The process of in vitro fertilization (IVF) is complex and works best when it addresses the unique medical situation of the couple in question. The basic procedures remain the same but the details need customization in some cases. A recent study suggests that customization may lead to greater success when the dosage of some IVF medications are adjusted to the weight of the woman.

The US Centers for Disease Control and Prevention (CDC) report that more than 1% of all babies born in the US each year are conceived by assisted reproductive technologies (ART), including IVF. That number is expected to rise as more women delay motherhood into their 30s and 40s and as the success rate of IVF continues to rise as well.

Researchers at the University of Colorado at Denver led by Dr. Nannette Santoro have discovered IVF success rate can be improved if the individual woman's weight is taken into consideration when calculating the dosage of ovulation-stimulating hormones. Typically, women who are overweight or obese experience a lower rate of success than women of healthy weight. The Santoro team increased the rate of success by tweaking the dosage of certain IVF medications.

To test their theory, the Santoro team measured the absorption rate over a 14-hour period of a specific medication in 10 obese women and in 10 women of normal weight. The drug under study is a GnRH antagonist important in the early part of the IVF cycle.

Women have prescribed a GnRH antagonist before eggs are harvested for IVF. The drug delays ovulation until enough healthy eggs are produced to make harvest feasible.

During the study, the women were each given the standard dose of GnRH antagonist and its rate of absorption was measured using blood tests. Blood tests started eight hours after the drug was administered and continued for six hours during which frequent blood tests were done.

In the 10 obese women, the GnRH antagonist was cleared from their bloodstreams more quickly than happened with the women of normal weight, making them more likely to begin ovulation before the egg harvest reached the desired stage of development. To further complicate the issue, half of the obese women experienced a release of luteinizing hormone during the 14-hour study period. Luteinizing hormone signals the body that it's time to release eggs from the ovaries.

Santoro says her study indicates the need to consider personalized dosing regimens for IVF patients with weight issues or different medications altogether. “Given the cost of IVF and stress of infertility, it is important to maximize each woman’s chances of conceiving a child,” she said.

A full report of the Santoro study will be published in the May 2014 issue of the Journal of Clinical Endocrinology & Metabolism.

Source: "Standard IVF Medication Dose Less Effective in Obese Women." Endocrine Society/ Current Press Releases. Endocrine Society. n.d. Web. Mar 31, 2014.