Dads who had at least one alcoholic drink per week during the six months before they planned to get pregnant were 35 percent more likely to have a child with a birth defect, according to the study. Of the dads of kids born with birth defects, about 40 percent drank before conception, compared to 32 percent of the dads who fathered children without birth defects. Drinking increased the risk of birth defects such as congenital heart disease, cleft lips, and cleft palates, limb anomalies, digestive tract anomalies, defects in the brain, spine, and spinal cord, and even a condition in which the baby’s intestines poke through a hole next to their belly button. Men who drank had a particularly high risk of having a child with a cleft — 55 percent higher than sober dads. The way that a father’s drinking affects his children is likely through changes in his sperm. Because so many women drink in Western countries, it’s difficult to isolate the effects of dads-to-be who partake. But in China, only 3 percent of married women who plan to get pregnant drink alcohol, compared to about 33 percent of their husbands, which makes the country a perfect place to study this phenomenon. The researchers suggest that dads adjust their drinking habits before getting pregnant, but more research is needed to know how long before getting pregnant future fathers should stop drinking. Banyan Treatment Centers, a group of addiction treatment centers, recommends that dads abstain from alcohol for three months before conception.