Women who drink light-to-moderately during pregnancy have been observed to have lower risk of unfavourable pregnancy outcomes than abstainers. This has been suggested to be a result of bias. In a pooled sample, including 193 747 live-born singletons from nine European cohorts, we examined the associations between light-to-moderate drinking and preterm birth, birth weight, and small-for-gestational age in term born children (term SGA). To address potential sources of bias, we compared the associations from the total sample with a sub-sample restricted to first-time pregnant women who conceived within six months of trying, and examined whether the associations varied across calendar time. In the total sample, drinking up to around six drinks per week as compared to abstaining was associated with lower risk of preterm birth, whereas no significant associations were found for birth weight or term SGA. Drinking six or more drinks per week was associated with lower birth weight and higher risk of term SGA, but no increased risk of preterm birth. The analyses restricted to women without reproductive experience revealed similar results. Before 2000 approximately half of pregnant women drank alcohol. This decreased to 39% in 2000-2004, and 14% in 2005-2011. Before 2000, every additional drink was associated with reduced mean birth weight, whereas in 2005-2011, the mean birth weight increased with increasing intake. The period-specific associations between low-to-moderate drinking and birth weight, which also were observed for term SGA, are indicative of bias. It is impossible to distinguish if the bias is attributable to unmeasured confounding, which change over time or cohort heterogeneity.

Published in Pregnant Women

OBJECTIVES: To determine the effects of low-to-moderate levels of maternal alcohol consumption in pregnancy on pregnancy and longer-term offspring outcomes.

SEARCH STRATEGY: Medline, Embase, Web of Science and Psych info from inception to 11 July 2016.

SELECTION CRITERIA: Prospective observational studies, negative control and quasi experimental studies of pregnant women estimating effects of light drinking in pregnancy (</=32 g/week) versus abstaining. Pregnancy outcomes such as birth weight and features of fetal alcohol syndrome were examined.

DATA COLLECTION AND ANALYSIS: One reviewer extracted data and another checked extracted data. Random effects meta-analyses were performed where applicable, and a narrative summary of findings was carried out otherwise.

MAIN RESULTS: 24 cohort and two quasi experimental studies were included. With the exception of birth size and gestational age, there was insufficient data to meta-analyse or make robust conclusions. Odds of small for gestational age (SGA) and preterm birth were higher for babies whose mothers consumed up to 32 g/week versus none, but estimates for preterm birth were also compatible with no association: summary OR 1.08, 95% CI (1.02 to 1.14), I2 0%, (seven studies, all estimates were adjusted) OR 1.10, 95% CI (0.95 to 1.28), I2 60%, (nine studies, includes one unadjusted estimates), respectively. The earliest time points of exposure were used in the analysis.

CONCLUSION: Evidence of the effects of drinking </=32 g/week in pregnancy is sparse. As there was some evidence that even light prenatal alcohol consumption is associated with being SGA and preterm delivery, guidance could advise abstention as a precautionary principle but should explain the paucity of evidence.

Published in Pregnant Women

BACKGROUND: Evidence is conflicting regarding the relationship between low maternal alcohol consumption and birth outcomes. This paper aimed to investigate the association between alcohol intake before and during pregnancy with birth weight and gestational age and to examine the effect of timing of exposure.

METHODS: A prospective cohort in Leeds, UK, of 1303 pregnant women aged 18-45 years. Questionnaires assessed alcohol consumption before pregnancy and for the three trimesters separately. Categories of alcohol consumption were divided into 2 units/week with a non-drinking category as referent. This was related to size at birth and preterm delivery, adjusting for confounders including salivary cotinine as a biomarker of smoking status.

RESULTS: Nearly two-thirds of women before pregnancy and over half in the first trimester reported alcohol intakes above the Department of Health (UK) guidelines of 2 units/week before pregnancy and in trimesters 1 and 2 compared to non-drinkers. Even women adhering to the guidelines in the first trimester were at significantly higher risk of having babies with lower birth weight, lower birth centile and preterm birth compared to non-drinkers, after adjusting for confounders (p<0.05).

CONCLUSIONS: We found the first trimester to be the period most sensitive to the effect of alcohol on the developing fetus. Women adhering to guidelines in this period were still at increased risk of adverse birth outcomes. Our findings suggest that women should be advised to abstain from alcohol when planning to conceive and throughout pregnancy.

Published in Pregnant Women

OBJECTIVE: To investigate the association between alcohol consumption and binge drinking before and during early pregnancy and adverse pregnancy outcomes.

METHODS: We used data from 5,628 nulliparous pregnant participants recruited to the Screening for Pregnancy Endpoints (SCOPE) study, a prospective cohort study. Participants were interviewed at 15 weeks of gestation and information on alcohol intake before pregnancy and until the time of interview was obtained using a standardized questionnaire. Alcohol intake was classified as occasional (1-2 units per week), low (3-7 units per week), moderate (8-14 units per week), and heavy (greater than 14 units per week). Binge alcohol consumption was defined as consumption of 6 or more alcohol units in one session.

RESULTS: Of the 5,628 participants, 1,090 (19%) reported occasional alcohol consumption, 1,383 (25%) low alcohol consumption, 625 (11%) moderate alcohol consumption, and 300 (5%) heavy alcohol consumption. Overall, 1,905 (34%) participants reported binge alcohol consumption in the 3 months before pregnancy, and 1,288 (23%) of these participants reported binge alcohol consumption during the first 15 weeks of pregnancy. Participants who consumed occasional to heavy amounts of alcohol in early pregnancy did not have altered odds of a small-for-gestational-age neonate, reduced birth weight, preeclampsia, or spontaneous preterm birth. Similarly, those who binge drank in early pregnancy did not have altered odds of these adverse pregnancy outcomes.

CONCLUSION: Alcohol consumption in early pregnancy was prevalent in this nulliparous cohort. There was no association between alcohol consumption before 15 weeks of gestation and small for gestational age, reduced birth weight, preeclampsia, or spontaneous preterm birth. LEVEL OF EVIDENCE: : II

Published in Pregnant Women

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