Association between maternal smoking and low birth weight in Switzerland: the EDEN study.
(49/1489)
PURPOSE: To study the association between maternal smoking during pregnancy and low birth weight (LBW), small-for-gestational-age birth weight (SGA) and preterm birth, and to quantify the population-attributable fractions for these outcomes in Switzerland. METHODS: Data were gathered for all births in the Canton of Vaud (Switzerland) over a twelvemonth period in 1993-1994. LBW was defined as birth weight <2500 g, SGA as a birth weight <10th percentile for gestational age, and preterm birth as a birth occurring at a gestational age <37 weeks. Maternal smoking before and during pregnancy was recorded. RESULTS: Of a total of 6284 singleton births, 303 (4.8%) were LBW, 731 (11.7%) were SGA, and 364 (5.8%) were preterm. 19.1% of the mothers reported smoking during pregnancy ("smokers"). Mean birth weight, adjusted for maternal age, parity, parents' occupation and neonates' sex and nationality, was lower by 190 g (95% confidence interval: 150-220) in babies of smokers than those of non-smokers. Comparing smokers to non-smokers, the adjusted odds ratios were 2.7 (2.1-3.5) for LBW, 2.1 (1.7-2.5) for SGA and 1.4 (1.1-1.9) for preterm birth. Past smoking was not associated with the outcomes. Maternal smoking during pregnancy accounted for 22% (15-29%) of all LBW babies in the population, 14% (10-18%) of SGA and 7% (1-12%) of preterm births. CONCLUSION: Maternal smoking during pregnancy was closely associated with LBW, SGA and preterm birth. A large proportion of these perinatal outcomes could have been prevented in Switzerland if maternal smoking had been avoided. (+info)
Cervical length at 23 weeks' gestation--relation to demographic characteristics and previous obstetric history in South African women.
(50/1489)
OBJECTIVES: To determine the distribution of cervical length in a routine population of singleton pregnancies; to examine the relationship between cervical length, demographic characteristics, and previous obstetric history; and to compare these data with data from a similar study undertaken in the UK. PATIENTS AND METHODS: The study was conducted among women attending routine antenatal clinics at Coronation, Johannesburg General and Chris Hani Baragwanath hospitals. Cervical length was measured by means of transvaginal ultrasound at 23 weeks' gestation in women with singleton pregnancies attending these clinics, as part of a multicentre randomised trial investigating the value of cerclage in a short cervix. The distribution of cervical length was determined and the significance of differences in median cervical lengths between subgroups was calculated according to maternal age, ethnic origin, maternal body mass index (BMI), cigarette smoking, alcohol intake, and previous obstetric history. RESULTS: Cervical screening was offered to women (N = 2 173) attending clinics for a 23-week scan during the study period (July 1999-September 2002). Most women (N = 1 920) accepted, while 253 declined. Complete outcomes (date and mode of delivery, gestation at delivery, birth weight, Apgar scores, maternal blood loss, whether the patient was cerclaged or not, and any complications) were obtained for 1 603 women who accepted screening. Cervical length was measured successfully in all cases. Median cervical length was 33.7 mm and in 64 cases (3.3%) the length was 15 mm or less. Significantly shorter cervical lengths were found in those with a history of previous miscarriage, preterm delivery, those aged less than 20 years and those with an abnormal BMI. Cervical length was not significantly shorter in black women than in coloured and white women. CONCLUSIONS: At 23 weeks' gestation the median cervical length in a South African population was 33.2 mm. In 3.3% of the population the length was < or = 15 mm. There was an association between cervical length, demographic characteristics and previous obstetric history. (+info)
Late pregnancy exposures to disinfection by-products and growth-related birth outcomes.
