Birth weight and smoking during pregnancy--effect modification by maternal age

Maternal smoking status during pregnancy and low birth weight in offspring: systematic review and meta-analysis of 55 cohort studies published from 1986 to 2020

BACKGROUND

Maternal smoking during pregnancy may be associated with low birth weight (LBW) in offspring and global risk estimates have not been summarized previously. We aimed to systematically explore evidence regarding maternal smoking and the LBW risk in offspring globally and examine possible causes of heterogeneity across relevant studies.

METHODS

Comprehensive search of PubMed, Ovid Embase, Ovid Medline (R), and Web of science from inception until October 2021 was carried out. A random-effects meta-analysis was used to estimate the pooled odds ratio (OR) and corresponding 95% confidence interval (CI). Restricted cubic spline analysis with three knots was used to further examine the dose-response relationship.

RESULTS

Literature searches yielded 4940 articles, of which 53 met inclusion criteria (comprising 55 independent studies). Maternal smoking during pregnancy was significantly associated with the risk of LBW in offspring (OR = 1.89, 95% CI = 1.80-1.98). Furthermore, an obvious dose-response relationship between the amount of cigarettes daily smoked in pregnancy and the risk of LBW in offspring was observed. The results of subgroup analyses indicated that the risk of maternal smoking on LBW was larger in more recently conducted studies (P = 0.020) and longer period of active smoking during pregnancy (P = 0.002). No evidence of publication bias was found.

CONCLUSIONS

In summary, maternal smoking in pregnancy was significantly associated with a higher risk of LBW in offspring on a global scale. The risk of maternal smoking on infant LBW seems to be increasing over time, and was higher with longer smoking duration throughout pregnancy and more cigarettes smoked daily.

Impact of maternal HIV infection on pregnancy outcomes in southwestern China - a hospital registry based study

Globally, human immune deficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) continues to be a major public health issue. With improved survival, the number of people living with HIV/AIDS is increasing, with over 2 million among pregnant women. Investigating adverse pregnant outcomes of HIV-infected population and associated factors are of great importance to maternal and infant health. A cross-sectional data collected from hospital delivery records of 4397 mother-infant pairs in southwestern China were analysed. Adverse pregnant outcomes (including low birthweight/preterm delivery/low Apgar score) and maternal HIV status and other characteristics were measured. Two hundred thirteen (4.9%) mothers were HIV positive; maternal HIV infection, rural residence and pregnancy history were associated with all three indicators of adverse pregnancy outcomes. This research suggested that maternal population have high prevalence in HIV infection in this region. HIV-infected women had higher risks of experiencing adverse pregnancy outcomes. Rural residence predisposes adverse pregnancy outcomes. Findings of this study suggest social and medical support for maternal-infant care needed in this region, selectively towards rural areas and HIV-positive mothers.

Air pollution, neighbourhood and maternal-level factors modify the effect of smoking on birth weight: a multilevel analysis in British Columbia, Canada

Background

Maternal smoking during pregnancy negatively impacts fetal growth, but the effect is not homogenous across the population. We sought to determine how the relationship between cigarette use and fetal growth is modified by the social and physical environment.

Methods

Birth records with covariates were obtained from the BC Perinatal Database Registry (N = 232,291). Maternal smoking status was self-reported as the number of cigarettes smoked per day usually at the first prenatal care visit. Census dissemination areas (DAs) were used as neighbourhood-level units and linked to individual births using residential postal codes to assign exposure to particulate air pollution (PM_2.5) and neighbourhood-level attributes such as socioeconomic status (SES), proportion of post-secondary education, immigrant density and living in a rural place. Random coefficient models were used with cigarettes/day modeled with a random slope to estimate its between-DA variability and test cross-level interactions with the neighbourhood-level variables on continuous birth weight.

Results

A significant negative and non-linear association was found between maternal smoking and birth weight. There was significant between-DA intercept variability in birth weight as well as between-DA slope variability of maternal smoking on birth weight of which 68 and 30 % respectively was explained with the inclusion of DA-level variables and their cross-level interactions. High DA-level SES had a strong positive association with birth weight but the effect was moderated with increased cigarettes/day. Conversely, heavy smokers showed the largest increases in birth weight with rising neighbourhood education levels. Increased levels of PM_2.5 and immigrant density were negatively associated with birth weight, but showed positive interactions with increased levels of smoking. Older maternal age and suspected drug or alcohol use both had negative interactions with increased levels of maternal smoking.

Conclusion

Maternal smoking had a negative and non-linear dose-response association with birth weight which was highly variable between neighbourhoods and evidence of effect modification with neighbourhood-level factors. These results suggest that focusing exclusively on individual behaviours may have limited success in improving outcomes without addressing the contextual influences at the neighbourhood-level. Further studies are needed to corroborate our findings and to understand how neighbourhood-level attributes interact with smoking to affect birth outcomes.

Association between Maternal Smoking during Pregnancy and Low Birthweight: Effects by Maternal Age

Background

Maternal smoking during pregnancy has been consistently related to low birthweight. However, older mothers, who are already at risk of giving birth to low birthweight infants, might be even more susceptible to the effects of maternal smoking. Therefore, this study aimed to examine the modified association between maternal smoking and low birthweight by maternal age.

Methods

Data were obtained from a questionnaire survey of all mothers of children born between 2004 and 2010 in Okinawa, Japan who underwent medical check-ups at age 3 months. Variables assessed were maternal smoking during pregnancy, maternal age, gestational age, parity, birth year, and complications during pregnancy. Stratified analyses were performed using a logistic regression model.

Results

In total, 92641 participants provided complete information on all variables. Over the 7 years studied, the proportion of mothers smoking during pregnancy decreased from 10.6% to 5.0%, while the prevalence of low birthweight did not change remarkably (around 10%). Maternal smoking was significantly associated with low birthweight in all age groups. The strength of the association increased with maternal age, both in crude and adjusted models.

Conclusions

Consistent with previous studies conducted in Western countries, this study demonstrates that maternal age has a modifying effect on the association between maternal smoking and birthweight. This finding suggests that specific education and health care programs for older smoking mothers are important to improve their foetal growth.

Alcohol, tobacco, cocaine, and marijuana use: relative contributions to preterm delivery and fetal growth restriction

BACKGROUND

Pregnancy substance use is linked to low birth weight. However, less is known about relative contributions of various substances and whether effects are due to decreased gestational duration, restriction of fetal growth, or both. The study goal was to use causal modeling to evaluate the individual impact of alcohol, tobacco, cocaine, and marijuana on gestational duration and fetal growth.

