Low birthweight, preterm births and intrauterine growth retardation in relation to maternal smoking

The association between the intensity and duration of cigarette smoking during pregnancy and the frequency of low birthweight, preterm births and intrauterine growth retardation was investigated in a historical cohort. All 5166 livebirths occurring in the city of Pelotas, Brazil, during 1993 were identified and mothers interviewed soon after delivery. Children whose mothers smoked during pregnancy had a birthweight 142 g lower than those of non-smoking mothers. The odds ratio for low birthweight among children of smokers was 1.59 [95% CI 1.30–1.95]. There was no association between smoking and preterm delivery assessed by the Dubowitz score. In relation to intrauterine growth retardation, smoking was associated with an odds ratio of 2.07 [95% CI 1.69–2.53]. There was a direct dose–response association between the number of cigarettes smoked and the risk of growth retardation. Women whose partner smoked were also at higher risk of having a child with growth retardation. All the above results were adjusted for confounding factors. The effect of maternal smoking on low birthweight seems to be attributable to intrauterine growth retardation rather than preterm delivery.     

Adverse perinatal and neonatal outcomes and their determinants in rural Vietnam 1999-2005

Population-based estimations of perinatal and neonatal outcomes are sparse in Vietnam. There are no previously published data on small for gestational age (SGA) infants. A rural population in northern Vietnam was investigated from 1999 to 2005 (n=5521). Based on the birthweight distributions within the population under study, reference curves for intrauterine growth for Vietnamese infants were constructed and the prevalence and distribution of SGA was calculated for each sex. Neonatal mortality was estimated as 11.6 per 1000 live births and the perinatal mortality as 25.0 per 1000 births during the study period. The mean birthweight was 3112 g and the prevalence of low birthweight was 5.0%. The overall prevalence of SGA was 6.4%. SGA increased with gestational age and was 2.2%, 4.5% and 27.1% for preterm, term and post-term infants, respectively. Risk factors for SGA were post-term birth: adjusted odds ratio (AOR) 7.75 [95% CI 6.02, 9.98], mothers in farming occupations AOR 1.72 [95% CI 1.21, 2.45] and female infant AOR 1.61 [95% CI 1.27, 2.03]. There was a pronounced decrease in neonatal mortality after 33 weeks of gestation. Suggested interventions are improved prenatal identification of SGA infants by ultrasound investigation for fetal growth among infants who do not follow their expected clinical growth curve at the antenatal clinic. Other suggestions include allocating a higher proportion of preterm deliveries to health facilities with surgical capacity and neonatal care.     

Fetal growth, maternal prenatal smoking, and risk of invasive meningococcal disease: a nationwide case-control study

BACKGROUND: The prenatal period may be important for susceptibility to infections. We evaluated whether low birthweight, prematurity, and prenatal maternal smoking were associated with increased risk of invasive meningococcal disease. METHODS: We linked the Danish nationwide National Registry of Patients, the Birth Registry, and social registries to obtain data on fetal growth and social factors on 1921 cases of meningococcal disease hospitalized between 1 January, 1980 and 31 December, 1999 (median age 31 months, interquartiles 13-65 months) and 37 451 population controls. The impact of maternal smoking was examined in a subsample of 462 cases and 9240 controls born after 1990, when data on smoking became available in the Birth Registry. RESULTS: The adjusted odds ratios (OR) of meningococcal disease associated with low birthweight (<2500 g) varied between 1.6 (95% CI: 1.1, 2.3) in infants <12 months to 1.5 (95% CI: 1.0, 2.3) in children >60 months of age at hospitalization for meningococcal disease. Premature children had an increased risk of meningococcal disease during the first year of life only (adjusted OR = 1.3, 95% CI: 1.1, 1.9). The effect of low birthweight was very similar among mature and premature children. The adjusted OR for maternal smoking was 1.8 (95% CI: 1.4, 2.2). CONCLUSIONS: Low birthweight is associated with an increased risk of meningococcal disease throughout childhood, while an effect of prematurity persists only for 12 months. Maternal prenatal smoking was associated with the risk of meningococcal disease.     

