Drinking more than two caffeinated beverages daily during preconception may affect couples' miscarriage risk, say researchers.
However, the study also found that women who took a multivitamin every day prior to conception and during early pregnancy were less likely to have a miscarriage than women who did not take a daily multivitamin.
First author Dr. Germaine Buck Louis, of the Eunice Kennedy Shriver National Institute of Child Health and Human Development at the National Institutes of Health (NIH), and colleagues publish their findings in the journal Fertility and Sterility.
Miscarriage is defined as a spontaneous fetal loss before 20 weeks' gestation. Among women who are aware they are pregnant, it is estimated that around 15-20 in every 100 will experience a miscarriage.
The risk of miscarriage increases with age, and women who have had previous miscarriages are at greater risk of having another.
Most miscarriages are caused by chromosome problems that affect fetal development, but infection, hormonal problems, drug and alcohol abuse, obesity, smoking and certain medical conditions can also raise the risk of miscarriage.
Now, the new study suggests caffeine consumption and use of multivitamins may also play a role in miscarriage risk.
Dr. Buck Louis and colleagues analyzed 2005-2009 data of 344 couples with a singleton pregnancy who were part of the Longitudinal Investigation of Fertility and the Environment (LIFE) study. Of these couples, 98 - or 28% - experienced a miscarriage.
The researchers assessed the lifestyle factors of each couple from the weeks before pregnancy up to 7 weeks' gestation, including cigarette use, consumption of alcoholic and caffeinated beverages and multivitamin use.
'Male partners matter, too'
The team found that couples' caffeine consumption was associated with miscarriage risk; female partners who consumed more than two caffeinated beverages daily prior to conception were 74% more likely to experience miscarriage than those who consumed less.
- The average American adult consumes around 300 mg of caffeine daily
- Coffee, soft drinks and tea remain the primary sources of caffeine
- American adults drink an average of three cups of coffee daily.
And they found the risk of miscarriage was just as strong when male partners consumed more than two caffeinated beverages a day in the weeks before conception; these men had a 73% greater risk, compared with those who drank less than two caffeinated beverages daily.
"Our findings also indicate that the male partner matters, too," says Dr. Buck Louis. "Male preconception consumption of caffeinated beverages was just as strongly associated with pregnancy loss as females."
The researchers note that previous studies have identified an increased risk of miscarriage with caffeine consumption in early pregnancy. However, they say such studies were unable to establish whether caffeine intake was a direct cause of miscarriage or an indicator of an unhealthy pregnancy.
They point out that expectant mothers often avoid certain foods and experience vomiting, which are usually signs of a healthy pregnancy. As such, women in these earlier studies may have given up caffeinated beverages, leading to results that show an increased risk of pregnancy loss with caffeine consumption.
However, Dr. Buck Louis and colleagues note that their study found that caffeine intake prior to pregnancy was linked to increased risk of miscarriage, which suggests a more direct association between consumption of caffeinated beverages during preconception and pregnancy loss.
Up to 79% lower miscarriage risk with daily multivitamin
The researchers also found that women aged 35 and older were at almost twice the risk of miscarriage than younger women.
Additionally, they found that women who took a daily multivitamin in the weeks prior to conception were at 55% lower risk for miscarriage, compared with women who did not take a daily multivitamin.
Women who continued to take a daily multivitamin in early pregnancy were found to be at 79% lower risk for miscarriage, according to the authors.
Commenting on the importance of their results, Dr. Buck Louis says:
"Our findings provide useful information for couples who are planning a pregnancy and who would like to minimize their risk for early pregnancy loss."
Speaking to Reuters, Dr. Buck Louis said their study does not suggest that couples trying to conceive should stop drinking caffeinated beverages. "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."
Last November, Medical News Today reported on a study suggesting moderate amounts of caffeine during pregnancy do not affect a baby's intelligence.