Predictive Value and Clinical Impact of Basal Follicle-Stimulating Hormone in Subfertile, Ovulatory Women

Abstract

It is expected that, as women continue to postpone childbearing, more of them will present to fertility centers with age-related subfertility. The most widely used measure of ovarian reserve is the basal blood level of follicle-stimulating hormone (FSH) in the early follicular phase of the cycle. Its predictive value seems limited in the setting of in vitro fertilization, and its value for screening a general subfertile population is not clear. This prospective cohort study, carried out at 19 fertility centers in the Netherlands, enrolled subfertile ovulatory women lacking 2-sided tubal pathology whose partners had normal sperm parameters. The fertility workup included an estimate of basal FSH on cycle day 3. The study population consisted of 3270 consecutive couples followed up at 12 months, 562 of whom (16%) had a spontaneous ongoing pregnancy. Four of these were multiple pregnancies. Another 61 couples had unsuccessful pregnancies. A basal FSH of 8 IU/L or higher was associated with a reduced likelihood of spontaneous ongoing pregnancy. The hazard ratio was 0.93, with a 95% confidence interval of 0.87–0.98. On multivariable analysis, female age, cycle length, and an FSH level of 8 IU/L or higher were strong negative predictors for spontaneous ongoing pregnancy. In analyzing 3219 couples, adding FSH to a prediction model based on female age, duration of subfertility, previous pregnancy, referral status, and semen analysis altered the likelihood of conceiving spontaneously from 30% or more to less than 30%. Compared with women whose basal FSH was less than 8 IU/L, the probability of conceiving was reduced 40% if the basal FSH was 15 IU/L, and 58% if it was 20 IU/L. A basal FSH level of 8 IU/L or higher was associated with decreased fecundity in ovulatory women in this study, independently of female age and cycle length. This finding does not, however, often lead to altered management, and for this reason the investigators do not recommend routinely estimating basal FSH in subfertile couples.