Concordance among measures of pregnancy outcome based on fetal size and duration of gestation

Executive function deficits in children born preterm or at low birthweight: a meta-analysis

AIM

To investigate the magnitude of executive function deficits and their dependency on gestational age, sex, age at assessment, and year of birth for children born preterm and/or at low birthweight.

METHOD

PubMed, PsychINFO, Web of Science, and ERIC were searched for studies reporting on executive functions in children born preterm/low birthweight and term controls born in 1990 and later, assessed at a mean age of 4 years or higher. Studies were included if five or more studies reported on the same executive function measures.

RESULTS

Thirty-five studies (3360 children born preterm/low birthweight, 2812 controls) were included. Children born preterm/low birthweight performed 0.5 standardized mean difference (SMD) lower on working memory and cognitive flexibility and 0.4 SMD lower on inhibition. SMDs for these executive functions did not significantly differ from each other. Meta-regression showed that heterogeneity in SMDs for working memory and inhibition could not be explained by study differences in gestational age, sex, age at assessment, or year of birth.

INTERPRETATION

Children born preterm/low birthweight since 1990 perform half a SMD below term-born peers on executive function, which does not seem to improve with more recent advances in medical care or with increasing age.

WHAT THIS PAPER ADDS

Children born preterm/low birthweight perform below term-born children on core executive functions. Lower gestational age or male sex are not risk factors for poorer executive functions. Executive function difficulties in children born preterm/low birthweight remain stable across childhood. Executive function difficulties are similar for children born recently and children born in earlier eras.

Lessons learnt from enrolment and follow up of pregnant women and their infants in clinical trials in South Africa, a low-middle income country

INTRODUCTION

Infectious causes are a significant contributor to morbidity and mortality in neonates and young infants. Immunization of pregnant women to protect the mother and/or her infant is gaining momentum due to the benefits of this strategy demonstrated in numerous implemented strategies (Maternal and Neonatal Tetanus Elimination Initiative) and clinical trials. Reluctance by regulators, participants and healthcare providers to include pregnant women in clinical trials is considerable, but reducing. Infectious disease burden, and therefore need for interventions to reduce morbidity and mortality in mothers and infants, is highest in low-middle income countries (LMIC), however, reliable background data on adverse pregnancy outcomes and lack of experience in clinical trials and community opinions on immunization during pregnancy are not well documented.

METHODS

We used our experiences in conducting two clinical studies in pregnant women in South Africa to illustrate the challenges experienced and lessons learnt which may benefit others working in the maternal immunization field.

RESULTS

Accurate gestational age assessment, which is essential for clinical trials, is challenging in LMIC due to limited access to early ultrasound examinations, and unreliable assessment by history (last menstrual period date) and physical examination (symphyseal-fundal height). Concomitant administration of recommended vaccines has previously been avoided in clinical trials; however, this limitation could impact the potentially beneficial interventions that participants can access during antenatal care. Women in LMIC have a higher burden of concomitant illnesses (e.g. HIV infection, malaria and anaemia) and adverse pregnancy outcomes (e.g. stillbirth) than pregnant women in higher income countries. Availability of local data is essential for safety monitoring committees to identify vaccine-related adverse event triggers.

CONCLUSION

Immunization of pregnant women to reduce disease burden in them and their infants is promising, and women in high-risk settings should be included in trials (Clinical trial registry number: 'Study A': NCT01193920, 'Study B': NCT01888471).

Trihalomethanes in public drinking water and stillbirth and low birth weight rates: an intervention study

During 2003-2004, United Utilities water company in North West England introduced enhanced coagulation (EC) to four treatment works to mitigate disinfection by-product (DBP) formation. This enabled examination of the relation between DBPs and birth outcomes whilst reducing socioeconomic confounding. We compared stillbirth, and low and very low birth weight rates three years before (2000-2002) with three years after (2005-2007) the intervention, and in relation to categories of THM change. We created exposure metrics for EC and trihalomethane (THM) concentration change (n=258 water zones). We linked 429,599 live births and 2279 stillbirths from national birth registers to the water zone at birth. We used Poisson regression to model the differences in birth outcome rates with an interaction between before/after the intervention and EC or THM change. EC treatment reduced chloroform concentrations more than non-treatment (mean -29.7 µg/l vs. -14.5 µg/l), but not brominated THM concentrations. Only 6% of EC water zones received 100% EC water, creating exposure misclassification concerns. EC intervention was not associated with a statistically significant reduction in birth outcome rates. Areas with the highest chloroform decrease (30 - 65 μg/l) had the greatest percentage decrease in low -9 % (-12, -5) and very low birth weight -16% (-24, -8) rates. The interaction between before/after intervention and chloroform change was statistically significant only for very low birth weight, p=0.02. There were no significant decreases in stillbirth rates. In a novel approach for studying DBPs and adverse reproductive outcomes, the EC intervention to reduce DBPs did not affect birth outcome rates. However, a measured large decrease in chloroform concentrations was associated with statistically significant reductions in very low birth weight rates.