METHODS

Participants were 3164 urban black women recruited at entry to prenatal care and followed to delivery, with all gestational dating ultrasound supported. Pregnancy substance use was assessed via self-report (alcohol, tobacco, cocaine, and marijuana).

RESULTS

Alcohol, cigarette, and cocaine use were all individually and negatively related to gestational age at delivery. However, only alcohol, cigarette, and marijuana use predicted fetal growth, with effects for alcohol and cigarette greater and more discrepant for older women. Overall, heavy cigarette smoking had the greatest individual impact on birth weight (up to 431 g). Heavy levels of use of all 4 substances by older women decreased birth weight by 26% (806 g).

CONCLUSIONS

For perhaps the first time, reduced birth weight is apportioned both by type of substance and mechanism of effect. The use of alcohol and/or cigarettes was clearly more harmful to fetal growth than cocaine use. Findings demonstrate the need for continued emphasis on intervention efforts to address legal and illicit pregnancy substance use.

Adverse pregnancy outcomes and subsequent risk of cardiovascular disease in women with systemic lupus erythematosus

Background/objective

Patients with systemic lupus erythematosus (SLE) are at increased risk for adverse pregnancy outcomes and cardiovascular disease (CVD). The objective of this exploratory study was to investigate the association between a history of adverse pregnancy outcomes and subsequent risk of subclinical CVD assessed by imaging studies and verified clinical CVD events in 129 women with SLE.

Methods

The occurrence of adverse pregnancy outcomes, specifically pre-eclampsia, preterm birth and low birth weight was ascertained by questionnaire. Subclinical CVD was assessed by coronary artery calcium (CAC) as measured by electron beam CT and carotid plaque measured by B mode ultrasound. Clinical CVD events were verified by medical record review. Logistic regression was used to estimate the association of pregnancy complications with occurrence of subclinical CVD and clinical CVD with a priori adjustment for age, which is associated with CVD and SLE disease duration as a measure of SLE disease burden.

Results

Fifty-six women reported at least one pregnancy complication while 73 had none. Twenty-six women had at least one pregnancy complicated by pre-eclampsia and were more likely to have a CAC score greater than or equal to 10 (adjusted OR=3.7; 95% CI 1.2 to 11.9), but the presence of plaque was not associated with this pregnancy complication, OR=1.1, (95% CI 0.4 to 2.8). Low birth weight and preterm birth were not associated with CAC or plaque.

Conclusions

Patients with SLE with a history of pre-eclampsia had a higher rate of subclinical CVD as measured by CAC score. Future studies are needed to confirm the relationship between adverse pregnancy outcomes and subsequent subclinical CVD and clinical CVD events.

Smoking among older childbearing women - a marker of risky health behaviour a registry-based study in Finland

BACKGROUND

Smoking during pregnancy is known to negatively affect pregnancy outcomes and it has been associated with numerous complications during pregnancy. Smoking is more common in younger pregnant women, but previous research has shown that adverse pregnancy outcomes related to older maternal age and smoking are even more harmful than with younger smokers. The aim of this study was to compare pregnancy outcomes among smoking and non-smoking pregnant women aged <35 years and ≥35 years.

METHODS

In this registry-based study, the data were collected from three national Finnish health registries: Finnish Medical Birth Register, Finnish Hospital Discharge Register, and Register of Congenital Malformations between the years 1997 and 2008. The data included information on 80 260 women who were smoking during pregnancy, of which 11 277 (9%) were ≥35 years and 68 983 (13%) were <35 years old. In multivariate modelling, the main outcome measures were preterm delivery, low Apgar scores at 1 min., low birth weight, small for gestational age, fetal death and preeclampsia.

RESULTS

Fewer older women smoked during pregnancy (9%) than younger women did (13%). Smoking increased the risk of adverse pregnancy outcomes, most in the older group. Multivariate logistic regression using non-smoking women aged <35 years as a reference group indicated that smoking women <35 years had higher rates of preterm delivery (OR 1.27 CI 1.20-1.35), SGA (OR 2.18 CI 2.10-2.26) and LBW (OR 1.73 CI 1.62-1.84).Non-smoking women ≥35 had higher rates of preterm delivery (OR 1.15 CI 1.10-1.20), fetal death (OR 1.36 CI 1.12-1.64), preeclampsia (OR 1.14 CI 1.09-1.20) and LBW (OR 1.13 CI 1.07-1.19).Smoking women ≥35 had higher rates of preterm delivery (OR 1.60 CI 1.40-1.82), SGA (OR 2.55 CI 2.34-2.79), fetal death (OR 2.70 CI 1.80-4.05) and LBW (OR 2.50 CI 2.20-2.80).

CONCLUSIONS

Smoking during pregnancy increased the risk of adverse pregnancy outcomes in all women, but the rates were the highest for women aged ≥35 years. Pregnant women aged ≥35 years smoking during pregnancy was a distinctly high risk group. Maternity care should identify these women and support them in cessation of smoking during the first trimester of 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.

Effects of smoking during pregnancy on the optic nerve neurodevelopment

BACKGROUND

Tobacco smoking during pregnancy alters neurodevelopment. Optical coherence tomography (OCT) provides precise measurements of the retinal nerve fiber layer (RNFL), which forms part of the central nervous system.

AIMS

To assess using the OCT how smoking during pregnancy would affect optic nerve development as detected in human offspring.

STUDY DESIGN

Visual examination and OCT were performed on a group of children (n=70; 4.15-13.50 years of age), classified as being exposed or not to maternal smoking during gestational period. The association between smoking during pregnancy and RNFL thickness was assessed by a linear regression analysis adjusted for possible confounding factors.

RESULTS

Although visual outcomes did not differ between groups, a significant decrease in the RNFL thickness was found in the group of infants exposed to smoke (105.3 vs 95.6; p=0.002), even when adjusting for gestational age, birth weight or gender.

CONCLUSIONS

OCT measurements show that intrautero exposure to tobacco smoke interferes with the development of the optic nerve.

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.

Effect of psychosocial stress and physical activity on low birthweight: a cohort study

AIM

To determine the effect of physical activity and psychosocial stress on low birthweight (LBW).

METHODS

A prospective study was carried out in a district of Sri Lanka between May 2001 and April 2002. A total of 885 pregnant mothers were recruited at < or = 16 weeks of gestation and followed up until partus. Trimester-specific exposure statuses along with potential confounding factors were gathered on average at the 12th, 28th, and 36th weeks of gestation. Physical activities were assessed by inquiring about the duration of specific postures adopted per day by housewives during each trimester at home and both at home and during working hours for those who were engaged in paid employment. Psychosocial stress was assessed using the Modified Life Events Inventory and the General Health Questionnaire 30. LBW was defined as a birthweight of less than 2500 g. Multiple logistic regression analysis was applied for controlling confounders and the results were expressed as adjusted odds ratios (OR) and 95% confidence intervals (95%CI).