(51/1489)
Toxicologic studies have demonstrated associations between growth-related birth outcomes and exposure to high concentrations of disinfection by-products (DBPs), including specific trihalomethane (THM) and haloacetic acid (HAA) chemical subspecies. Few prior investigations of DBPs have evaluated exposure during the third trimester of pregnancy, the time period of gestation when fetal growth may be most sensitive to environmental influences. We conducted a retrospective cohort study to examine the effects of exposure to THMs and HAAs during the third trimester and during individual weeks and months of late gestation on the risks for term low birth weight, intrauterine growth retardation, and very preterm and preterm births. The study population (n = 48,119) included all live births and fetal deaths occurring from January 1998 through March 2003 to women whose residence was served by one of three community water treatment facilities. We found evidence of associations between exposure to specific HAAs and term low birth weight as well as intrauterine growth retardation and for exposure to the five regulated HAAs (HAA5) and term low birth weight. Our findings suggest a critical window of exposure with respect to fetal development during weeks 33-40 for the effects of dibromoacetic acid and during weeks 37-40 for the effects of dichloroacetic acid. Adjustment for potential confounders did not affect the conclusions. (+info)
Race, genes and preterm delivery.
(52/1489)
High rates of preterm delivery (PTD) among African Americans are the leading cause of excess infant mortality among African Americans. Failure to fully explain racial disparity in PTD has led to speculation that genetic factors might contribute to this disparity. Current evidence suggests that genetic factors contribute to PTD, but this does not imply that genetic factors contribute to racial disparity in PTD. Environmental factors clearly contribute to PTD. Many of these factors acting over a women's life prior to pregnancy disproportionately affect African Americans and contribute significantly to racial disparity in PTD. Thus, inferring genetic contribution to racial disparity in PTD by attempting to control for environmental factors measured at a single point in time is flawed. There is emerging evidence of gene-environment interactions for PTD, some of which disproportionately affect African Americans. There is also evidence of racial differences in the prevalence of polymorphisms potentially related to PTD. However, to date there is no direct evidence that these differences contribute significantly to racial disparity in PTD. Given the complexity of polygenic conditions such as PTD, the possibility of any single gene contributing substantially to racial disparity in PTD seems remote. (+info)
Genetic variation in the sodium-dependent vitamin C transporters, SLC23A1, and SLC23A2 and risk for preterm delivery.
(53/1489)
Vitamin C has been the focus of epidemiologic investigation in preterm delivery (<37 weeks' gestation), which is a leading cause of neonatal mortality and birth-related morbidity. There are two sodium-dependent membrane transporters encoded by SLC23A1 and SLC23A2, which have key roles in human vitamin C metabolism and which control dietary uptake, reabsorption, and tissue distribution of vitamin C. Using maternal DNA, the authors evaluated common single-nucleotide polymorphisms (SNPs) in SLC23A1 and SLC23A2 in a nested case-control analysis of the Pregnancy, Infection, and Nutrition Study (1995-2000) cohort. Of the associations observed for both haplotypes in SLC23A1 and individual SNPs in SLC23A2, the most robust finding is with an intron 2 variant in SLC23A2. Heterozygotes and homozygotes for this variant had a 1.7-fold (95% confidence interval: 0.9, 3.3) and a 2.7-fold (95% confidence interval: 1.2, 6.3) elevation in the risk of spontaneous preterm birth, respectively. Semi-Bayesian hierarchical regression analysis, which simultaneously adjusted for multiple SNPs within the same gene, gave comparable results. The authors' findings link genetic variants in the vitamin C transporters to spontaneous preterm birth, which may explain previous dietary associations. If the findings from this study are confirmed, they may serve as the foundation for genetic risk assessment of nutritional pathways in preterm birth. (+info)
Laboratory work and pregnancy outcomes: a study within the National Birth Cohort in Denmark.
