Caffeine causes miscarriage

Caffeine is among the most frequently consumed drugs in the world. Caffeine will cross the placenta to the fetus during pregnancy. Several studies have suggested that caffeine use by pregnant women may increase the risk of miscarriage. One limitation of these studies is the effect of “morning sickness”. It has been known for some time that women who have morning sickness, have a lower rate of pregnancy complications including miscarriage. Since women who have nauseous are less likely to dring caffeine, some experts believed that this made it appear as though caffeine was increasing the miscarriage risk.

Caffeine and miscarriage study

From 1996 until 1998, doctors in the San Francisco area conducted a study in pregnant women to determine the effect of caffeine use on miscarriage risk. All women who suspected that they were pregnant had a blood pregnancy test to confirm pregnancy.

Information on caffeine use was obtained in interviews conducted with the women soon after their pregnancy was confirmed. On average, the interview was conducted around the 70th day of pregnancy. In addition to finding out about their caffeine use, the interviewers also asked about other factors thought to be associated with miscarriage such as previous miscarriages, smoking, alcohol use, and nausea and vomiting.

Caffeine use was categorized as none, less than 200 mg per day or more than 200 mg per day.

Caffeine and miscarriage study results

 Just over 1000 pregnant women agreed to be interviewed for this study. Sixteen percent of these women miscarried. Women who drank less than 200 mg of cafeine daily had slightly higher miscarriage rates than women who did not drink any caffeine. women who drank more than 200 mg of caffeine a day had almost double the rate of miscarriage. Some women reduced their caffeine intake after learning they were pregnant.  However, the results indicated that this did not lower their chances for miscarriage compared to women who maintained their caffeine intake at the same amount.

What is the effect of morning sickness and other variables of the results?

The association between the use of caffeine and miscarriage persisted among women both with and without morning sickness. Nonsmokers were more sensitive to the effects of caffeine. Nonsmoking caffeine users had a higher rate of miscarriage. The results were similar whether women consumed their caffeine from coffee drinking or from other sources. Caffeine use was associated with an increase in early miscariage (before 8 weeks) as well as late miscarriage (after 8 weeks).