RESULTS

Standing > 2.5 h/day (OR 2.26; 95%CI 1.10, 4.69) during the second trimester and sleeping 8 h or less/day (OR 2.84; 95%CI 1.49, 5.40) either during the second, third or both trimesters together, an increase in maternal age in years (OR 0.92; 95%CI 0.87, 0.98), and body mass index < 19.8 kg/m(2) (OR 2.2; 95%CI 1.17, 4.22) had a statistically significant association with LBW. Psychosocial stress was not associated with LBW.

CONCLUSIONS

Standing > 2.5 h/day and sleeping < or = 8 h/day were risk factors for LBW, whereas psychosocial stress was not.

Maternal age, education level and migration: socioeconomic determinants for smoking during pregnancy in a field study from Turkey

BACKGROUND

Smoking during pregnancy has been associated with socioeconomic determinants and it is recognized as the most important preventable risk factor for an unsuccessful pregnancy outcome. Turkey has national data on the prevalance of smoking during pregnancy; however there is no data on the characteristics of the high-risk population. This is a field study that aims to identify socioeconomic determinants for smoking during pregnancy as well as differentiating the daily and occasional smokers.

METHOD

Cross sectional study was conducted among women with 0-5 year old children living in the area served by Primary Health Care Center (PHCC) in Burhaniye, Turkey. Face-to-face interviews were conducted by the researchers during January-March 2008 at the home of the participants with 83.7% response rate (n = 256). The relation of "smoking during pregnacy" and "daily smoking during pregnancy" with the independent variables was determined with chi2 tests. Women's age, educational level, number of previous births, place of origin, migration, partner's educational level, poverty, perceived income, social class were evaluated. Statistical significance was achieved when the p value was less than 0.05. The variables in relation with the dependent variables in the chi2 tests were included in the forward-stepwise logistic analysis.

RESULTS

Prevalance of smoking during pregnancy was 22.7%. The majority (74.1%) were daily smokers. Young mothers (< 20), low educated women and migrants were at increased risk for smoking during pregnancy. Low education and being a migrant were risk factors for daily consumption (p < 0.05).

CONCLUSIONS

Systematic attention should be paid to socioeconomic determinants in smoking for pregnant women, especially in countries like Turkey with high rates of infant and mother mortality and substantial health inequalities. Young mothers (< 20), low educated women and migrants are important groups to focus on.

Association of maternal smoking status with breastfeeding practices: Missouri, 2005

OBJECTIVE

We sought to determine the association of smoking status as a risk factor for reduced initiation and duration of breastfeeding.

METHODS

The Missouri Pregnancy Related Assessment and Monitoring System collected a stratified sample of new mothers in 2005. Surveys were mailed, with telephone follow-up, and completed within 2 to 12 months after delivery. Respondents were classified as nonsmokers, smokers who quit during pregnancy, light smokers (<or=10 cigarettes per day), or moderate/heavy smokers (>10 cigarettes per day). Multivariable binomial regression and Cox proportional hazards models were used to assess breastfeeding initiation and duration according to smoking status.

RESULTS

Overall, 1789 women participated (weighted response rate: 61%). Approximately 74% of the women ever breastfed; 31% of the women ever smoked while pregnant. Compared with nonsmokers, the moderate/heavy smokers and light smokers were less likely to initiate breastfeeding, after controlling for sociodemographic characteristics, the presence of other smokers in the household, alcohol use, mode of delivery, and infant hospitalization. Compared with nonsmokers, the moderate/heavy smokers, light smokers, and smokers who quit during pregnancy were more likely to wean over time, controlling for the same covariates. There were no significant differences between nonsmokers and smokers regarding reasons for not initiating or ceasing breastfeeding.

CONCLUSIONS

Mothers who smoked initiated breastfeeding less often and weaned earlier than nonsmoking mothers. Incorporating knowledge of the association between smoking and breastfeeding into existing smoking-cessation and breastfeeding programs could provide opportunities to reduce perinatal exposure to tobacco smoke, improve interest in breastfeeding, and address other barriers to breastfeeding that smoking mothers may face.

Self-selection and bias in a large prospective pregnancy cohort in Norway

Self-selection in epidemiological studies may introduce selection bias and influence the validity of study results. To evaluate potential bias due to self-selection in a large prospective pregnancy cohort in Norway, the authors studied differences in prevalence estimates and association measures between study participants and all women giving birth in Norway. Women who agreed to participate in the Norwegian Mother and Child Cohort Study (43.5% of invited; n = 73 579) were compared with all women giving birth in Norway (n = 398 849) using data from the population-based Medical Birth Registry of Norway in 2000-2006. Bias in the prevalence of 23 exposure and outcome variables was measured as the ratio of relative frequencies, whereas bias in exposure-outcome associations of eight relationships was measured as the ratio of odds ratios. Statistically significant relative differences in prevalence estimates between the cohort participants and the total population were found for all variables, except for maternal epilepsy, chronic hypertension and pre-eclampsia. There was a strong under-representation of the youngest women (<25 years), those living alone, mothers with more than two previous births and with previous stillbirths (relative deviation 30-45%). In addition, smokers, women with stillbirths and neonatal death were markedly under-represented in the cohort (relative deviation 22-43%), while multivitamin and folic acid supplement users were over-represented (relative deviation 31-43%). Despite this, no statistically relative differences in association measures were found between participants and the total population regarding the eight exposure-outcome associations. Using data from the Medical Birth Registry of Norway, this study suggests that prevalence estimates of exposures and outcomes, but not estimates of exposure-outcome associations are biased due to self-selection in the Norwegian Mother and Child Cohort Study.

Prediction of birth weight by cotinine levels during pregnancy in a population of black smokers

OBJECTIVE

The goal was to investigate the association between maternal salivary cotinine levels (SCLs) and pregnancy outcomes among black smokers.

METHODS

In a randomized, controlled trial conducted in 2001-2004 in Washington, DC, 714 women (126 active smokers [18%]) were tested for SCLs at the time of recruitment and later in pregnancy. Sociodemographic health risks and pregnancy outcomes were recorded.

