Miscarriages are more common than most people realize, and often they are thought of as a woman’s issue. But, new research suggests sperm condition and a man’s endocrine function could be crucial factors in pregnancy health and viability.

A study conducted in Britain compared men whose partners had three or more subsequent miscarriages with men whose partners had not had problems with their pregnancies. Results showed significantly more men in the first group had impaired production of reproductive hormones. Their morning testosterone levels were lower than those of the other men. Morning is when men’s testosterone levels are at their highest.

These men also were more likely to have sperm that moved abnormally or were shaped oddly, and their sperm had higher levels of DNA-damaging free radicals — on average, four times as many free radicals. Not surprisingly, fragmented DNA also was more common.

Placenta formation relies greatly on DNA from the sperm. A developing baby gets its blood, oxygen and nutrient supply from the placenta. So, a poor-_quality placenta is just one way damaged sperm DNA could have an enormous effect on baby’s health in utero.

Abnormal blood vessel formation in the testicles or urinary tract infection are two other factors that may cause higher levels of free radicals, and bad DNA, in sperm.

Even after repeated miscarriages, the study authors note, it is not standard practice for physicians to evaluate the health of the father. They suggest that dad’s health should be examined too, along with the mother’s. After all, making a baby is a two-person production.