Exposure to trihalomethanes in drinking water and small-for-gestational-age births

BACKGROUND

Trihalomethanes in drinking water have been associated with higher occurrence of small-for-gestational-age (SGA) births, although results have been inconsistent.

METHOD

We geocoded residential address for mother of live, singleton, term births to 33 water distribution systems in a large metropolitan area of New South Wales, Australia (314,982 births between 1998 and 2004) and classified births into <10th percentile and ≥ 10 percentile of weight for gestational age. Mean trihalomethane exposure was estimated by trimester and for the entire pregnancy based on monthly sampling in each of the 33 water distribution systems. We estimated the relative risk (RR) of SGA for exposure to trihalomethanes using log-binomial regression adjusting for confounding.

RESULTS

SGA births increased with mother's third-trimester exposure to chloroform (RR = 1.04 [95% confidence interval = 1.02-1.06], across an interquartile range [IQR] = 25 μg/L) and bromodichloromethane (1.02 [1.01-1.04], 5 μg/L). Larger associations were found for SGA less than third percentile. Smoking modified the effects of trihalomethane exposure, with generally larger associations in births to nonsmoking mother and weaker or protective associations in births to smoking mothers.

CONCLUSIONS

: Mothers' exposures during pregnancy to total trihalomethane as well as to chloroform and bromodichloromethane were associated with SGA. These associations were modified by maternal smoking during pregnancy.

Increased risk of adverse pregnancy outcomes among women affected by herpangina

OBJECTIVE

This population-based study aimed to assess the relation between herpangina and adverse pregnancy outcomes: low birthweight (LBW), small for gestational age (SGA), and preterm delivery.

STUDY DESIGN

A total of 242 pregnant women who had singleton births and who visited ambulatory care centers for the treatment of herpangina were assessed, together with 1936 matched women as a comparison group. Conditional logistic regression analyses were performed to examine the risk of LBW, preterm birth, and SGA for mothers with herpangina and unaffected mothers.

RESULTS

Compared with pregnant women without herpangina, herpangina was associated with a 2.29- (95% confidence interval [CI], 1.42-3.69), 1.67- (95% CI, 1.04-2.68), and 1.63-fold (95% CI, 1.14-2.33) increased risk of having LBW, preterm, and SGA infants, respectively, after adjusting for family income and maternal and infant characteristics.

CONCLUSION

Our findings highlight a significant potential risk posed by herpangina, a usually mild disease, among pregnant women.

Increased risk of low birthweight, infants small for gestational age, and preterm delivery for women with peptic ulcer

OBJECTIVE

The objective of the study was to determine whether maternal peptic ulcer disease (PUD) is associated with increased risk of adverse pregnancy outcomes, using a nationwide population-based dataset.

STUDY DESIGN

We identified a total of 2120 women who gave birth from 2001 to 2003 with a diagnosis of PUD during pregnancy. Then 10,600 unaffected pregnant women were matched with cases in age and year of delivery. Multivariate logistic regression analyses were performed for estimation.

RESULTS

We found that PUD was independently associated with a 1.18-fold risk of low birthweight (95% confidence interval [CI], 1.01-1.30), a 1.20-fold risk of preterm delivery (95% CI, 1.02-1.41), and a 1.25-fold (95% CI, 1.11-1.41) higher risk of babies small for gestational age, compared with unaffected mothers, after adjusting for potential confounders. In further examining women with treated PUD, improved effects of PUD medication on the risks of adverse neonate outcomes were not identified.

CONCLUSION

We document increased risk of adverse birth outcomes for women with PUD during pregnancy.

Prematurity as a predictor of childhood asthma among low-income children

PURPOSE

The purpose of this study was to evaluate the association among birth weight, prematurity, and the prevalence of asthma later in childhood and to assess the degree to which this association may differ between black and white children.

METHODS

Michigan Medicaid claims data from 2001 through 2003 were analyzed to determine asthma prevalence for 150,204 children between ages 5 and 18 years. Asthma cases were identified using Healthcare Effectiveness Data and Information Set persistent asthma criteria and included children having claims for any of the following services within a calendar year: at least one inpatient or one emergency department (ED) claim with an asthma primary diagnosis; at least four asthma medication-dispensing events; or at least four outpatient visits with an asthma diagnosis, and at least two asthma medication-dispensing events. Birth weight and gestational age from birth certificate data were matched with Medicaid files to determine size-for-gestational-age criteria.

