Ovulation induction with minimal dose of follitropin alfa: a case series study

Gonadotropins are used in ovulation induction (OI) for patients with anovulatory infertility. Pharmacologic OI is associated with risks of ovarian hyperstimulation syndrome and multiple pregnancy. Treatment protocols that minimize these risks by promoting monofollicular development are required. A starting dose of 37.5 IU/day follitropin alfa has been used in OI, particularly among women at high risk of multifollicular development and multiple pregnancy. A retrospective case series study was performed to evaluate rates of monofollicular development and singleton pregnancy following standard treatment with 37.5 IU/day follitropin alfa.

Spanish centers that had performed at least five OI cycles during 2008 using 37.5 IU/day follitropin alfa as a starting dose were invited to participate. Data could be provided from any cycle performed in 2008 (up to a maximum of 12 consecutive cycles per site). Case report forms were collected during April-November 2009 and reviewed centrally. Descriptive statistics were obtained from all cases, and follicular development and clinical pregnancy rates assessed. Potential associations of age and body mass index with follicular development and clinical pregnancy were assessed using univariate correlation analyses.

Thirty centers provided data on 316 cycles of OI using a starting dose of 37.5 IU/day follitropin alfa. Polycystic ovary syndrome was the cause of anovulatory infertility in 217 (68.7%) cases. Follitropin alfa at 37.5 IU/day was sufficient to achieve ovarian stimulation in 230 (72.8%) cycles. A single follicle≥16 mm in diameter developed in 193 cycles (61.1%; 95% confidence interval [CI] 55.7-66.4%). Seventy-eight women (24.7%; 95% CI 19.9-29.5%) became pregnant: 94.9% singleton and 5.1% twin pregnancies. Fourteen started cycles (4.4%) were cancelled, mainly due to poor response. Univariate correlation analyses detected weak associations.

Monofollicular growth rate was comparable with optimal rates reported elsewhere and the pregnancy rate exceeded that in other studies of OI using gonadotropins. A starting dose of 37.5 IU/day follitropin alfa is an effective option in selected cases to prevent ovarian hyper-response without loss of efficacy. The analysis could not identify a single selection criterion for individuals who would benefit from this treatment approach; this merits further investigation in prospective studies.