Clomid Birth Defect Link Investigated

< "">Clomid, a popular fertility drug, may increase the risk of birth defects. Until now, studies examining the association between Clomid and birth defects have been inconclusive, but new research just published online in the journal Human Reproduction has found a significant association with nine types of birth defects following use of Clomid.

Clomid is the brand name for the fertility drug clomiphene citrate. Clomiphene citrate may also be sold under the brand name Serophene. Clomid, the most commonly prescribed fertility drug, is used to induce ovulation (egg production) in women who do not produce ova (eggs) but who wish to become pregnant. Clomid is in a class of medications called ovulatory stimulants, according to the National Center for Biotechnology Information. The drug works similarly to estrogen, a female hormone that causes eggs to develop in the ovaries and be released.

To conduct this latest Clomid birth defects study, researchers with the U.S. Centers for Disease Control (CDC) used data from the National Birth Defects Prevention Study, a population-based, multi-site case–control study of major birth defects. Women from 10 U.S. regions with deliveries affected by at least one of 30 birth defects and mothers of live born infants without a major birth defect (controls) were interviewed. The women interviewed had delivered babies from October 1997 through December 2005. The exposure of interest involved reported Clomid use in the period from two months before conception through the first month of pregnancy. Women who conceived using assisted reproductive technology were excluded.

Thirty-six birth defect categories with at least three exposed cases were studied. Birth defects seen in the study included anencephaly (open cranium with absence of a brain), esophageal atresia (closed esophagus), omphalocele (protrusion of part of the intestine through the abdominal wall), craniosynostosis (premature fusion of the skull bones), three different types of heart defects, and a defect of the brain known as Dandy Walker malformation. The ninth defect (cloacal exstrophy) involves multiple abnormalities of the gastrointestinal and genitourinary tracts.

Twenty-two of the remaining 27 birth defect categories likewise showed an increased risk, ranging from 10 percent up to 170 percent after exposure to Clomid, although the study authors indicated that the numbers were insufficient to reach the scientific standard for “statistical significance.”

Though the researchers noted that the associations seen in this latest study should be interpreted cautiously, the research is not the first to point to possible links between birth defects and Clomid. For example, a 2003 study (Reefhuis, et. al) discovered a 280 percent increased risk of craniosynostosis; while another study published in 2006 (Wu, et al) revealed a 10-fold increased risk in being born with spina bifida. A separate 2006 article (Meijer, et al) found a 508 percent increased risk of penoscrotal hypospadias.

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