Live baby rate per oocyte with no stimulation

Abstract

What is the intrinsic fecundity rate of the human oocyte in relation to age? Ovarian hyperstimulation has been found to yield a live baby rate per oocyte of only about 4 to 6%. Thus on average more than 20 to 25 oocytes would be required to produce a single live baby. But this is in stimulated cycles. The live baby rate per egg in natural cycle single embryo transfer IVF would estimate better the intrinsic fertility of the human oocyte. 13,949 oocyte retrievals were performed in a natural cycle program with single embryo transfer in an attempt to determine what is the fertility potential of a single human oocyte that has not been submitted to ovarian hyperstimulation. Infertile women undergoing natural cycle with a single embryo transfer were studied retrospectively. The primary data of live baby per oocyte were approximated with a logistic curve r+1(a+exp[b(t-c)]) where r is live baby rate per oocyte and t is age in years. The coefficients were evaluated using gradient method as implemented in statistical package R (version 3.2.5). This allowed the construction of a robust logistic curve fit. The primary outcome of interest was live baby rate per oocyte. For women ≤42 years, the overall live baby rate per oocyte was 18%, which translated into only 5.5 oocytes needed to produce one baby. For women 42 years of age, every oocyte would have a 4% chance of becoming a baby, which means for a 42 year old woman it would require 22.7 rather than 5.5 eggs to produce a baby. The drop in intrinsic fertility per oocyte is summarized remarkably robustly in a logistic curve. There is at first a steady (almost horizontal) maintenance of fertility per oocyte (26%), followed after age 34 with a sharp linear decline until age 42 (4%), with a 10% loss of fertility every year. This decline slows down after age 43, with only 3% of original fertility remaining at age 45. The logistic model explains virtually all observed variation in live baby per oocyte rate: adjusted R-square is 99%. For all transfers the basic integrity of the logistic curve was remarkably robust. Live baby rate per single unstimulated oocyte is 26% until age 35, and then declines 10% per year until age 42, when it is only 4%. This is approximately a five times greater live baby rate per egg than has been reported with stimulated cycles.