Inhibin A and inhibin B reflect ovarian function in assisted reproduction but are less useful at predicting outcome.

To test the hypothesis that dimeric inhibin A and/or inhibin B concentrations represent improved markers of in-vitro fertilization (IVF) outcome over follicle stimulating hormone (FSH), 78 women who achieved pregnancy within three assisted reproduction treatment cycles were matched to 78 women who underwent at least three assisted reproductive treatment cycles and failed to achieve pregnancy. Baseline serum inhibin B and FSH were obtained between days 1 and 4 in a cycle prior to ovarian stimulation, and inhibin A and B were measured immediately before the ovulatory stimulus and in follicular fluid from the lead follicle. Comparing pregnant and non-pregnant subjects at baseline, younger age (34.0 +/- 0.5 versus 36.0 +/- 0.5 years; P < 0.003) and a combination of FSH lower than the median value (11.2 IU/l) and inhibin B higher than the median value (76.5 pg/ml) were associated with pregnancy (P < 0.03), but FSH (11.7 +/- 0.5 versus 12.9 +/- 0.9 IU/ml) and inhibin B (89.0 +/- 10.2 versus 79.7 +/- 7.7 pg/ml) were not independently associated. At the time of the ovulatory stimulus, serum inhibin A (52.8 +/- 3.8 versus 40.0 +/- 2.7 IU/ml; P < 0.004), inhibin B (1623.8 +/- 165.1 versus 859.2 +/- 94.8 pg/ml; P < 0.0009) and the number of oocytes retrieved (14.6 +/- 0.8 versus 10.1 +/- 0.6; P < 0.0001) were predictive of pregnancy when controlled for age. Inhibin A was correlated with the number of embryos (r = 0.4; P < 0.0001). However, neither inhibin A nor inhibin B provided additional information in predicting successful outcome over age and number of oocytes. We conclude that: (i) in patients undergoing assisted reproductive technology, age and number of oocytes retrieved are the strongest predictors of success; (ii) of the parameters available prior to cycle initiation, a combination of lower FSH and higher inhibin B was associated with a greater chance for a successful outcome but an absolute cut-off could not be defined; and (iii) during ovarian stimulation, higher concentrations of inhibin A and inhibin B in serum are associated with successful IVF and mark ovarian reserve as a measure of oocyte number and quality.