The influence of maternal cigarette smoking, snuff use and passive smoking on pregnancy outcomes: the Birth To Ten Study

This article describes the patterns and effects of maternal snuff use, cigarette smoking and exposure to environmental tobacco smoke during pregnancy on birthweight and gestational age, in women living in Johannesburg and Soweto in 1990. A cohort of 1593 women with singleton live births provided information about their own and household members' usage of tobacco products during pregnancy. The women completed a questionnaire while attending antenatal services. Data on gestational age and birthweight were obtained from birth records. Women who smoked cigarettes or used snuff during pregnancy accounted for 6.1% and 7.5% of the study population respectively. The mean birthweight of non-tobacco users was 3148 g [95% CI 3123, 3173] and that of the smokers 2982 g [95% CI 2875, 3090], resulting in a significantly lower mean birthweight of 165 g for babies of smoking mothers (P = 0.005). In contrast, women using snuff gave birth to infants with a mean birthweight of 3118 g [95% CI 3043, 3192], which is a non-significant (P = 0.52) decrease (29.4 g) in their infants' birthweights compared with those not using tobacco. A linear regression analysis identified short gestational age, female infant, a mother without hypertension during pregnancy, coloured (mixed racial ancestry), and Asian infants compared with black infants, lower parity, less than 12 years of education and smoking cigarettes as significant predictors of low birthweight, while the use of snuff during pregnancy was not associated with low birthweight. The snuff users, however, had a significant shorter gestational age than the other two groups of women. The birthweight reduction adjusted for possible confounders was 137 g [95% CI 26.6, 247.3 (P = 0.015)] for cigarette smokers and 17.1 g [95% CI -69.5, -102.7, P = 0.69] for snuff users respectively, compared with the birthweight of non-tobacco users. Among women who did not smoke cigarettes or use snuff, exposure to environmental tobacco smoke did not result in significant effects on the birthweight of their infants. In conclusion, infants of cigarette smokers had significantly lower birthweights than those of non-tobacco users or snuff users who are exposed to nicotine during pregnancy. Passive smoking did not affect birthweight significantly in this population.     

Caffeine consumption during pregnancy and fetal growth.

BACKGROUND: The purpose of this study was to examine the association between maternal caffeine consumption and low birthweight, intrauterine growth retardation, and prematurity, adjusting for multiple confounders. METHODS: Data obtained from birth certificates and interviews on 1,230 women with singleton live births were analyzed to evaluate the potential influence of caffeine consumption during the first trimester on fetal growth. RESULTS: The crude odds ratio for intrauterine growth retardation in infants of women reporting heavy caffeine consumption (greater than 300 mg/day) was 3.86 (95% CI = 1.80, 8.40) which decreased to 2.90 (95% CI = 1.23, 6.87) after controlling for confounding factors. The adjusted odds ratio for low birthweight and heavy maternal caffeine consumption was also elevated (OR = 2.05; 95% CI = 0.86, 4.88). Women who reduced their caffeine intake from greater than 300 mg/day to less than that early in pregnancy had lower risks of delivering infants with either intrauterine growth retardation or low birthweight than women who continued to consume that amount. Preterm delivery appeared to be unrelated to caffeine consumption. CONCLUSIONS: Taken together with studies reporting similar findings, these results suggest that heavy caffeine consumption increases the risk for fetal growth retardation.     

Intrauterine growth retardation and premature delivery: the influence of maternal smoking and psychosocial factors.

OBJECTIVES. This study investigated the influence of psychosocial stress, maternal schooling, social support, psychological well-being, alcohol, and smoking on intrauterine growth retardation and premature delivery. METHODS. At a Copenhagen university hospital, 2432 pregnant women completed a questionnaire on general health, psychosocial stressors, and sociodemographic characteristics. RESULTS. In 212 cases (8.7%) the women delivered prematurely. Preterm delivery as associated with psychosocial stress (adjusted odds ratio [OR]=1.14 for each 1-point increase on the psychosocial stressor 5-point scale and 1.92 for the whole scale) and poor school education (adjusted OR=2.62 for 7-9 years of schooling, 1.91 for 10 years, and 1.0 for 11-13 years). In 152 cases (6.3%), infants had a birthweight below the 10th percentile. Intrauterine growth retardation was associated with smoking, daily drinking, school education, and social network variables. In a multiple logistic regression model, intrauterine growth retardation was associated with smoking habits (adjusted OR=2.40 for 0-9 cigarettes daily, 2.68 for 10-15 daily, and 2.88 for more than 15 daily). CONCLUSIONS. Psychosocial stressors and limited duration of schooling appeared to influence preterm delivery. Smoking habits influenced intrauterine growth retardation.     