RESULTS

Birth weights were significantly lower for infants born to mothers with baseline SCLs of > or =20 ng/mL in comparison with <20 ng/mL (P = .024), > or =50 ng/mL in comparison with <50 ng/mL (P = .002), and > or =100 ng/mL in comparison with <100 ng/mL (P = .002), in bivariate analyses. In linear regression analyses adjusting for sociodemographic and medical factors, SCLs of > or =20 ng/mL were associated with a reduction in birth weight of 88 g when SCLs were measured at baseline (P = .042) and 205 g when SCLs were measured immediately before delivery (P < .001). Corresponding results were 129 g (P = .006) and 202 g (P < .001) for > or =50 ng/mL and 139 g (P = .007) and 205 g (P < .001) for > or =100 ng/mL. Gestational age was not affected significantly at any SCL, regardless of when SCLs were measured.

CONCLUSIONS

Elevated SCLs early in pregnancy or before delivery were associated with reductions in birth weight. At any cutoff level, birth weight reduction was more significant for the same SCL measured in late pregnancy. Maintaining lower levels of smoking for women who are unable to quit may be beneficial.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.

Calibrating self-reported measures of maternal smoking in pregnancy via bioassays using a Monte Carlo approach

Maternal smoking during pregnancy is a major public health problem that has been associated with numerous short- and long-term adverse health outcomes in offspring. However, characterizing smoking exposure during pregnancy precisely has been rather difficult: self-reported measures of smoking often suffer from recall bias, deliberate misreporting, and selective non-disclosure, while single bioassay measures of nicotine metabolites only reflect recent smoking history and cannot capture the fluctuating and complex patterns of varying exposure of the fetus. Recently, Dukic et al. have proposed a statistical method for combining information from both sources in order to increase the precision of the exposure measurement and power to detect more subtle effects of smoking. In this paper, we extend the Dukic et al. method to incorporate individual variation of the metabolic parameters (such as clearance rates) into the calibration model of smoking exposure during pregnancy. We apply the new method to the Family Health and Development Project (FHDP), a small convenience sample of 96 predominantly working class white pregnant women oversampled for smoking. We find that, on average, misreporters smoke 7.5 cigarettes more than what they report to smoke, with about one third underreporting by 1.5, one third under-reporting by about 6.5, and one third underreporting by 8.5 cigarettes. Partly due to the limited demographic heterogeneity in the FHDP sample, the results are similar to those obtained by the deterministic calibration model, whose adjustments were slightly lower (by 0.5 cigarettes on average). The new results are also, as expected, less sensitive to assumed values of cotinine half-life.

Birth weight among singletons born to foreign-born mothers in Taiwan: a population-based birth register study

BACKGROUND

We compared the birth weight of newborns born to foreign-born mothers (FBMs) and Taiwan-born mothers (TBMs), using data from the 2005-2006 Taiwan Birth Registry of singleton live births.

METHODS

The Wilcox-Russell method, data restriction, and multiple linear regression were used to analyze the data. The rates of low birth weight (<2500 g) with 95% confidence intervals were computed for TBMs, and for each of the nationalities of FBMs.

RESULTS

The mean birth weight of newborns of FBMs was 3157 g, which was higher than that of newborns of TBMs (3109 g). On analysis using the Wilcox-Russell method, both the rate and residual proportion of low-birth-weight (LBW) births were lower among newborns of FBMs (4.1% and 1.1%, respectively) than among newborns of TBMs (5.9% and 1.7%, respectively). After adjusting for sex, mode of delivery, maternal age, smoking status, predisposing maternal risk factors, and condition during pregnancy, the newborns of FBMs weighed 72.9 g (95% CI, 68.8 g to 77.0 g) more than the newborns of TBMs. When data were restricted to mothers without any adverse conditions and adjusted for maternal age, the differences in birth weight between the 2 groups remained unchanged. The rates of LBW deliveries among FBMs in Taiwan were significantly lower than those in their respective countries of origin.

CONCLUSIONS

In Taiwan, newborns of FBMs had a higher birth weight than those of TBMs, even after accounting for potential confounding factors, and had lower rates of LBW deliveries than did mothers in their respective countries of origin.

Alcohol consumption behavior of pregnant women in Japan

OBJECTIVE

This study was conducted to clarify the prevalence of alcohol consumption among pregnant women in Japan and its associated factors.

METHOD

344 institutions participated in the survey which was conducted in February 2006. Each subject was requested to fill out a self-administered anonymous questionnaire. Factors associated with alcohol consumption during pregnancy were examined using the chi-squared test and logistic regression analysis.

RESULTS

The number of effective responses was 18,965. The prevalence of alcohol consumption before the confirmation of pregnancy and during pregnancy was 44.6% and 4.6% respectively. The following items were recognized as being associated with promoting alcohol consumption during pregnancy: greater number of weeks of pregnancy, more pregnancies, fewer years of schooling, being employed, an alcohol consumption before the confirmation of pregnancy, smoking during pregnancy, ignorance about the effects of alcohol consumption on fetuses, receiving advice regarding alcohol abstention, difficulty maintaining sleep, and daytime sleepiness.

CONCLUSION

It is important to have a more comprehensive understanding of the factors associated with the alcohol consumption behavior of pregnant women, as revealed in the present study, in order to develop future policies for preventing alcohol consumption among pregnant women.

Association of smoking during pregnancy and fetal growth restriction: subgroups of higher susceptibility

OBJECTIVE

To analyze the association between maternal smoking and fetal growth restriction, defined as a failure to achieve the growth potential, and to define subgroups of higher susceptibility for this association.

STUDY DESIGN

A definition of growth restriction by customized birthweight standards applied to 13,661 non-malformed singleton deliveries. Customization was performed by maternal ethnic origin, height, booking weight, parity, gestational age at delivery and fetal gender. The adjusted risk of smoking for customized smallness-for-gestational age and the identification of subgroups with higher susceptibility were assessed by logistic regression.

RESULTS

Overall, the adjusted odds ratio of smoking (all levels of exposure grouped) for the occurrence of growth restriction was 1.9 (95% confidence interval: 1.69-2.13). Smoking was etiologically responsible for 13.9% (95% confidence interval: 11.2-16.5) of the cases of growth restriction occurring in the population. Smoking resulted in an increasingly greater risk of growth restriction with progressive levels of cigarette consumption. The risk of smoking for fetal growth restriction was significantly greater in older women and those with a previous history of spontaneous preterm delivery.

CONCLUSIONS

Smoking is associated with a higher risk for growth restriction. In addition, older pregnant women and those with a previous history of preterm delivery have an increased susceptibility.

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.

Pre-Conception Practices Among FamilyPhysicians and Obstetrician-Gynaecologists:Results from a National Survey

OBJECTIVE

To determine the pre-conception practices among obstetrician-gynaecologists and family physicians in Canada.

