Comparative analysis of fetal and neonatal outcomes of pregnancies from fresh and cryopreserved thawed oocytes in the same group of patients

Capsule:
This is an analysis of fetal and neonatal outcomes from fresh and thawed oocyte cycles in the same group of 855 patients.

Authors:
Paolo Emanuele Levi Setti, M.D., Elena Albani, B.Sc., Emanuela Morenghi, Ph.D., Giovanna Morreale, Luisa Delle Piane, M.D., Giulia Scaravelli, Ph.D., Pasquale Patrizio, M.D., M.B.E., H.C.L.D.

Volume 100, Issue 2, Pages 396-401, August 2013

Abstract:

Objective:
To analyze the fetal and neonatal outcomes of pregnancies achieved with fresh and/or frozen oocytes in the same group of patients.

Design:
Observational study and comparative analysis.

Setting:
Research unit of an academic medical center.

Patient(s):
A group of 855 women with cryopreserved oocytes and their resulting 954 assisted reproductive technology clinical pregnancies were enrolled and followed up during the same time period and in the same clinical setting; the outcomes of 197 pregnancies from frozen/thawed oocytes were compared with 757 obtained from fresh sibling oocyte cycles.

Intervention(s):
None.

Main Outcome Measure(s):
Pregnancies were followed until delivery, and neonatal data (up to 28 days after delivery) were collected.

Result(s):
No significant differences were found between the use of fresh and frozen oocytes in the rates of therapeutic abortions for fetal anomaly (1.5% vs. 0.8%) and ectopic pregnancies (3.6% vs. 2.9%), but a significantly higher rate of spontaneous abortions at ≤12 weeks (17.6% vs. 26.9%) was observed in the frozen/thawed oocytes group. No statistical differences were found in major anomalies at birth (2.8% vs. 4.6%). Despite no difference in gestational age at delivery, the mean birth weights were significantly lower with fresh oocyte pregnancies, both in singleton (2,725 ± 727 g) and twins (2,128 ± 555 g), than with frozen–thawed oocytes (3,231 ± 615 g and 2,418 ± 492 g, respectively). However, the analysis of the 63 patients who obtained pregnancies both in fresh and thawed cycles (138 pregnancies) showed no differences in the abortion rate and in the mean birth weight.

Conclusion(s):
These results provide strong support to the notion that fetal and perinatal complications and congenital anomalies do not differ between pregnancies from frozen–thawed and fresh oocytes. The significantly lower mean birth weight observed with pregnancies from fresh oocytes supports similar observations reported for pregnancies from embryo cryopreservation and requires further prospective studies.

  • Amanda N. Kallen

    The authors present a large single-center analysis of obstetric outcomes after use of fresh vs cryo-thawed oocytes. The study is interesting, the size of comparison groups impressive, and the results overall reassuring to patients. Notably, the authors state that there are no statistically significant differences between the two in terms of congenital anomalies, but I would have liked to see the statistical analyses for individual congenital anomalies between the two groups. Were these analyses done?

  • Lauren Johnson

    This retrospective cohort study adds to the growing body of literature suggesting that oocyte cryopreservation is a safe practice. The authors found no difference in the rate of major congenital anomalies among infants conceived using fresh vs. cryopreserved oocytes. It is important to note that the cryopreserved oocytes in this cohort were slow-frozen, and therefore, the data cannot be extrapolated to vitrified oocytes. Also, the study was likely underpowered to detect a difference in congenital anomalies; nonetheless, it is critical that authors report these results so that they may inform further research and be utilized in meta-analyses.

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