Determinants of developmental delay in infants aged 12 months

The aim of this study was to determine which demographic, maternal, obstetric and postnatal variables were associated with achievement of developmental milestones at the age of 12 months in term infants. Mothers and babies were enrolled in the Auckland Birthweight Collaborative Study shortly after birth. All infants were full term (gestation >or= 37 weeks). Approximately half of the sample were small for gestational age (SGA = birthweight 10th percentile). A maternal interview was conducted soon after birth. Phase 2 of the study occurred 12 months later when mothers were sent a postal questionnaire requesting information about the child's health and development during the first year of life using the Denver Prescreening Developmental Questionnaire. Seven hundred and forty-four (85.4%) European mothers returned the postal questionnaire. SGA children were not at increased risk of developmental delay at 12 months of age. In a sample representative of New Zealand European children, after adjustment for the effects of potential confounders, maternal smoking during pregnancy (OR = 2.1 [95% CI 1.1, 4.0]), maternal smoking during the first year of life (OR = 1.9 [95% CI 1.0, 3.8]) and low levels of satisfaction with parenting (OR = 2.4 [95% CI 1.1, 5.2]) were associated with significantly increased risk of developmental delay. In the subgroup of SGA children, maternal smoking during pregnancy (OR = 2.9 [95% CI 1.4, 6.2]), high levels of stress associated with parenting (OR = 2.2 [95% CI 1.2, 4.0]), and low levels of satisfaction with parenting (OR = 4.3 [95% CI 1.3, 13.5]) were significantly associated with developmental delay after adjustment for the effects of potential confounders. In conclusion, maternal and postnatal factors were better predictors of developmental delay than demographic variables.     

Evidence for an association between environmental tobacco smoke exposure and birthweight: a meta-analysis and new data

Because of the strong association of active smoking with fetal growth retardation, increasing interest has focused on whether there is also an association with exposure to environmental tobacco smoke (ETS). We examined this issue in a retrospective study and by conducting a review of the literature and data pooling. In our study, nonsmoking women with singleton livebirths born in 1986–87 ( n  = 992) provided information on exposure to ETS for 1 h or more per day and paternal smoking. The risk of low birthweight (LBW, < 2500 g) was not increased in infants of ETS-exposed women, but there was a somewhat increased risk for LBW at term (adjusted odds ratio [OR] 1.8, 95% confidence interval [CI] 0.6, 4.8) and small-for-gestational-age (< 10th percentile of weight; OR = 1.4, 95% CI = 0.8, 2.5). These results were in the range of 16 other studies in the literature that had odds ratios from 1.0 to 2.2. A weighted average of the results of all studies on LBW at term or small-for-gestational-age yielded a pooled estimate of 1.2 [95% CI = 1.1, 1.3] in nonsmoking women. The pooled estimate of mean birthweight indicated a decrement of 28 g with ETS exposure of nonsmoking women [95% CI = −41, −16], with a greater decrement (about 40 g) seen among more homogeneous studies.     

Active and passive maternal smoking during pregnancy and the risks of low birthweight and preterm birth: the Generation R Study

The objective of this study was to examine the associations between active and passive smoking in different periods of pregnancy and changing smoking habits during pregnancy, with low birthweight and preterm birth. The study was embedded in the Generation R Study, a population-based prospective cohort study from early fetal life onwards in Rotterdam, The Netherlands. Active and passive smoking were assessed by questionnaires in early, mid- and late pregnancy. Analyses were based on 7098 pregnant women and their children. Active smoking until pregnancy was ascertained and was not associated with low birthweight and preterm birth. Continued active smoking after pregnancy was also recorded and was associated with low birthweight (adjusted odds ratio 1.75 [95% CI 1.20, 2.56]) and preterm birth (adjusted odds ratio 1.36 [95% CI 1.04, 1.78]). The strongest associations were found for active maternal smoking in late pregnancy. Passive maternal smoking in late pregnancy was associated with continuously measured birthweight (P for trend <0.001). For all active smoking categories in early pregnancy, quitting smoking was associated with a higher birthweight than continuing to smoke. Tendencies towards smaller non-significant beneficial effects on mean birthweight were found for reducing the number of cigarettes without quitting completely. This study shows that active and passive smoking in late pregnancy are associated with adverse effects on weight and gestational age at birth. Smoking in early pregnancy only, seems not to affect fetal growth adversely. Health care strategies for pregnant women should be aimed at quitting smoking completely rather than reducing the number of cigarettes.     