METHODS

Between October 2001 and May 2002, a survey was mailed to a national random sample of obstetricians and gynaecologists (n = 539) and family physicians (n = 2378) who were current members of the College of Family Physicians of Canada or the Society of Obstetricians and Gynaecologists of Canada.

RESULTS

Response rates were 41.7% among obstetrician-gynaecologists and 31.1% among family physicians. More than 85% of physicians frequently discussed birth control and Pap testing with women of childbearing age, but fewer than 60% frequently obtained a detailed history of alcohol use. Fewer than 50% of physicians frequently discussed the following with women of childbearing age: weight management, workplace stress, mental health, addiction history, or the risks of substance use during pregnancy. Fewer than 15% enquired about a history of sexual or emotional abuse. Family physicians were significantly more likely than obstetrician-gynaecologists to discuss mental health (41.1% vs. 28.1%), depression (44.5% vs. 29.0%), and history of alcohol use (59.8% vs. 47.9%) with women of childbearing age (all P < 0.05). Obstetrician-gynaecologists were significantly more likely than family physicians to discuss folic acid (57.8% vs. 47.2%), sexual abuse (18.2% vs. 10.8%), smoking (56.0% vs. 46.1%), and drug use (45.8% vs. 35.9%) (all P < 0.05) with women of childbearing age who were not pregnant.

CONCLUSION

There are missed opportunities in pre-conception screening to identify women with suboptimal reproductive health status who are at risk for adverse conception, pregnancy, and birth outcomes. Physician training in identification of women at risk would allow for increased primary and secondary prevention efforts through referral to appropriate treatment and resources.

Relation of Maternal Low Birth Weight to Infant Growth Retardation and Prematurity

OBJECTIVES

This study sought to determine the relationship between maternal birth weight, infant intrauterine growth retardation, and prematurity.

METHODS

Stratified and logistic regression analyses were performed on a dataset of computerized Illinois vital records of African American (N = 61,849) and White (N = 203,698) infants born between 1989 and 1991 and their mothers born between 1956 and 1975.

RESULTS

Race-specific rates of small-for-gestational age (weight-for-gestational age <10th percentile) and preterm (<37 weeks) infants rose as maternal birth weight declined. The adjusted (controlling for maternal age, education, marital status, parity, prenatal care utilization, and cigarette smoking) odds ratio (95% confidence interval) of small-for-gestational age for maternal low birth weight (<2,500 g) among African Americans and Whites were 1.7 (1.1.4-1.9) and 1.8 (1.7-2.0), respectively. The adjusted odds ratio (95% confidence interval) of prematurity for maternal low birth weight (<2,500 g) among African Americans and Whites were 1.6 (1.3-1.9) and 1.3 (1.0-1.6), respectively. The racial disparity in the rates of small-for-gestational age and prematurity persisted independent of maternal birth weight: adjusted odds ratio equaled 2.2 (2.1-2.4) and 1.5 (1.4-1.7), respectively.

CONCLUSIONS

Maternal low birth weight is a risk factor for infant intrauterine growth retardation and prematurity among African Americans independent of maternal risk status during pregnancy; it is a risk factor for infant intrauterine growth retardation among Whites. Maternal low birth weight fails to explain the racial disparity in the rates of small-for-gestational age and premature infants.

Maternal smoking and birth weight: interaction with parity and mother's own in utero exposure to smoking

BACKGROUND

Few studies have reported interactions between maternal smoking and other maternal characteristics and exposures. We examined maternal smoking in a cohort study for which data from 3 generations were available to examine maternal characteristics and exposures from a life-course perspective.

METHODS

We had data from 3 generations: women enrolled in the U.S. Collaborative Perinatal Project (CPP) between 1959 and 1965 at the Baltimore site (G1); daughters (G2) of those G1 mothers who were followed to ages 27-33 years in the Pathways to Adulthood study; and children (G3) born to the G2 women who provided pregnancy and birth information during the Pathways study. These data allowed examination of exposures that occurred to the mother during her childhood and in utero.

RESULTS

We found evidence of a 3-way interaction effect on birth weight for maternal smoking in pregnancy, maternal exposure to smoking in utero (grandmaternal smoking), and maternal parity. Maternal smoking reduced birth weight in 3 of the subgroups, with the size of the effect on birth weight moderated by parity and the mother's own in utero exposure to smoking.

CONCLUSIONS

A mother's prenatal exposure to smoke may affect the birth weight of her offspring. This effect would be consistent with both the accumulation-of-risk and the fetal-programming hypotheses.

Smoking-associated fetal morbidity among older gravidas: a population study

BACKGROUND

We set out to assess the influence of advanced maternal age on fetal morbidity associated with smoking during pregnancy in a population-based retrospective study of 7 792 990 singleton live births between 1995 and 1997 in the United States with documented maternal smoking habit.

METHODS

The study group consisted of infants born to mothers aged>or=40 years (older mothers). Two maternal age categories (20-29, "younger mothers"; 30-39, "mature mothers") were constructed as comparison groups. Adjusted odds ratios (ORs) generated from logistic regression models were used to compare fetal morbidity indices associated with smoking across maternal age categories. Main outcome measures included preterm, very preterm, and small for gestational age (SGA).

RESULTS

The prevalence of smoking was 13.1%, and decreased with increasing maternal age. Regardless of maternal age, the risk for fetal morbidity was significantly elevated if the mother smoked. The risks for preterm and SGA associated with smoking were significantly higher among older gravidas as compared to younger mothers while mature mothers had risk estimates comparable to those of older mothers. Among smoking mothers only, the risk pattern for fetal morbidity was J-shaped, with babies of older smokers having significantly higher fetal morbidity indices, while those of mature smokers showed lower levels of risk as compared to younger mothers.

CONCLUSION

In an era of relatively lower prevalence of smoking during pregnancy, advanced maternal age still increases the risk of smoking-associated fetal morbidity. Our findings reveal new information of elevated risk for very preterm births among older smoking mothers.

Low birth weight across generations

OBJECTIVES

This study sought to determine the relationship between maternal birth weight, prenatal care usage, and infant birth weight.

METHODS

Stratified and logistic regression analyses were performed on a dataset of computerized Illinois vital records of White (N = 187, 074) and African-American (N = 58,856) infants born between 1989 and 1991 and their mothers born between 1956 and 1975.

