Key Findings: Use of clomiphene citrate and birth defects, National Birth Defects Prevention Study, 1997-2005

The journal, Human Reproduction, has published a new CDC study: “Use of clomiphene citrate and birth defects, National Birth Defects Prevention Study, 1997–2005.” You can read the abstract of the article here. The findings from this article are summarized below.

About this study:

This study used data from the National Birth Defects Prevention Study, a population-based, case-control study of major birth defects in the United States. Population-based means that the study looked at all babies with birth defects whose mothers live in the study region, which is important to make sure that study results apply to the U.S. population in general. Researchers wanted to see if there was a link between using clomiphene citrate and the occurrence of certain birth defects. Women who became pregnant by using assisted reproductive technologies, including in-vitro fertilization or IVF, were not included in this study.

A summary of the findings can be found below. The findings should be interpreted with caution because they are based on small numbers of women who used clomiphene citrate. Also, it is difficult to determine whether the findings are due to the use of the clomiphene citrate or because these women had difficulty getting pregnant due to some underlying conditions that affected fertility.

Main findings from this study include:

• Mothers of children with the following birth defects said they used clomiphene citrate more often than mothers of children without birth defects:
  • Anencephaly
  • Septal heart defects
  • Coarctation of the aorta
  • Esophageal atresia
  • Craniosynostosis
  • Omphalocele
• Clomiphene citrate was also linked (in a very small number of cases) with the following birth defects:
  • Dandy-Walker malformation
  • Muscular ventricular septal defect
  • Cloacal exstrophy

Some of these links with specific birth defects were observed for the first time. For example, the links between clomiphene citrate and Dandy-Walker malformation, coarctation of the aorta, esophageal atresia, and omphalocele have not been observed in previous studies. More studies are needed to understand if there is a link between birth defects and clomiphene citrate. Further studies are also needed to determine whether the findings are due to the use of the clomiphene citrate, or because these women had difficulty getting pregnant due to some underlying conditions that affected fertility.

More Information

For more information about birth defects, please visit the CDC’s birth defects webpage.

Reference

Reefhuis J, Honein MA, Schieve LA, Rasmussen SA, and the National Birth Defects Prevention Study. Use of clomiphene citrate and birth defects, National Birth Defects Prevention Study, 1997–2005. Hum Reprod. 2010 Nov 29. [Epub ahead of print]