Maternal alcohol and coffee drinking, parental smoking and childhood leukaemia: a French population-based case-control study

We investigated the role of maternal alcohol and coffee drinking during pregnancy and that of parental smoking in the aetiology of childhood leukaemia. A French, population-based, case-control study was conducted, comparing 472 [407 acute lymphoblastic leukaemia (ALL) and 62 acute myeloblastic leukaemia] cases of childhood acute leukaemia (AL) and 567 population controls, frequency-matched with cases on age, gender and region of residence. Both case and control mothers filled in a comprehensive self-administered standardised questionnaire, eliciting detailed data on maternal alcohol and coffee consumption during pregnancy and parental smoking before, during and after pregnancy. Maternal alcohol consumption of more than 1 drink per day was related to ALL (OR = 2.8 [95% CI 1.8, 5.9]). While maternal coffee consumption was not significantly related to AL (OR = 1.4 [95% CI 0.9, 2.3]), highest intake of coffee (more than 3 cups per day) during pregnancy was associated with AL in children whose mothers were non-smokers (OR = 1.9 [95% CI 1.0, 3.5]). No association with parental smoking, either maternal or paternal, was observed with AL. The present results suggest a possible role of the highest consumption of alcohol by the mother during pregnancy in the aetiology of childhood AL.     

Birthweight and caffeine consumption

OBJECTIVES: To assess the association between maternal caffeine consumption during pregnancy and low birth weight, prematurity and intrauterine growth retardation. METHODS: A case-control was carried out and 354 newborns of single labor with birthweight <2,500 g (cases) and 354 with birthweight >3,000 g (controls) were analyzed. Caffeine consumption was calculated based on daily consumption of coffee, soft drinks and tea. Results were adjusted using multiple logistic regression for the following confounders: mother's age, schooling, income, marital status, skin color, parity, smoking, previous low birthweight children, mother's pre-pregnancy weight, employment status, interval between pregnancies, prenatal care and high blood pressure. RESULTS: For caffeine consumption <300 mg/day and >300 mg/day, the adjusted odds ratios for low birthweight were: 0.72 (95%IC=0.45-1.25) and 0.47 (95%IC=0.24-0.92); prematurity: 0.59 (95%IC=0.32-1.09) and 0.32 (95%IC=0.15-0.72); and intrauterine growth retardation: 1.16 (95%IC=0.45-3.01) and 0.64 (95%IC=0.20-1.98), respectively. CONCLUSION: There was no association between caffeine consumption during pregnancy and low birthweight, prematurity and intrauterine growth retardation.     

Determinants of caesarean section in Lebanon: geographical differences

This study, based on the Lebanese National Perinatal Survey which included 5231 women, examined the relations between the caesarean section (CS) rate and the characteristics of mothers, children, antenatal care and maternity units in two geographical zones of Lebanon (Beirut-Mount Lebanon and the rest of the country) and then looked at geographical variations. This analysis concerned 3846 women with singleton pregnancies and livebirths at low risk of CS, after exclusion of women with a previous CS, non-cephalic fetal presentations, or delivery before 37 weeks' gestation. The principal end point was caesarean delivery. The relations between the factors studied and CS were estimated by odds ratios (OR), both crude and adjusted, using logistic regression. The rate of CS was higher in the Beirut-Mount Lebanon zone than elsewhere (13.4% vs. 7.6%). After adjustment, several factors remained associated with caesarean delivery in each zone. Common factors were primiparity, gestational age > or = 41 weeks and antenatal hospitalisation. Factors identified only in the Beirut-Mount Lebanon zone were obstetric history and insurance coverage, whereas for the other zones we only found major risk factors for obstetric disease: maternal age > or = 35 years, number of antenatal consultations > or = 4 and birthweight < or = 2500 g. The multivariable analysis of the overall population, adjusting for zone of delivery and other variables, shows that zone was one of the principal factors associated with the risk of caesarean delivery in Lebanon (OR = 1.80 [95% CI 1.09, 2.95]). In conclusion, the CS rates in Lebanon were high, with geographical differences that were associated with access to care and with obstetric practices.     

