The fertility drug clomiphene, sold as Clomid and Serophene, is an ovary stimulant designed to induce ovulation in women trying to conceive but who have irregular menstrual cycles, particularly those with polycystic ovarian syndrome.

However, the drugs have been associated with birth defects, fetal abnormalities and congenital malformations.

The Centers for Disease Control and Prevention published the findings of a National Birth Defects Prevention Study that took place between 1997 and 2005 that found mothers who reported using clomiphene citrate were more likely to give birth to children with birth defects such as anencephaly (baby born without parts of brain and skull), septal heart defects, coarctation of the aorta (narrowing of the aorta), esophageal atresia (baby born without part of the esophagus), craniosynostosis (premature fusion of an infant’s skull sutures) and omphalocele (baby’s abdominal organs are outside of the body).

Clomiphene citrate was also linked in small number of cases to Dandy-Walker malformation (congenital brain malformation), muscular ventricular septal defect and cloacal exstrophy (exposed abdominal organs).

In 2010, the Oxford Journal on Human Reproduction reported that 1.6 percent of pregnancies in the United States are conceived with the use of clomiphene citrate drugs such as Clomid and Serophene. That figure translates to some 67,000 exposed pregnancies per year.

The two types of birth defects most commonly reported to be associated with Clomid exposure in previous studies were neural tube defects and hypospadias (when the urinary opening in a baby boy is not on the head of the penis). The report notes that the association between clomiphene citrate drugs such as Clomid and these birth defects have been inconsistent.

According to the website Drugs.com, it is not known whether clomiphene passes into breast milk and risks harm to a nursing baby. The medication may slow breast milk production in some women.

Using clomiphene for longer than three treatment cycles may increase a woman’s risk of developing an ovarian tumor as well.

It is believed that after Clomid successfully fertilizes ovulation, it can remain in the mother’s system during the first weeks of pregnancy, potentially exposing the fetus to its dangerous side effects.

Clomid is classified by the U.S. Food and Drug Administration as a Category X drug, which means it is known to cause birth defects and animals or humans have developed fetal abnormalities in clinical research.

Category X drugs’ risks may outweigh the potential benefits and should be carefully discussed with a doctor before using.

Clomiphene dosage is typically a pill taken for one five-day cycle a month, which stimulates the production of hormones that trigger ovulation. Following a cycle of Clomid, the hypothalamus releases a hormone that messages the ovaries to release a mature egg or eggs into the fallopian tubes, which if fertilized with healthy sperm increases the chances of conception.