Women already know they need to cut back on coffee during pregnancy, if not sooner, to lower the risk of miscarriages; but a new study suggests the men in their lives need to limit caffeine too.
Pregnant women who had more than two caffeinated drinks a day while trying to conceive had a 74 percent higher risk of miscarriage than their peers who drank less coffee, tea, soda and energy drinks, the study found.
When their husbands and boyfriends had more than two caffeinated drinks a day during the baby-making phase, however, these pregnant women ended up with almost the same increased risk of miscarriage they would get from drinking coffee or soda themselves.
"We are not saying to stop drinking caffeinated beverages,” said lead study author Germaine Buck Louis of the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Rockville, Maryland.
"Rather, our data suggest that men and women, should they continue to drink caffeinated beverages, might be advised to keep the amount to less than three daily drinks," Louis added by e-mail. "We did not find drinking one to two daily caffeinated beverages to increase the risk of miscarriage."
Scientists aren’t sure how caffeine contributes to miscarriages, but it’s possible it affects egg or sperm production, implantation of the fertilized egg, or the ability of the embryo to grow in the uterus.
To assess how lifestyle choices may influence miscarriage risk, Louis and colleagues followed 344 couples in Texas and Michigan through the first seven weeks of pregnancy. All of the couples recorded their daily use of cigarettes, caffeinated and alcoholic beverages, and multivitamins.
Overall, 98 women, or 28 percent, experienced a miscarriage during the study, as reported in the journal Fertility and Sterility.
Women 35 or older had nearly double the miscarriage risk of younger women, the study found. When women took daily multivitamins, their miscarriage risk was 55 percent lower than for their peers who didn’t do this.
The study wasn’t designed to prove that excessive caffeine consumption causes miscarriages, or that vitamins prevent pregnancy loss, the authors note.
It’s possible that women who cut back on caffeine did so because they were experiencing food aversions and vomiting—both signs of a healthy pregnancy–and this might explain some of the connection between miscarriages and caffeine, the researchers point out.
One surprise in the study is that researchers didn’t find an increased miscarriage risk associated with smoking or alcohol, however. This doesn’t mesh with previous research, noted Dr. Jeffrey Goldberg, a reproductive health researcher at Cleveland Clinic in Ohio who wasn’t involved in the study.
"This study did not address the fact that both smoking and alcohol use can reduce pregnancy rates and increase the risk of adverse effects on fetal development," Goldberg said by e-mail.
Doctors currently advise couples trying to conceive to avoid delays, especially when they’re over 35, and counsel women to limit caffeine and take multivitamins, Goldberg noted. Now, it seems men have something new to add to their to-do list.
"We would now have to recommend that the male partners also reduce their caffeine intake," Goldberg said.