Self-reported experiences of racial discrimination and Black-White differences in preterm and low-birthweight deliveries: the CARDIA Study

OBJECTIVES: We examined the effects of self-reported experiences of racial discrimination on Black-White differences in preterm (less than 37 weeks gestation) and low-birthweight (less than 2500 g) deliveries. METHODS: Using logistic regression models, we analyzed data on 352 births among women enrolled in the Coronary Artery Risk Development in Young Adults Study. RESULTS: Among Black women, 50% of those with preterm deliveries and 61% of those with low-birthweight infants reported having experienced racial discrimination in at least 3 situations; among White women, the corresponding percentages were 5% and 0%. The unadjusted odds ratio for preterm delivery among Black versus White women was 2.54 (95% confidence interval [CI]=1.33, 4.85), but this value decreased to 1.88 (95% CI=0.85, 4.12) after adjustment for experiences of racial discrimination and to 1.11 (95% CI=0.51, 2.41) after additional adjustment for alcohol and tobacco use, depression, education, and income. The corresponding odds ratios for low birthweight were 4.24 (95% CI=1.31, 13.67), 2.11 (95% CI=0.75, 5.93), and 2.43 (95% CI=0.79, 7.42). CONCLUSIONS: Self-reported experiences of racial discrimination were associated with preterm and low-birthweight deliveries, and such experiences may contribute to Black-White disparities in perinatal outcomes.     

A population-based cohort study of the relation between maternal birthweight and risk of gestational diabetes mellitus in four racial/ethnic groups

Intrauterine growth retardation and low birthweight have been associated with an increased risk of insulin resistance and type II diabetes later in life. We hypothesised that maternal low birthweight is associated with an increased risk of gestational diabetes mellitus (GDM). Study subjects comprised women giving birth in Washington State between 1987 and 1995. Information for 21,528 births to non-Hispanic white women, 6359 to African-American women, 7456 to Native American women and 6496 to Hispanic women was available for analysis. All information was derived from statewide computerised vital records and hospital discharge summaries of obstetric and neonatal admissions with linkage to birth certificates of mothers. Maternal birthweight was collected from subjects' birth certificates. Information from both the birth certificates and the obstetric and neonatal admissions database was used to determine whether subjects developed GDM. Poisson regression models were estimated to calculate unadjusted and adjusted risk ratios (RRs) and 95% confidence intervals (CIs) for GDM by categories of maternal birthweight. The cumulative incidence of GDM among non-Hispanic white, African-American, Native American and Hispanic women was 2.8, 2.6, 2.7 and 3.0% respectively. After adjusting for maternal age, parity, cigarette smoking, history of chronic hypertension and participation in the Medicaid programme, non-Hispanic white women with a birthweight < 2000 g were 1.7 times more likely to have had their pregnancy complicated by GDM (RR = 1.7; 95% CI 0.8, 3.3) than those with a birthweight 3000-3999 g. The corresponding adjusted RRs for African-American, Native American, and Hispanic women were 2.8 [95% CI 1.2, 6.1], 3.1 [95% CI 1.2, 8.2] and 2.4 [95% CI 0.9, 6.0] respectively. Among African-American women, those with a birthweight > or = 4000 g also experienced a twofold increased risk of GDM (RR = 2.1; 95% CI 1.0, 4.1). This association of high birthweight and increased GDM risk was not found among women in the other three racial/ethnic groups. These findings suggest that individuals with low birthweight constitute a group at increased risk for GDM.     