RESULTS

Among White mothers who received adequate prenatal care, the low birth weight (<2500 g) rate was 4% for infants of former low birth weight mothers (N = 5230) compared to 2.1% for infants of former nonlow birth weight mothers (N = 93,011), relative risk equaled 1.9(1.7-2.2); the population attributable risk of maternal low birth weight was 4.1%. Among African American mothers who received adequate prenatal care, the low birth weight rate was 15% for infants of former low birth weight mothers (N = 2196) compared to 7.2% for infants of former nonlow birth weight mothers (N = 14,607), relative risk equaled 2.1(1.9-2.4); the population attributable risk of maternal low birth weight was 10.9%. The maternal-infant birth weight associations were consistent across all maternal age, education, marital status, and prenatal care categories.

CONCLUSIONS

Maternal low birth weight is a risk factor for infant low birth weight independent of risk status during the current pregnancy. A greater percentage of low birth weight African American (compared to White) infants are attributable to maternal low birth weight.

Fetal Alcohol and Drug Effects

BACKGROUND

Alcohol and drug use by pregnant women are harmful to the developing embryo and fetus. Teasing apart the specific contributions of each substance to adverse child outcome, however, proves difficult in practice. The risks to the neonate include intra-uterine growth retardation, birth defects, altered neurobehavior, and withdrawal symptoms. Subsequent behavior, development, and neurologic function may also be impaired.

REVIEW SUMMARY

Maternal cigarette smoking carries the greatest risk of impaired fetal growth of any of the substances discussed herein and has been linked to subsequent externalizing behaviors. Alcohol is a well-established teratogen. Heavy exposure to alcohol in a subset of infants is associated with fetal alcohol syndrome (FAS). Mental retardation is one of the main sequelae of alcohol exposure in utero. Fetal marijuana exposure has no consistent effect on outcome. Prenatal cocaine exposure has not been shown to have any detrimental effect on cognition, except as mediated through cocaine effects on head size. Although fetal cocaine exposure has been linked to numerous abnormalities in arousal, attention, and neurologic and neurophysiological function, most such effects appear to be self-limited and restricted to early infancy and childhood. Opiate exposure elicits a well-described withdrawal syndrome affecting central nervous, autonomic, and gastrointestinal systems, which is most severe among methadone-exposed infants.

CONCLUSION

Most adverse effects of prenatal drug exposure are self-limited, with catch-up growth and resolution of withdrawal and of prior neurobehavioral abnormalities noted over time. The exception is alcohol, which is linked to life-long impairments (i.e., mental retardation and microcephaly) and possibly cigarette-related behavioral effects. The absence of tangible evidence of detrimental long-term cocaine effects may reflect limitations in the methodology used to identify children at greatest risk for adverse outcome.

The effects of smoking on birthweight-for-gestational-age curves in teenage and adult primigravidae

OBJECTIVE

To compare the effect of smoking on the birthweight-for-gestational-age curves of teenage and adult primigravidae.

METHODS

A retrospective analysis of the perinatal database at the Liverpool Women's Hospital for the years 1997-1999 for teenage and adult primigravidae.

RESULTS

Records on 1157 primigravidae were available. There were no significant differences between the mean birthweight (3220 g +/- 666 vs 3244 g +/- 680, P = 0.43) and the proportion with low birthweight (LBW) babies (8.9% vs 10.6%, P = 0.39) between teenage and adult primigravidae, respectively. The percentage of women who smoked increased from the middle class (Townsend score -6- - 3) to the working class group (Townsend score +4- + 12) for both teenagers (33.3-51.3%) and adults (6.9-29.6%). The mean birthweight of babies of smoking mothers was significantly lower than for non-smoking mothers (3112 g +/- 639 vs 3327 g +/- 663, P = 0.00002). The birthweight-for-gestational-age pattern was lower at all gestational ages for smoking mothers in both the teenage and adult groups. Risk of LBW was significantly increased in teenagers who smoked (10.8% vs 3.9%, P < 0.01), but not in adult smokers.

CONCLUSION

Lower birthweights at all gestational ages were observed in babies of teenage and adult mothers who smoked.

Epidemiology of preterm deliveries in Southeast Brazil: a hospital-based study

OBJECTIVES: to evaluate the role of some factors in the genesis of preterm deliveries in Southeast Brazil. METHODS: a cohort hospital-based study of 589 mothers who delivered in Taubaté, a middle-size city in the state of São Paulo, Brazil, between May 1, and October 31, 1999. The statistical approach was Risk Ratio with statistical significance established at alpha: 5%. RESULTS: 70 preterm newborns were identified representing 11,9% of the total birth rate. The variables holding statistical significance were: previous history of stillbirth delivery, smoking during pregnancy, poor weight gain, arterial hypertension, vaginal bleeding, genitourinary tract infection and five or less medical visits for prenatal care. CONCLUSIONS: this study indicates that good quality prenatal care has a great value in preventing preterm births, for poor weight gain, arterial hypertension, vaginal bleeding, genitourinary tract infection and smoking are conditions that can be controlled in the course of pregnancy.

Effect of maternal age, smoking and deprivation on birthweight

Low birthweight is often used as a health indicator. This paper reports the findings of a cohort study, which were analysed to determine the relationship, if any, between the age of the mother and birthweight given the mother's smoking habits and the level of social deprivation of the mother's place of residence. The data used were extracted from those data routinely collected by the Information and Statistics Division of the National Health Service, Scotland. Information on 178,801 singleton live births occurring between 1992 and 1994 was used in the analysis. The factors considered were those available directly from the official records. The level of social deprivation was measured using Carstairs index based on the postcode sector. Although younger and older mothers have lighter babies, on average, it was found that this effect can be largely explained by differences in the smoking habits and level of deprivation of the mothers. Birthweight, adjusted for gestational age, sex of the baby and parity of the mother, was significantly lower for babies born to mothers who smoked during pregnancy. It is clear, however, that the detrimental effect of smoking increases with the age of the mother. Although adjusted birthweight was lower for those in areas of high deprivation, this effect is small compared with the effect of smoking. Any attempt to decrease the percentage of low-birthweight babies must focus on reducing the percentage of mothers who smoke.

Prenatal active or passive tobacco smoke exposure and the risk of preterm delivery or low birth weight

We examined the association of exposure to environmental tobacco smoke with birth weight and gestational age in a large, prospective study. We also compared these endpoints between infants of active maternal smokers and those of non-smoking, non-ETS exposed women. Pregnant women were interviewed by telephone during the first trimester, and pregnancy outcome was determined for 99%. Among the 4,454 singleton live births that could be linked to their birth certificate, we confirmed increased risks of low birth weight and small for gestational age with heavier maternal smoking (> 10 cigarettes/day), as well as noting an increased risk for "very preterm" birth (< 35 weeks). These associations were generally stronger among infants of older (> or = 30 years) than those of younger mothers, as well as among non-whites. High environmental tobacco smoke exposure (> or = 7 hours/day in non-smokers) was moderately associated with low birth weight (adjusted odds ratio (AOR) 1.8, 95% confidence limits (95% CL) = 0.82, 4.1), preterm birth (AOR 1.6, 95% CL = 0.87, 2.9), and most strongly with very preterm birth (AOR 2.4, 95% CL = 1.0, 5.3). These associations were generally greater among non-whites than whites. The data support earlier studies suggesting that prenatal environmental tobacco smoke exposure, in addition to maternal smoking, affects infant health.

