Week-by-week alcohol consumption in early pregnancy and spontaneous abortion risk: a prospective cohort study
Spontaneous abortion occurs in an estimated 1 in 6 recognized pregnancies and can come at a great emotional cost.
- Alcohol use may increase the risk of spontaneous abortion through several potential mechanisms:
- oxidative stress secondary to alcohol consumption may disrupt biochemical pathways involved in embryogenesis,
- exposure can hinder retinoic acid synthesis, thereby affecting epigenetic programming and cell lineage determination, and
- alcohol use can alter maternal hormone levels, affecting uterine receptivity.
Studies of alcohol use and spontaneous abortion are often hindered by methodologic shortcomings such as recall bias and imprecision in determining gestational age at pregnancy loss. Many recruit participants during prenatal care, meaning enrollment takes place later in gestation than many spontaneous abortions occur. Others are vulnerable to selection bias because of recruitment methods that differ by pregnancy outcome.
In this prospective cohort, researchers had the opportunity to recruit participants representative of the general obstetrical population. They were enrolled while planning a pregnancy or in early pregnancy and reported alcohol use both before and after any change in alcohol consumption.
Among the 5353 participants, 49.7% reported using alcohol during early pregnancy and 12.0% miscarried.
Median gestational age at change in alcohol use was 29 days.
Alcohol use during weeks 5 through 10 from last menstrual period was associated with increased spontaneous abortion risk, with risk peaking for use in week 9.
This window aligns with the embryonic stage of development, when organogenesis is occurring and pregnancy is most vulnerable to insults. These findings persisted when excluding women who reported binge alcohol use.
Each successive week of alcohol use was associated with an 8% increase in spontaneous abortion relative to those who did not consume alcohol. This risk is cumulative.
In addition, risk was not related to number of alcoholic drinks per week, beverage type, or binge alcohol use.
Women who were older than 35 years, white, college-educated, and from high-income households were most likely to use alcohol. Although this is not the population generally flagged for high-risk behaviors, these demographics are consistently linked with alcohol use during pregnancy.
Researchers believe clinical biases may result in these women being overlooked for risk counseling even though this group is at the greatest risk for continued alcohol use.
Studies not accounting for alcohol exposure in early pregnancy obscure the time-dependent effect of alcohol use and underestimate risk.
In this prospective cohort, the researchers find that risk of spontaneous abortion accumulates with each successive week of alcohol use, even at low levels of consumption and when excluding binge alcohol use.
These findings underscore the warning of no known safe amount of alcohol in pregnancy.
Half of women use alcohol in the first weeks of gestation, but most stop once pregnancy is detected. The relationship between timing of alcohol use cessation in early pregnancy and spontaneous abortion risk has not been determined.
This study aimed to evaluate the association between week-by-week alcohol consumption in early pregnancy and spontaneous abortion.
Participants in Right from the Start, a community-based prospective pregnancy cohort, were recruited from 8 metropolitan areas in the United States (2000–2012).
In the first trimester, participants provided information about alcohol consumed in the prior 4 months, including whether they altered alcohol use; date of change in use; and frequency, amount, and type of alcohol consumed before and after change.
The researchers assessed the association between spontaneous abortion and week of alcohol use, cumulative weeks exposed, number of alcoholic drinks per week, beverage type, and binge alcohol consumption.
- Among 5353 participants, 49.7% reported using alcohol during early pregnancy and 12.0% miscarried.
- Median gestational age at change in alcohol use was 29 days (interquartile range, 15–35 days).
- Alcohol use during weeks 5 through 10 from last menstrual period was associated with increased spontaneous abortion risk, with risk peaking for use in week 9.
- Each successive week of alcohol use was associated with an 8% increase in spontaneous abortion relative to those who did not drink (adjusted hazard ratio, 1.08; 95% confidence interval, 1.04–1.12).
- This risk is cumulative.
- In addition, risk was not related to number of drinks per week, beverage type, or binge drinking.
Each additional week of alcohol exposure during the first trimester increases risk of spontaneous abortion, even at low levels of consumption and when excluding binge alcohol use.