Miscarriage risk increases with each week of alcohol consumption during pregnancy

The risk for miscarriage increases with each week of alcohol consumption in early pregnancy, regardless of the amount consumed, according to a study published in the American Journal of Obstetrics and Gynecology.

“Abstaining from alcohol around conception or during pregnancy has long been advised for many reasons, including preventing fetal alcohol syndrome,” Katherine Hartmann, MD, PhD, vice president for Research Integration at Vanderbilt University Medical Center, said in a press release.

Despite this, Hartmann said that many people view modest alcohol consumption as being safe during this time.

“For this reason, our findings are alarming,” she said. “Levels of use that women, and some care providers, may believe are responsible are harmful, and no amount can be suggested as safe regarding pregnancy loss.”

Hartmann and colleagues evaluated participants in a community-based prospective cohort study, which included women from eight metropolitan regions in the United States who were enrolled from 2002 to 2012.

Women aged 18 years and older were recruited prior to 12 weeks gestation. They completed intake interviews at baseline and again during their first trimester.

During the first trimester interview, women reported detailed information about their alcohol consumption in the previous 4 months, including whether they had changed their alcohol use during that time. The researchers determined the gestational age based on participants’ last menstrual period.

Hartmann and colleagues corroborated self-reported pregnancy outcomes with data from medical records, birth certificates and vital records. They defined spontaneous abortion as a pregnancy loss prior to 20 weeks gestation, and compared those with pregnancies past 20 weeks gestation.

The researchers assessed associations between spontaneous abortion and alcohol use, including the number of weeks exposed, number of drinks consumed per week and binge drinking.

A total of 5,353 women participated in the study, of whom 49.7% reported alcohol use in early pregnancy. Among the participants, 12% experienced a miscarriage.

Hartmann and colleagues reported that the median gestational age at the time of change in alcohol use was 29 days.

The researchers found that alcohol use from week 5 through week 10 of a woman’s last reported menstrual period was associated with an increased risk for spontaneous abortion, with the highest risk at week 9.

Compared with those who did not drink, each successive week of alcohol use during pregnancy was associated with an 8% increase in risk for spontaneous abortion (adjusted HR = 1.08; 95% CI, 1.04-1.12).

The researchers noted that the observed risk for spontaneous abortion was cumulative and strongest from week 5 through week 10, which aligns with when organogenesis occurs in the embryonic stage of development and when a pregnancy is most vulnerable.

Additionally, Hartmann and colleagues found that the risk for spontaneous abortion was not associated with the number of drinks consumed each week, the type of alcohol consumed or binge drinking.

The researchers said the findings demonstrate that no amount of alcohol consumption is safe during pregnancy.

In the press release, they stressed that the use of home pregnancy tests and stopping alcohol consumption if planning to become pregnant are vital in avoiding a spontaneous abortion.

“Efforts to promote early pregnancy recognition and cessation of alcohol use are warranted to curtail risk of spontaneous abortion,” they wrote.