A combined approach encompassing epidemiology, pathophysiology and clinical research is required to understand the aetiologies, prevention and optimal management of preterm labour. This review focuses on the epidemiology of preterm labour and the role of environmental factors.

Comparison of Risk Factors for Small-for-Gestational-Age and Preterm in a Portuguese Cohort of Newborns

OBJECTIVE

To identify risk factors for small-for-gestational-age and preterm in a Portuguese cohort of newborns.

STUDY DESIGN

Socio-demographic, anthropometric, behavioural and obstetrical characteristics were evaluated in 4.193 women consecutively delivered. Term small-for-gestational-age (n = 342) and non-small-for-gestational-age preterm (n = 148) were compared to non-small-for-gestational-age term births (n = 3538). Adjusted odds ratios and etiologic fractions were calculated.

RESULTS

Low height, low weight when entering pregnancy and low weight gain were significantly associated with small-for-gestational-age, but not preterm. These were the factors with the highest etiologic fraction for small-for-gestational-age. An increased risk of small-for-gestational-age was found for women who smoked during pregnancy (OR = 2.39; 95% CI: 1.66-3.46) and began antenatal care after pregnancy first trimester (OR = 1.86; 95% CI: 1.32-2.62). Previous abortion was associated with small-for-gestational-age (OR = 1.72; 95% CI: 1.16-2.55) and previous preterm with preterm (OR = 3.20; 95% CI: 1.26-8.14).

CONCLUSIONS

Low anthropometrics, smoking and late antenatal care were risk factors for small-for-gestational-age, but not preterm. Maternal anthropometrics were the factors with the highest impact on small-for-gestational-age. No factor showed a great contribution to preterm birth.

Association Between Infant Birth Weight and Maternal Cardiovascular Risk Factors in the Health, Aging, and Body Composition Study

PURPOSE

Mothers who deliver a low-birth-weight (LBW) infant may themselves be at excess risk for cardiovascular disease. We investigated whether older women who bore LBW infants had higher blood pressure, lipid, glucose, insulin, interleukin 6 (IL-6), and C-reactive protein concentrations, and pulse wave velocity compared to women with normal-weight births.

METHODS

Participants were 446 women with a mean age of 80 years and 47% black. Women reported birth weight and complications for each pregnancy. Analysis was limited to first births not complicated by hypertension or preeclampsia.

RESULTS

Women who had delivered a first-birth infant weighing less than 2500 g had a lower body mass index (BMI) compared with women with a normal-weight (>or=2500 g) infant (26.7 versus 28.4 kg/m2; p=0.02), but they had a larger abdominal circumference for BMI (97.9 versus 95.5 cm; p=0.05). They also were marginally more likely to be administered antihypertensive medication (p=0.06). After adjustment for BMI, race, and age, women with a history of a small infant had elevations in systolic blood pressure (p=0.05) and greater IL-6 levels (p=0.02) and were more insulin resistant (p=0.05) compared with women with a normal-weight infant.

CONCLUSIONS

These findings suggest that a history of LBW delivery identifies women with elevated cardiovascular risk factors.

Impact of reproductive experience on women's smoking behaviour in Japanese nurses

OBJECTIVES

The objectives of this study were to describe current and past smoking behaviour of female Japanese nurses, to examine factors associated with developing and stopping a smoking habit, and to examine how their reproductive experiences affect their smoking behaviour.

STUDY DESIGN

A cross-sectional study. This study was a baseline survey of a prospective occupational cohort study.

METHODS

A self-administered survey of 1748 female Japanese nurses aged over 20 years was conducted in Gunma prefecture, Japan, in 1999.

RESULTS

Overall, 27.2% developed a smoking habit (current smokers, 19.8%; ex-smokers, 7.4%) and 72.2% were never smokers. Logistic regression analysis showed that the type of nursing certificate was statistically associated with developing a smoking habit. It also showed that the type of nursing certificate, work place, marital status and current pregnancy were statistically associated with smoking cessation. Currently pregnant women were more likely to stop smoking than non-pregnant women (adjusted odds ratio, 3.18; 95% confidence intervals, 1.25-8.06). For women aged 20-29 years, the proportions of current smokers, ex-smokers and never smokers among pregnant women were 11.5, 23.1 and 65.4%, respectively; among non-pregnant women of this age, the values were 22.3, 4.3 and 73.4%, respectively. There was a statistically significant difference in such proportions between the two groups (chi2=19.27; P<0.0001). More than half of the ex-smokers who were currently pregnant had stopped smoking in the last 12 months. Smoking behaviour showed no statistically significant difference between women who had had at least one delivery and women who had not.

CONCLUSIONS

The results suggest that pregnancy provides a good opportunity for smoking cessation, but a large proportion of women who successfully quit smoking during pregnancy relapse after delivery.

