Pregnancy may worsen or trigger obsessive compulsive disorder in some women.

Obsessive-compulsive disorder , or OCD, is an anxiety disorder in which people have persistent, unwanted thoughts that compel them to repeat routines and rituals over and over. An obsession with germs or cleanliness, for example, may drive a person to wash his or her hands constantly throughout the day. A few studies have found that OCD can also arise during or soon after pregnancy, and that pregnancy may worsen OCD symptoms in some women who already have the disorder.

To examine the impact of pregnancy, childbirth, and menstruation on OCD, researchers used medical records and interviews with 126 American women treated at the Yale OCD Clinic.

It was found that of the 78 women who had ever been pregnant, 24 (32 percent) had their first OCD symptoms during or soon after pregnancy. When the researchers looked at pregnancies among women with pre-existing OCD, it was found that the women's OCD symptoms worsened one-third of the time. In a smaller number of pregnancies (22 percent) symptoms actually improved.

It was also found that women whose pre-pregnancy OCD typically got worse in the premenstrual period were at greater risk of exacerbations during pregnancy. That finding supports the notion that there is a hormone-related subtype of OCD that affects some women.