(54/1489)
AIMS: To examine pregnancy outcomes in women doing laboratory work. METHODS: Using data from the Danish National Birth Cohort (1997-2003), the authors conducted a prospective cohort study of 1025 female laboratory technicians and 8037 female teachers (as reference). The laboratory technicians were asked about laboratory work tasks during pregnancy in an interview (at around 16 weeks of gestation). Pregnancy outcomes were obtained by linking the cohort to the national registers. Hazard ratios (HRs) of late fetal loss and diagnosing of congenital malformations were calculated by using Cox regression, and odds ratios (ORs) of preterm birth and small for gestational age were calculated by using logistic regression. RESULTS: Overall, there were no significant differences in pregnancy outcomes between laboratory technicians and teachers. However, we found that laboratory technicians working with radioimmunoassay or radiolabelling had an increased risk of preterm birth (OR = 2.2, 95% CI 0.8 to 6.2 for radioimmunoassay, and OR = 1.9, 95% CI 0.8 to 4.6 for radiolabelling) and "major" malformations (HR = 2.1, 95% CI 1.0 to 4.7 for radioimmunoassay, and HR = 1.8, 95% CI 0.9 to 3.7 for radiolabelling). The ORs of preterm birth doubled for women working with these tasks every day or several times a week. When an exposure matrix was applied, an increased risk of "major" malformations for exposure to organic solvents was seen. CONCLUSIONS: The results did not indicate any high risk of reproductive failures in laboratory technicians in general. Exposure to radioisotopes may carry a high risk of preterm birth and congenital malformations. This finding deserves further investigation. (+info)
Social class inequalities in perinatal outcomes: Scotland 1980-2000.
(55/1489)
OBJECTIVE: To examine social class inequalities in adverse perinatal events in Scotland between 1980 and 2000 and how these were influenced by other maternal risk factors. DESIGN: Population based study using routine maternity discharge data. SETTING: Scotland. PARTICIPANTS: All women who gave birth to a live singleton baby in Scottish hospitals between 1980 and 2000 (n=1,282,172). MAIN OUTCOME MEASURES: Low birth weight (LBW), preterm birth, and small for gestational age (SGA). RESULTS: The distribution of social class changed over time, with the proportion of mothers with undetermined social class increasing from 3.9% in 1980-84 to 14.8% in 1995-2000. The relative index of inequality (RII) decreased during the 1980s for all outcomes. The RII then increased between the early and late 1990s (LBW from 2.09 (95%CI 1.97, 2.22) to 2.43 (2.29, 2.58), preterm from 1.52 (1.44, 1.61) to 1.75 (1.65, 1.86), and SGA from 2.28 (2.14, 2.42) to 2.49 (2.34, 2.66) respectively). Inequalities were greatest in married mothers, mothers aged over 35, mothers taller than 164 cm, and mothers with a parity of one or more. Inequalities were also greater by the end of the 1990s than at the start of the 1980s for women of parity one or more and for mothers who were not married. CONCLUSION: Despite decreasing during the 1980s, inequalities in adverse perinatal outcomes increased during the 1990s in all strata defined by maternal characteristics. (+info)
Prepregnancy body mass index, vaginal inflammation, and the racial disparity in preterm birth.
(56/1489)
The authors sought to quantify the overall and race/ethnic-specific relations between prepregnancy body mass index and both preterm birth and vaginal inflammation. Data from a cohort of 11,392 women who enrolled in the multicenter Vaginal Infections and Prematurity Study (1984-1989) at 23-26 weeks' gestation were used. Compared with a prepregnancy body mass index of 22, a body mass index of 16 increased the risk of preterm birth by 90% (odds ratio = 1.9, 95% confidence interval (CI): 1.5, 2.6), and a body mass index of 18 increased the risk by 40% (odds ratio = 1.4, 95% CI: 1.2, 1.7). Ethnicity substantially modified the magnitude of the body mass index effect and the shape of the preterm birth risk curve, with underweight having a greater impact on preterm birth among Blacks and Hispanics than among Whites. Low body mass index increased the risk of a high level of neutrophils (> 5 per oil immersion field) and a high vaginal pH measurement (> or = 5.0) among Black women; for a body mass index of 16 versus 22, the odds ratio = 1.7 (95% CI: 1.1, 2.6). Compared with Black women with a body mass index of 22, Blacks with a body mass index of 16 had a 1.7-fold increased risk for a high level of neutrophils and a high vaginal pH measurement, while those with a body mass index of 18 had a 1.3-fold increased risk. (+info)