The wheel of fortune: From egg to baby

Abstract

Objective: What is the chance of an egg to be a viable pregnancy? Is there a difference in the potential for a pregnancy between a drug-induced and a spontaneously ovulated egg? Do eggs generated through IVF have an inherent advantage over non-ART oocytes? Is the success of infertility treatment simply a function of the number of eggs in a given cycle or does the treatment itself grant certain advantages? Design: Retrospective cohort study. Materials and Methods: We studied 634 consecutive couples with primary or secondary infertility, who enrolled at the Center for Human Reproduction from January 1997. All couples were followed prospectively until their first pregnancy or for two years. There were 7 treatment modalities (surgery, AID, IUI, Clomid, gonadotropins, IVF, and no treatment). The total number of eggs and the number of viable pregnancies were recorded for each treatment modality. Eggs resulting in a pregnancy were divided into three categories: treatment- unrelated (>3 months from treatment or > 12 months from surgery), treatment-related (within the same cycle of treatment or <12 months from surgery, and indirectly-related (within 3 months of treatment). Survival analysis accounted for censored subjects (i.e. lost to follow-up). Statistical analysis included product-limit method, logrank test and T-test. 21 pair-wise comparisons were made between 7 treatment modalities. Significance was determined using chi-square at the Bonferroni corrected level of 0.002. Results: The product-limit graph showed no difference in the likelihood of an egg to become a viable pregnancy between the treatment, treatment-indirect and the non-treatment groups (p<0.2309). The number of eggs required to achieve 50% pregnancy rate is 18. In all but one of pair-wise comparisons there was no difference in the frequency viable pregnancies among the various treatment modalities. The only significant difference was found between Clomid and no treatment (p<0.000009). Conclusions: The likelihood of an egg to become a viable pregnancy is the same regardless of treatment. The only exception is Clomid-induced eggs compared to no treatment. The explanation for this finding is unclear. Overall, however, pregnancy frequency is directly related to the number of eggs rather than the treatment modality. It takes 18 eggs to produce a 50% pregnancy rate, regardless of treatment, whether it is the result of a single stimulated cycle or a year and a half of spontaneous ovulations.