WASHINGTON, United States (AFP) — Women have an increased risk of miscarriage if they or their partner consume more than two caffeinated drinks a day in the weeks leading up to conception, a new US study found.

Women who drink more than two caffeinated beverages per day during the first seven weeks of pregnancy were also more likely to have a miscarriage, according to the study published online last Thursday in the journal Fertility and Sterility.

But rates of miscarriage are reduced for women who take a daily multivitamin before and after conception.

The study, carried out by researchers from the National Institutes of Health (NIH) and Ohio State University, was based on data from the Longitudinal Investigation of Fertility and the Environment Study.

That study followed 501 couples in Michigan and Texas from 2005 to 2009, examining the relationship between fertility, lifestyle and exposure to chemicals in the environment.

The current study compared cigarette use, caffeinated beverage consumption and multivitamin use among 344 couples when the woman was carrying a single offspring. Of these pregnancies, 98 – or 28 per cent – ended in miscarriage.

The researchers’ conclusions were based on a statistical concept called ‘hazard ratio’, which estimates the chances of a particular outcome occurring during the study period.

A ratio greater than one indicates increased risk for miscarriage each day following conception, while a ratio less than one indicates reduced daily risk.

The risk of miscarriage was 1.74 when the woman consumed more than two caffeinated drinks a day, the study showed.

However, the risk was almost as high — 1.73 — if the male partner drank that much caffeine or more.

“Our findings also indicate that the male partner matters, too,” said lead author Germaine Buck Louis, director of the Division of Intramural Population Health Research at the NIH. “Male preconception consumption of caffeinated beverages was just as strongly associated with pregnancy loss as females.”

The study also found that taking a daily multivitamin significantly reduced chances of miscarriage.

Taking a vitamin in the weeks leading up to conception had a hazard ratio of 0.45, a 55 per cent reduction in risk for pregnancy loss.

Women who continued to take multivitamins through the early stages of pregnancy had a hazard ratio of 0.21, a risk reduction of 79 per cent.