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No Deleterious Effect of IVF on Singleton Birth Weight and Pre-term Delivery Rate in Oocyte Donation Cycles for Either Infertile Recipients or Fertile Gestational Surrogates.

This research presented at the American Society for Reproductive Medicine (ASRM), Montreal, 2005.

CA Adams, J. Juanengo, N. Workman, L. Anderson, A. Scroop and SH Wood. Reproductive Sciences Center, La Jolla, CA, USA.

Objective: Several studies have reported an increased risk of low singleton birth weight and pre-term delivery following IVF as compared to spontaneous conceptions, but the reason(s) for this association are unclear. To examine whether factors related to a history of infertility are linked to this increased risk, we compared the obstetrical outcome of oocyte donation cycles in infertile women with those of fertile women acting as gestational surrogates. By examining only oocyte donation cycle recipients, we controlled for the possible effects of oocyte quality and eliminated any untoward effects of ovarian stimulation on the intrauterine environment.

Design: A retrospective analysis of data from consecutive oocyte donation cycles resulting in a viable pregnancy (high-order multiples excluded) performed over a 6-year period in a private IVF clinic.

Materials and Methods: Birth weights and gestational age at delivery were evaluated for 75 infertility patient (48 singletons and 27 twins) and 110 surrogate (60 singletons and 50 twins) deliveries. Pregnancies from fresh and frozen IVF/ICSI cycles were included. Potential confounding factors, including maternal age, BMI, and parity, were compared in the two groups, as was the rate of spontaneous fetal loss and the gender ratio. Statistical analyses were performed using the t-test or chi square as appropriate, with significance set at p < 0.05.

Results: As expected, the average maternal age (± SD) was lower for surrogates than infertility patients (32.2 ± 4.8 vs. 42.1 ± 3.5, respectively; p < 0.0001), and the BMI (27.3 ± 5.4 vs. 23.9 ± 3.6; p < 0.0001) and parity (3.4 ± 1.6 vs. 0.5 ± 0.9; p < 0.0001) were higher for surrogates than infertility patients. There was no significant difference between the two groups with regard to proportion of IVF versus ICSI (64% vs. 68% IVF), gender ratio (55% vs. 53% male) or percentage of pregnancies selectively reduced (10% vs. 10.7%, surrogates and infertility patients, respectively). There were no significant differences in singleton birth weight (3441 ± 629 vs. 3383 ± 525) or twin birth weight (2501 ± 664 vs. 2469 ± 631) and singleton gestational age (38.2 ± 2.3 vs. 38.9 ± 2.1) or twin gestational age (35.6 ± 2.9 vs. 35.6 ± 3.1) for surrogates and infertility patients respectively. A comparison of these birth weights to gestational age-specific regional and national data revealed that neither group was significantly different than median values for the general obstetrical population. The singleton pre-term delivery rate and percentage of small and large for gestational age infants in the two populations were also not statistically different.

Conclusions: When the potential effects of egg quality and of uterine effects resulting from ovarian stimulation are eliminated, the previously reported effects of IVF on birth weight and gestational age were no longer seen, irrespective of infertility history. This data, then, would suggest that any deleterious effects of IVF on these obstetrical outcomes result either from an effect of controlled ovarian stimulation on the intrauterine environment and/or from the reduced oocyte quality seen in many infertile patients.

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