RESULTS

Overall, 8.3% of children had persistent asthma; black children had slightly higher asthma prevalence (8.6%) than white children (7.8%; odds ratio [OR]=1.11, 95% confidence interval [CI]: 1.07-1.15). Children born very preterm (<or=32 weeks) had higher prevalence of childhood asthma (11.7%) compared with term births (8.0%; OR=1.51, 95% CI: 1.40-1.63). However, no significant differences were observed in odds of asthma between black and white children born very preterm, preterm (33-36 weeks), or small for gestational age (SGA).

CONCLUSIONS

Regardless of race, children born very preterm had an increased risk of childhood asthma. Although overall asthma prevalence is higher among black children enrolled in Medicaid compared with their white counterparts, these differences were attenuated when prematurity or SGA status were taken into account.

Particulate air pollution and fetal health: a systematic review of the epidemiologic evidence

BACKGROUND

Research on the potential impact of air pollution on the health of adults and children has grown rapidly over the last decade. Recent studies have suggested that air pollution could also be associated with adverse effects on the developing fetus. This systematic review evaluates the current level of epidemiologic evidence on the association between ambient particulate air pollution and fetal health outcomes. We also suggest further research questions.

METHODS

Using database searches and other approaches, we identified relevant publications published between 1966 and 2001 in English. Articles were included if they reported original data on birthweight, gestational age at delivery, or stillbirth related to directly measured nonaccidental exposure to particulate matter.

RESULTS

Twelve studies met the inclusion criteria. There was little consistency in the evidence linking particulate air pollution and fetal outcomes. Many studies had methodologic weaknesses in their design and adjustment for confounding factors. Even in well-designed studies, the reported magnitude of the effects was small and inconsistently associated with exposure at specific stages of pregnancy.

CONCLUSIONS

The currently available evidence is compatible with either a small adverse effect of particulate air pollution on fetal growth and duration of pregnancy or with no effect. Further research should be directed toward clarifying and quantifying these possible effects and generating testable hypotheses on plausible biologic mechanisms.

Incidence of and socio-demographic risk factors for stillbirth, preterm birth and low birthweight among Zimbabwean women

Data on birth outcomes are important for planning maternal and child health care services in developing countries. Only a few studies have examined frequency of birth outcomes in Zimbabwe, none of which has jointly examined the spectrum of poor birth outcomes across important demographic subgroups. We assessed delivery patterns and birth outcomes in 17 174 births over a one-year period from October 1997 to September 1998 at Harare Hospital, Zimbabwe. The annual rate of stillbirth was 61 per 1000 live births, rate of preterm birth (<37 weeks) was 168 per 1000, and low birthweight (LBW) (<2500 g) was 199 per 1000. Not attending antenatal care (prenatal care) was associated with increased risks of stillbirth [relative risk (RR) = 2.54, 95% CI 2.21, 2.92], preterm delivery [RR = 2.43, 95% CI 2.26, 2.61] and LBW births [RR = 2.16, 95% CI 2.02, 2.31]. Preterm births and LBW births were more likely to be stillborn [RR = 7.26, 95% CI 6.28, 8.39 and RR = 6.85, 95% CI 5.94, 7.91]. In conclusion, the rate of stillbirth is high and is predominantly associated with preterm births and to a lesser extent LBW. Reducing the frequency of stillbirth will require a better understanding of the determinants of preterm births and strategies for addressing this particular subset of high-risk births.

Arsenic exposure from drinking water and birth weight

BACKGROUND

Arsenic exposures from drinking water increase the risk of various cancers and noncancer health endpoints. Limited evidence suggests that arsenic may have adverse human reproductive effects. We investigated the association between drinking water arsenic exposure and fetal growth, as manifest in birth weight.

METHODS

We conducted a prospective cohort study in two Chilean cities with contrasting drinking water arsenic levels: Antofagasta (40 micro g/L) and Valparaíso (<1 micro g/L). Study subjects completed in-depth interviews and provided urine samples for exposure analysis. We obtained pregnancy and birth information from medical records. The birth weight analysis was restricted to liveborn, singleton infants born between December 1998 and February 2000.

RESULTS

The final study group consisted of 424 infants from Antofagasta and 420 from Valparaíso. After controlling for confounders, results of the multivariable analysis indicated that Antofagasta infants had lower mean birth weight (-57 g; 95% confidence interval = -123 to 9).