Risk factors for Aboriginal low birthweight, intrauterine growth retardation and preterm birth in the Darwin Health Region

Abstract: Risk factors for Aboriginal low birthweight (< 2500 g), preterm birth (< 37 weeks' gestation) and intrauterine growth retardation (under the tenth percentile of Australian birthweights for gestational age) were examined in 503 live–born singletons recorded as born to an Aboriginal mother and routinely delivered at the Royal Darwin Hospital between January 1987 and March 1990. Infants born to mothers with body mass index less than 18.5 kg/m² had five times the risk of having low birthweight and 2.5 times the risk of intrauterine growth retardation. Population–attributable risk percentages suggest that 28 per cent of low birthweight and 15 per cent of growth retardation could be attributed to maternal malnutrition. Risk percentages for maternal smoking of more than half a packet of cigarettes a day were 18 per cent for low birthweight and 10 per cent for growth retardation. For growth retardation, 18 per cent could be attributed to a maternal age under 20 years. Risk factors for preterm birth were predominantly obstetric: the population–attributable risk percentage for pregnancy–induced hypertension was 26 per cent and for other obstetric conditions was 16 per cent. For Aboriginal births in the Darwin Health Region, maternal malnutrition and smoking are key elements in the prevention of low birthweight and intrauterine growth retardation. Teenage pregnancy is an important risk for intrauterine growth retardation, and pregnancy–induced hypertension is a risk for preterm birth.     

Birth characteristics and brain cancers in young children

BACKGROUND: High birthweight is a potential risk factor for childhood brain tumours, particularly astrocytomas. We investigated several birth characteristics in relationship to brain cancers in young children. METHODS: We obtained 849 invasive central nervous system (CNS) cancer cases, ages 0-4 years, from California's population-based cancer registry for 1988-1997. We matched 746 (88%) of these cases to a California live birth certificate. We randomly selected two control birth certificates for each case, matched on date of birth and gender. We used conditional logistic regression to obtain odds ratios (OR) and 95% CI. The birth characteristics examined included birthweight, gestational age, race, parental age, and parental education. RESULTS: Analysing all CNS tumours combined, we found that children of other racial/ ethnic groups had OR below one compared with non-Hispanic white children. When adjusted for gestational age, race/ethnicity, and mother's place of birth, the OR for high birthweight (>/=4000 g) was 1.05 (95% CI: 0.79-1.38) compared with children with birthweights of 2500-3999 g. For astrocytomas (313 cases), the adjusted OR for high birthweight was 1.40 (95% CI: 0.90-2.18). When parental education was included in the model (available for only a subset of the birth years), the adjusted OR was 1.71 (95% CI: 1.01-2.90). High birthweight did not appear to be a risk factor for primitive neuroectodermal tumours (PNET). CONCLUSIONS: We found high birthweight associated with increased risk of astrocytomas, but not PNET, in young children.     

Maternal posture and its influence on birthweight

OBJECTIVE: To analyze the relationship between maternal posture/physical activity and inadequate birthweight. METHODS: Prospective cohort study involving 152 pregnant women from a public low-risk antenatal care facility. Three interviews evaluating the frequency of physical activity were administered to each pregnant woman during gestation. Birthweight (inadequate when <3,000 g and adequate when > or =3,000 g) was the dependent variable and the frequency of physical activity the independent variable. Statistical analysis was performed using logistic univariate analysis and multiple regression controlling for schooling, smoking, living with spouse, and baseline nutritional status. RESULTS: The practice of walking for at least 50 minutes during the first period of pregnancy was identified as a protective factor against inadequate birthweight (adjusted OR=0.44; 95% CI: 0.20-0.98). Standing for 2.5 hours or longer during the second semester of pregnancy was associated with increased risk (adjusted OR=3.23; 95% CI: 1.30-7.99). Dose-response relationships were identified for washing clothing by hand and cooking (p-value for linear trend <0.01 and 0.05, respectively). After confounder control, only washing clothing during the second trimester of gestation remained statistically significant. CONCLUSIONS: Our results show the importance of medical orientation regarding posture and physical activity during antenatal care, aiming at the reduction of inadequate birthweight.     

