For decades, researchers have known that heavy drinking during pregnancy can cause fetal alcohol syndrome and other birth defects. But the potential effects of small amounts of alcohol on a developing baby are not well understood. Moreover, nearly half of all pregnancies in the United States are unplanned, so many women do not know they are pregnant for up to four to six weeks, which may expose the developing child to the toxic effects of ethanol.
Why Is Alcohol Dangerous During Pregnancy?
According to the CDC, alcohol in the mother’s blood easily passes to the child through the umbilical cord. Miscarriage, stillbirth and a plethora of lifelong physical, behavioral and intellectual disabilities are associated with maternal drinking. Collectively, these disabilities are known as fetal alcohol spectrum disorders (FASDs). Children with FASDs may incur the following characteristics and behaviors:
- Abnormal facial features, such as a smooth philtrum (the ridge between the nose and upper lip)
- Shorter stature
- Low body weight
- Poor coordination
- Hyperactive behavior
- Difficulty with attention
- Poor memory
- Difficulty in school, particularly with mathematics
- Learning disabilities
- Delays in speech and language
- Cognitive deficits and low IQ
- Impaired reasoning and judgment skills
- Sleep and sucking problems as a baby
- Vision or hearing disorders
- Disease of the heart, kidney or bone
Yet in spite of these known risk factors and outcomes, the research of the impact of low-level alcohol consumption during pregnancy is scant and inconclusive. Recently, a meta-analysis by Marmluc and Edwards, et al., (BMJ 2017) sought to establish guidelines for clinicians regarding alcohol consumption during pregnancy. Searching Medline, Embase, Web of Science and Psychinfo from inception to 11 July 2016, the team extracted and reviewed data for inclusion. In all, 24 cohort and two quasi-experimental studies were included for analysis.
With the exception of small birth size and gestational age, there was insufficient data to make any robust conclusions. Accordingly, odds ratio estimates of babies statistically small for their gestational age (SGA) and preterm birth were higher among babies whose mothers consumed up to 32 g/week versus no alcohol consumption, yet estimates for preterm birth were also compatible with no association. (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.
Evidence germane to effects of drinking ≤32 g/week in pregnancy is sparse. Yet there was evidence that even light prenatal alcohol consumption is associated with SGA and preterm delivery. The message for clinicians is clear, in spite of the paucity of evidence.
Why Does This Matter?
In many areas of the world, alcohol drinking is a common practice, including drinking during pregnancy. But the evidence is limited, as the spectrum of subclinical forms of FAS are not well understood, and therefore what we don’t know can hurt an unborn child. Therefore, abstention from any alcohol or unprescribed drug consumption during pregnancy is the safest practice and the best advice a physician can give.