CONCLUSION

This study suggests that moderate arsenic exposures from drinking water (<50 micro g/L) during pregnancy are associated with reduction in birth weight, similar in magnitude to that resulting from other environmental exposures such as environmental tobacco smoke and benzene.

Adverse birth outcomes in relation to prenatal sonographic measurements of fetal size

OBJECTIVE

To evaluate and quantify the prediction of multiple neonatal outcomes by sonographically estimated fetal weight across a broad range of gestational ages.

METHODS

A retrospective cohortanalysis was conducted among women with certain gestational age (n = 1,376) seen at the University of California San Francisco from 1994 through 1997. The relative risks for small size at birth, small (low birth weight) for gestational age, and adverse neonatal outcomes were compared between small and average-sized fetuses.

RESULTS

Fetuses with an estimated fetal weight in the 5th percentile or less for gestational age were at increased risk of a birth weight less than 2,000 g (relative risk, 6.5), a birth weight in less than the 3rd percentile for gestational age (relative risk, 10.1), preterm birth (relative risk, 2.2), extreme preterm birth (relative risk, 5.7), prolonged neonatal hospital stay (relative risk, 2.7), neonatal intensive care unit admission (relative risk, 3.2), and stillbirth or neonatal death (relative risk, 7.7) compared with average-sized fetuses (all P < .0001). With intrauterine growth restriction defined as an estimated fetal weight in the 5th percentile or less for gestational age, up to 29% of fetuses with adverse neonatal outcomes were detected, for false-positive rates of only 4% to 5%. After adjusting for confounding variables, low estimated fetal weight remained a significant predictor of neonatal morbidity and mortality.

CONCLUSIONS

Morbidity and mortality are significantly increased among fetuses with an estimated fetal weight in the 5th percentile or less for gestational age.

US evaluation of fetal growth: prediction of neonatal outcomes

PURPOSE

To determine whether fetal growth measured at serial ultrasonographic (US) examinations can predict neonatal morbidity, independent of whether gestational age is known.

MATERIALS AND METHODS

Women (n = 321) who had singleton pregnancies and underwent two or more second- or third-trimester obstetric US examinations were included in a retrospective cohort analysis. Inadequate fetal growth was defined as growth at or below the 10th percentile. The relative risk of each poor outcome was calculated for fetuses with inadequate growth, compared with the risk for fetuses with normal growth.

RESULTS

Inadequate fetal growth was associated with 3.9 times the risk of a birth weight less than 2,500 g, 17.7 times the risk of a birth weight less than the 3rd percentile for gestational age, 2.3 times the risk of preterm birth, 2.6 times the risk of a long newborn hospital stay, and 3.6 times the risk of neonatal intensive care unit admission. After adjusting for confounding variables, including fetal weight, fetal growth remained a significant predictor of small birth size and poor outcomes. Inadequate growth predicted the risk of poor outcomes, even when gestational age was unknown. When inadequate growth was used to identify fetuses at risk, 21%-67% of neonates who were small at birth or had poor outcomes were identified at false-positive rates of only 5%-9%. For all outcomes, inadequate growth enabled identification of more fetuses with poor birth outcomes than low estimated fetal weight.

CONCLUSION

Morbidity is significantly increased among fetuses who demonstrate less than expected growth. Growth between two US examinations can be used to estimate the risk of neonatal morbidity, even when gestational age is unknown.

Associations of polycyclic organic matter in outdoor air with decreased birth weight: a pilot cross-sectional analysis

The association between births that are small for gestational age and outdoor airborne polycyclic organic matter (POM) was examined in New Jersey, a highly urban state. This pilot study utilizes a cross-sectional investigation combining maternal and pregnancy outcome information from birth certificates with air toxics data from the U.S. Environmental Protection Agency Cumulative Exposure Project and census data at the census tract level. The exposure categories were based on tertiles of modeled average POM concentrations for each census tract in New Jersey. High POM exposure was positively associated with delivery of "small for gestational age" (SGA) births. After adjustment for potential individual-level confounding factors, the odds ratios for term, preterm, and all SGA were 1.22 (1.16-1.27), 1.26 (1.07-1.49), and 1.22 (1.17-1.27), respectively, for the highest exposure tertile in the urban population of the state (89% of the state's birth population). For group-level variables, the corresponding ORs were 1.12 (1.07-1.18), 1.23 (1.02-1.47), and 1.13 (1.07-1.18). The results of this study suggest that residential exposure to airborne polycyclic organic matter (POM) is associated with increased prevalence of "small for gestational age" births among urban population. Cross-sectional investigations combining air dispersion models with routinely collected population-based health and census data could be a useful approach for identifying the hazardous air pollutants of greatest public health concern.