Ethnic differences in the growth of low-birthweight infants

Differences in growth were investigated among ethnic groups in low-birthweight babies (<2500 g or <32 weeks gestation) at birth and at 2–3 years. This prospective study was based on data for all 3091 low-birthweight live births in the South East Thames Region, UK, over a 1-year period, surviving to discharge from hospital. Weights were recorded at birth and at 2–3 years for 998 babies, and head circumferences for 859. These were compared with the UK 1990 reference standards. Ethnic differences were adjusted for parity, multiple birth, smoking and alcohol during pregnancy, mother's height, weight and age, marital status, partner's support and social class. At 2–3 years, there was substantial average catch-up growth only for the weight of infants of 32 weeks' gestation. Babies <32 weeks gestation had fallen behind. Head circumferences had failed to keep up or had fallen behind for both groups. The ethnic groups had similar birthweight standard deviation scores (SDS). At 2–3 years, Black babies of <32 weeks' gestation had gained in weight and head circumference compared with White babies (adjusted difference in weight SDS: 0.71, [95% CI 0.28, 1.13]). Asian babies of at least 32 weeks' gestation had smaller heads than White, a difference that increased with time. It was concluded that ethnic differences in the growth of low-birthweight infants are related to gestational age. Although most of the babies born at <28 weeks' gestation were close to their birthweight reference standards, only the Black infants had maintained their position at 2–3 years. Black infants, particularly when born preterm, tend to put on more weight than White.     

Explaining educational inequalities in birthweight: the Generation R Study

Although low socio-economic status has consistently been associated with lower birthweight, little is known about the factors whereby socio-economic disadvantage influences birthweight. We therefore examined explanatory mechanisms that may underlie the association between the educational level of pregnant women, as an indicator of socio-economic status, and birthweight. The study was embedded within a population-based cohort study in the Netherlands. Information on maternal education, offspring's birthweight and several determinants of birthweight was available for 3546 pregnant women of Dutch origin.
Infants of the lowest educated women had a statistically significantly lower birthweight than infants of the highest educated women [difference adjusted for gender and gestational age: −123 g (95% CI −167, –79)]. Parity, age of the pregnant women, hypertension, parental height and parental birthweight, marital status, pregnancy planning, financial concerns, number of people in household, weight gain and smoking habits individually explained part of the differences in birthweight, while adjustment for working hours and body mass index resulted in increases in birthweight differences between the educational levels. After full adjustment, the difference in birthweight between lowest and highest education was reduced by 66%. Our study confirmed remarkable educational inequalities in birthweight, a large part of which was explained by pregnancy characteristics, anthropometrics, the psychosocial and material situation, and lifestyle-related factors. Altering smoking habits may be an option to reduce educational differences in birthweight, as many lower-educated women tend to continue smoking during pregnancy. In order to tackle inequalities in birthweight, it is important that interventions are accessible for pregnant women in lower socio-economic strata.     

Maternal ethnicity and pre-eclampsia in New York City, 1995-2003

Studies on ethnic differences in the risk of pre-eclampsia are limited. We linked birth records for 902,460 singleton births for the period 1995-2003 in New York City with hospital discharge data to evaluate the association between ethnicity and the risk of pre-eclampsia and compare risks between US-born and foreign-born women. Logistic regression models adjusted for maternal age, maternal education, parity, self-reported pre-pregnancy maternal weight, smoking during pregnancy and year of delivery were used to compare each ethnic group with non-Hispanic White women. The prevalence of pre-eclampsia in this study population was 3.2%. Among the major ethnic groups considered in our study, East Asian women had the lowest risk of pre-eclampsia (1.4%) and Mexican women had the highest risk (5.0%). Compared with non-Hispanic White women, there was a slightly decreased risk for East Asian women (adjusted OR = 0.8, [95% CI 0.7, 0.8]), similar risk for North African women (adjusted OR = 1.1, [95% CI 0.9, 1.3]), and increased risk for all other major ethnic groups (adjusted ORs: 1.3, 2.9), with the highest risk for Mexican women (adjusted OR = 2.9, [95% CI 2.7, 3.1]). No difference in risks was observed for US- vs. foreign-born women with the exception that foreign-born South-East Asian and Pacific Islanders had an increased risk of pre-eclampsia (adjusted OR = 1.8, [95% CI 1.0, 3.1]) relative to those born in the US. We concluded that there was ethnic heterogeneity in the development of pre-eclampsia among women in New York City and that Asian subgroups should be examined separately in future studies on ethnicity. Our results should contribute to screening for pre-eclampsia taking ethnic variation into account, and may help to suggest leads for the study of the aetiology of the condition.