Shared and disparate components of the pathophysiologies of fetal growth restriction and preeclampsia

Intrauterine growth restriction (IUGR) and preeclampsia differ in their association with maternal disease but share a similar placental pathology. Moreover, mothers who have had pregnancies complicated by preeclampsia or IUGR are at elevated later-life cardiovascular risk. Why, then, do some women develop IUGR and others develop preeclampsia? In this clinical opinion, based on a review of the literature, we hypothesize that both women experiencing preeclampsia and IUGR enter pregnancy with some degree of endothelial dysfunction, a lesion that predisposes to shallow placentation. In our opinion, preeclampsia develops when abnormal placentation, through the mediator of elevated circulating cytokines, interacts with maternal metabolic syndrome, comprised of adiposity, insulin resistance/hyperglycemia, hyperlipidemia, and coagulopathy. IUGR develops in the absence of antenatal metabolic syndrome. Among these women, the baby is affected by shallow placentation but the mother does not develop clinically apparent disease. This conceptualization provides a testable framework for future etiologic studies of preeclampsia and IUGR.

Fetal growth and onset of delivery: a nationwide population-based study of preterm infants

OBJECTIVE

This study was undertaken to assess whether deviations from normal fetal growth are associated with spontaneous preterm delivery.

STUDY DESIGN

A population-based study was performed, using Swedish Medical Birth Register data from 1991 through 2001. The total population comprised 1,007,648 singleton births. Intrauterine-derived growth standards were used to identify individual standard deviation (SD) from expected birth weight. Spontaneous preterm infants were compared with infants born after spontaneous labor at term. Results were obtained by using multiple logistic regression analysis.

RESULTS

Associations between smaller than population mean and spontaneous preterm birth were evident for all gestational age groups. The largest risk was found at 28 to 31 gestational weeks and birth weight less than -3 SD (OR: 13.3; 95% CI: 10.3-17.2). Spontaneous preterm infants born at 34 to 36 gestational weeks weighed 1 to 1.9 SD (OR: 1.1; 95% CI: 1.1-1.2) or 2 to 2.9 SD (OR: 1.6; 95% CI: 1.5-1.7) above the expected mean more often.

CONCLUSION

Deviation of fetal growth from the expected mean is associated with spontaneous preterm delivery.

Smoking during pregnancy and preterm birth according to obstetric history: French national perinatal surveys

The relation between smoking and preterm delivery is not totally known. Our aim was to determine whether smoking during pregnancy was associated with preterm birth among women at different risk according to their obstetric history. The study was based on data from the 1998 French national perinatal survey. Of the 13073 singleton live births, 4.7% were preterm; 15% of the pregnant women were moderate (one to nine cigarettes per day) and 10% heavy smokers (at least 10 cigarettes per day). Smoking heavily was related to preterm birth (crude odds ratio [OR] = 1.35, 95% confidence interval [95% CI]: [1.04, 1.74]). Multivariable logistic regression showed a relation between smoking and preterm birth among multiparae without previous adverse pregnancy outcomes; the associated adjusted ORs (AORs) were 1.25 [95% CI 0.83, 1.87] among moderate smokers and 1.46 [95% CI 0.98, 2.20] among heavy smokers. The corresponding AORs were 0.69 [95% CI 0.46, 1.05]) and 0.96 [95% CI 0.59, 1.56] for primiparae and 1.11 [95% CI 0.63, 1.93] and 0.50 [95% CI 0.25, 0.98] for multiparae with previous adverse pregnancy outcomes. Our study showed a relation between heavy smoking during pregnancy and preterm birth mostly for women with low obstetric risk.

Differential effects of seasonality on preterm birth and intrauterine growth restriction in rural Africans

BACKGROUND

Low birth weight (LBW) can result from prematurity or intrauterine growth restriction (IUGR) and result in small-for-gestational-age (SGA) infants. Prematurity and IUGR may have different etiologies and consequences.

OBJECTIVE

Our objective was to analyze seasonal patterns of prematurity and SGA in a rural African community and to compare them against variations in nutritional and ecologic variables that may provide insight into likely causative factors.

DESIGN

Fourier series were used to compare the seasonality of prematurity (<37 wk) and SGA (<10th percentile of the reference standard) among 1916 live infants born over 26 y in 3 Gambian villages. The resultant patterns were compared against monthly variations in birth frequency, maternal energy status, maternal work, and malaria infections.

RESULTS

The incidence of LBW was 13.3%, of prematurity was 12.3%, and of SGA was 25.1%. Prematurity and SGA showed divergent patterns of seasonality. Incidence of SGA was highest at the end of the annual hungry season, from August to December (peaking in November at 30.6%), with a nadir of 12.9% in June. Rates of SGA varied inversely with maternal weight changes. This pattern was not seen for rates of prematurity, which showed 2 peaks-in July (17.2%) and October (13.9%). The lowest proportion of preterm births occurred in February (5.1%). The peaks in prematurity closely paralleled increases in agricultural labor (July) and malaria infections (October).

CONCLUSION

We conclude that a reduction in LBW in such communities may require multiple interventions because of the variety of precipitating factors.