Mild or conventional ovarian stimulation for women with poor ovarian response?

This study compared mild ovarian stimulation (OS) to conventional OS for women with a poor ovarian response (POR) who were undergoing in vitro fertilization (IVF). It found that conventional OS resulted in more embryos, but the live birth rate after IVF was the same for both types of stimulation.

IVF is an infertility treatment in which eggs are removed from a woman, and the fertilized embryos are implanted in her uterus. The first step of IVF is to stimulate the ovaries to produce multiple eggs for collection. However, women with POR do not produce many eggs in response to ovarian stimulation.

Conventional controlled OS uses gonadotropin hormones. However, conventional OS can be expensive and difficult on the woman’s body. Mild OS uses oral medications such as letrozole (Femara). Letrozole blocks the body from producing the hormone estrogen. Low levels of estrogen cause the brain to release its own gonadotropin hormones. 

Previous studies have compared conventional to mild OS in women with POR. However, these have been small studies or have used patient records. Also, it is important to account for all embryos from an OS cycle, including those which are frozen. It is unclear how mild OS compares to conventional OS for women with POR.

This study included 191 women with POR who were undergoing IVF. 97 patients underwent mild OS using letrozole, and 94 underwent conventional OS. The two groups had similar ages and hormone levels. The patients were followed for two years.

On average, more eggs were retrieved for the conventional OS group (2 vs. 3). There were also significantly more fertilized embryos for the conventional OS group (1 vs. 2). However, fresh embryo transfers (FETs) more often resulted in an embryo implanting in the uterus for the mild OS group (27.27% vs. 21.70%).

The pregnancy rate per FET was similar in the mild OS group (37.50%) and the conventional OS group (32.79%). The live birth rate per FET was also similar in both groups (23.21 mild vs. 22.95% conventional). After accounting for all frozen embryos, the total per-patient birth rate was similar for both groups (19.59% mild vs. 18.09% conventional).

This study found that mild OS and conventional OS led to similar IVF birth rates for patients with POR. It also found that mild OS took a shorter period of stimulation and was less expensive.

Because this study took place at a single fertility center, it was difficult to recruit more patients with POR. Larger studies are needed.