Does smoking by pregnant women influence IQ, birth weight, and developmental disabilities in their infants? A methodological review and multivariate analysis

Neuropsychologists are asked frequently to address the issue of the cause of a variety of central nervous system problems that may affect higher cortical function. One such issue is the relationship of maternal smoking to adverse reproductive outcomes involving neocortical insult including mental retardation, learning disabilities, attention-deficit hyperactivity disorder, and other insults that may be related to prolonged hypoxic states in utero. The instant paper develops the issue of causation as a scientific inquiry, reviews several traditional, applicable models, and critiques these models. An additional model of motility is proposed and discussed. The issue of the relationship of maternal smoking to adverse reproductive outcomes is then addressed from a review perspective along with new empirical analyses, the latter demonstrating that researchers tend to draw causal conclusions independent of whether the respective design of their studies would support conclusions about the causation of an event. Causal conclusions in the absence of causal designs have often lead to incomplete and incorrect conclusions. It is necessary to match conclusions not only to the outcomes of a research project but also to its design and accompanying limitations.

Growth from birth to early adolescence in offspring prenatally exposed to cigarettes and marijuana

Weight, height, and head circumference were examined in children from birth to early adolescence for whom prenatal exposure to marijuana and cigarettes had been ascertained. The subjects were from a low-risk, predominantly middle-class sample participating in an ongoing longitudinal study. The negative association between growth measures at birth and prenatal cigarette exposure was overcome, sooner in males than females, within the first few years, and by the age of six, the children of heavy smokers were heavier than control subjects. Pre and postnatal environmental tobacco smoke did not have a negative effect upon the growth parameters; however, the choice of bottle-feeding or shorter duration of breast-feeding by women who smoked during pregnancy appeared to play an important positive role in the catch-up observed among the infants of smokers. Prenatal exposure to marijuana was not significantly related to any growth measures at birth, although a smaller head circumference observed at all ages reached statistical significance among the early adolescents born to the heavy marijuana users.

Adverse pregnancy outcome in schizophrenic women: occurrence and risk factors

Low birth weight and preterm birth are important predictors of infant mortality and morbidity, and may increase the risk of schizophrenia. These adverse outcomes of pregnancy could be associated, therefore, with increased risk in children genetically predisposed to schizophrenia. The aim of this review was to describe the occurrence of risk factors for low birth weight, preterm birth, and perinatal death among schizophrenic women, and to describe the incidence of those adverse pregnancy outcomes among schizophrenic women. Smoking, substance abuse, and low socioeconomic status are associated with fetal growth retardation, preterm birth, and perinatal death, and also with schizophrenia. Therefore, increased incidence of adverse pregnancy outcome should be expected in schizophrenic women. The available evidence suggests that schizophrenic women are at increased risk of delivering infants with low birth weight, but the existing studies are of small statistical power. Preterm birth and perinatal death have only been investigated little among schizophrenic women. An important focus of future research should be to establish the risk of adverse pregnancy outcome, and to study the association between the suspected risk factors and pregnancy outcome in schizophrenic women. In clinical work with pregnant schizophrenic women, efforts should be made to prevent exposure to suspected risk factors like smoking, substance use, and socioeconomic problems. This could possibly decrease the mortality and morbidity, including the risk of schizophrenia in the offspring, and clarify the importance of environmental and genetic factors in the etiology of schizophrenia.

[Smoking behavior of pregnant patients and mothers with young children]

The aim of the study is to analyse the smoking behaviour of pregnant women and mothers with young children and to identify sociodemographic factors for the nicotine consumption of these persons. Data basis are the national and regional health examination surveys of the German Cardiovascular Prevention Study (GCP). Included were 8385 females in the age group 25-40 years. 326 (3.9%) of these females were pregnant at the time of the survey, and 2538 (30.3%) were mothers with one or more children, aged up to 5 years. Smoking behaviour, family status, number and age of the children and other sociodemographic variables were determined with a self-administered standardised questionnaire. Altogether, 39.4% of the 8385 females reported that they were current smokers. The prevalence of smoking for females without young children was slightly higher (42.3%). 20.6% of all pregnant females were current smokers. For mothers in the lowest social class, the smoking prevalence was two times higher compared to mothers in the highest social class. Unmarried and divorced mothers yielded a very high smoking prevalence. These results suggest that there is a need for prevention and health promotion programs for pregnant females and young mothers. Special emphasis should be targetted at unmarried young mothers and mothers from socially disadvantaged population groups.

Umbilical cord plasma erythropoietin levels in pregnancies complicated by maternal smoking

OBJECTIVE

Our goal was to determine whether maternal smoking was associated with elevated umbilical cord erythropoietin, a marker for chronic hypoxia.

STUDY DESIGN

Plasma erythropoietin levels were measured in umbilical cord plasma of 222 newborns. There were 48 mothers who smoked and 174 nonsmokers.

RESULTS

When all pregnancies were included, mean cord plasma erythropoietin levels were significantly higher in the smokers (78.0 +/- 15.3 mIU/ml) compared with the nonsmoking group (35.2 +/- 4.0 mIU/ml; p < 0.005). Regression analysis showed a significant positive correlation between the number of cigarettes smoked per day and cord plasma erythropoietin levels (r = 0.26, p < 0.0001). Smoking was associated with a significantly elevated risk (relative risk = 2.6, 95% confidence interval 1.7 to 10.9, p < 0.005) of fetal growth restriction. When pregnancies with fetal growth restriction were excluded from the analysis, the difference between the two groups remained significant (smokers 81.3 +/- 18.6, n = 38; nonsmokers 24.3 +/- 1.4, n = 164; p < 0.03).

CONCLUSIONS

These results illustrate that smoking during pregnancy is associated with fetal growth restriction and significantly elevated umbilical cord erythropoietin levels.

Differing birth weight among infants of U.S.-born blacks, African-born blacks, and U.S.-born whites

BACKGROUND

In the United States, the birth weights of infants of black women are lower than those of infants of white women. The extent to which the lower birth weights among blacks are related to social or genetic factors is unclear.

