If you're pregnant and you've got a headache or a sore muscle, you may just have to tough it out. A new Danish study has found that the use of mild painkillers during pregnancy may raise the risk of undescended testicles in male babies, a condition linked to infertility and cancer in later life.

The study found that the use of drugs such as acetaminophen, aspirin and ibuprofen during pregnancy may partly account for a sharp increase in male reproductive disorders in recent decades. The research, published in the journal Human Reproduction, found that women who took a combination of more than one mild analgesic during pregnancy had an increased risk of giving birth to sons with undescended testicles, a condition known as cryptorchidism. Cryptorchidism is a known risk factor for poor semen quality and testicular cancer.

In the study, researchers from Finland, Denmark and France looked at two groups of women, 834 in Denmark and 1,463 in Finland. The women were questioned about their use of medication during pregnancy. In the second phase of the study, researchers examined the male babies of the women in the study at birth looking for any signs of cryptorchidism.

They found those women who used more than one painkiller simultaneously, such as acetaminophen and ibuprofen, had a seven-fold increased risk of giving birth to sons with some form of cryptorchidism compared to women who took nothing. The most sensitive time period for reaction appeared to be the second trimester of pregnancy.

The researchers suspect that painkillers upset the natural balance of male hormones at work in unborn baby boys and this hinders normal development. Studies of rats back this theory.

More than half of pregnant women in the U.S. report taking mild painkillers. Could this be the reason that research in developed nations has shown that sperm counts have fallen by about 50 percent in the past half century?

Researchers are hoping to do more studies to clarify the link. In the meantime, they suggest that women seek advice from their obstetrician or midwife if they are concerned about which medications to take during pregnancy.

The opinions expressed by MNN Bloggers and those providing comments are theirs alone, and do not reflect the opinions of MNN.com. While we have reviewed their content to make sure it complies with our Terms and Conditions, MNN is not responsible for the accuracy of any of their information.