METHODS

We used vital records for 1980 through 1995 from Illinois to determine the distribution of birth weights among infants born to three groups of women -- U.S.-born blacks, African-born blacks, and U.S.-born whites.

RESULTS

The mean birth weight of 44,046 infants of U.S.-born white women was 3446 g, that of 3135 infants of African-born black women was 3333 g, and that of 43,322 infants of U.S.-born black women was 3089 g. The incidence of low birth weight (weight less than 2500 g) was 13.2 percent among infants of U.S.-born black women and 7.1 percent among infants of African-born black women, as compared with 4.3 percent among infants of U.S.-born white women (relative risks, 3.1 and 1.6, respectively). Among the women at lowest risk (those 20 to 39 years old, with 12 years of education for themselves and their spouses, early prenatal care, gravida 2 or 3, and no previous fetal loss), the rate of low birth weight in infants of African-born black women (3.6 percent) was closer to the rate in infants of U.S.-born white women (2.4 percent), and the rate in infants of U.S.-born black women remained high (7.5 percent).

CONCLUSIONS

The birth-weight patterns of infants of African-born black women and U.S.-born white women are more closely related to one another than to the birth weights of infants of U.S.-born black women.

Assessing the impact of adolescent pregnancy and the premarital conception stress complex on birth weight among young mothers in Gibraltar's civilian community

PURPOSE

The objective of this study was to assess the impact of young maternal age and the timing of conception on birth weight among primiparous women living in Gibraltar.

METHODS

The data for this study were derived from a population of 295 primiparous women who gave birth under 25 years of age. Only married women who had no previous maternal history and delivered live singleton newborns between 1980 and 1984 were included. The confounding effects of gestation length, sex, and socio-economic status on birth weight were taken into account using the multivariate technique of multiple classification analysis. A conception timing variable was constructed and partitioned into four groups which represented the separate and joint effects of maternal age and prenuptial stress on birth weight.

RESULTS

The overall mean birth weight was 3344.15 g. After controlling for the specified factors and covariate, the infants of older mother (> 19) who conceived after marriage weighed 57.78 g above the referent group mean. Older mothers who conceived a child before marriage delivered infants weighing 75.67 below the grand mean. Young mother (< 20) who conceived within marriage had infants who weighed 37.32 g less than the grand mean. Infants delivered by young mothers who conceived before marriage weighed 133.66 g less than the overall mean birth weight. The only significant group difference detected within the conception timing variable was between young mothers who conceived before marriage versus older mothers who conceived after marriage.

CONCLUSIONS

Premarital conception is identified as a risk factor for lower infant birth weights among mothers under 20 years of age. This study emphasizes the need to take into account the effects of culturally mediated behavior on the pregnancy experience of young women.

The effect of maternal smoking on birth weight in twin pregnancies

Information on 869 076 singletons and 17 566 twins, born during the period 1983-1991, was obtained from the Swedish Medical Birth Registry. Data on birth weight, gestational duration, vital status, and maternal smoking habits during pregnancy were analyzed in order to investigate whether twinning potentiates the effect of maternal smoking on birth weight and perinatal mortality. The individual birth weights were expressed as percentages of mean birth weight, where mean birth weights of singletons and twins were calculated separately. The birth weight reducing effect of maternal smoking was found to be of the same magnitude among twins and singletons weighing > 90% of mean birth weight. For infants weighing < 90% of mean birth weight, maternal smoking had a significantly stronger effect on birth weight among singletons than among twins. When gestational duration was taken into consideration, this difference was less pronounced. The effect of maternal smoking on gestational duration was stronger among singletons than twins. The smoking-related risk increase of perinatal death was of about the same magnitude among twins and singletons.

Low birthweight in a public prenatal care program: behavioral and psychosocial risk factors and psychosocial intervention

A retrospective, observational study of 3073 low income African American, Latina, and White women receiving comprehensive prenatal care at 26 provider sites was completed. The purpose of the study was to test three hypotheses. First, after adjustment for biomedical complications, the presence of maternal behavioral and psychosocial factors would be associated with an increased rate of low birthweight infants. Second, increased time spent in psychosocial services would negate the relationship between maternal psychosocial factors and low birthweight. Third, after adjusting for biomedical, behavioral, and psychosocial factors, rates of low birthweight would no longer differ by race. Maternal smoking (over five cigarettes per week), maternal low weight for height and/or weight gain, negative mood (depression, anxiety, and/or hostility) and rejection of the pregnancy were found to be related to an increased rate of low birthweight birth (< 2500 g). Receiving more than 45 min of psychosocial services was related to a reduced rate of low birthweight birth for all women regardless of risk profile. The rate of low birthweight remained higher in African American women after adjusting for all significant maternal biomedical, behavioral, and psychosocial risk and intervention factors. Further analyses revealed that the strength and direction of the relationship between time spent in psychosocial services and low birthweight remained after controlling for the number of prenatal care visits, the time spent in nutrition or health educational services, and gestational age. Also, the time spent in psychosocial services was related to a reduced rate of low birthweight even after excluding time spent in psychosocial services in the third trimester of pregnancy or excluding women who received their first psychosocial assessment in the third trimester from the analysis. Although definitive evidence from randomized trials of psychosocial services is lacking, receiving over 45 min of psychosocial services was related to a reduced risk of low birthweight for all women in this study. Therefore, general psychosocial services appears to be an important component of prenatal care for all low income women.

Parental cigarette smoking and risk for congenital anomalies of the heart, neural tube, or limb

Risks for selected congenital anomalies from parental smoking were investigated in a case-control study in California. Mothers of 207 infants with conotruncal heart defects, 264 infants with neural tube defects, 178 infants with limb deficiencies, and 481 live born control infants delivered in 1987-1988 were interviewed by telephone. Modestly elevated risks were observed for conotruncal heart defects and limb deficiencies, associated primarily with both parents smoking. An odds ratio of 1.9 (95 percent confidence interval 1.2-3.1) was observed for conotruncal heart defects and an odds ratio of 1.7 (95% confidence interval 0.96-2.9) for limb deficiencies when both parents smoked compared to neither parent smoking. We did not observe increased risks associated with maternal smoking in the absence of paternal smoking, although an increased risk associated with paternal smoking in the absence of maternal smoking was observed for limb deficiencies in offspring. For conotruncal defects, the risks associated with parental smoking differed among race/ethnic groups. Parental smoking was not associated with increased risks for neural tube defects. Observed risks did not change substantially when adjusted for maternal vitamin use, alcohol use, and gravidity. Some heterogeneity in risk was observed for phenotypic case subgroups, but data were too sparse to draw firm inferences.