Factors associated with monozygosity in assisted reproductive technology pregnancies and the risk of recurrence using linked cycles

Capsule:
The risk of monozygosity was higher with fresh day 5–6 embryos, donor oocytes, gonadotropin-releasing hormone agonist suppression, lower follicle-stimulating hormone doses, and assisted hatching (particularly day 2–3 embryos).

Authors:
Barbara Luke, Sc.D., M.P.H., Morton B. Brown, Ph.D., Ethan Wantman, M.B.A., Judy E. Stern, Ph.D.

Volume 101, Issue 3, Pages 683-689, March 2014

Abstract:

Objective:
To evaluate factors associated with monozygosity (MZ) (number of fetal heartbeats on early ultrasound greater than the number of embryos transferred) and the risk of recurrence in subsequent pregnancies using a national assisted reproduction database.

Design:
Historical cohort study.

Setting:
Clinic-based data.

Patient(s):
197,327 pregnancies (including 2,824 with evidence of MZ) from cycles reported to the Society for Assisted Reproductive Technology Clinic Outcome Reporting System (SART CORS) between 2004 and 2010.

Intervention(s):
None.

Main Outcome Measure(s):
Evidence of MZ, adjusted odds ratios and their 95% confidence intervals computed from logistic regression models.

Result(s):
In the univariate analysis, the risk of MZ was increased with ovulation disorders, donor oocytes, gonadotropin-releasing hormone agonist (GnRH-a) suppression, assisted hatching (AZH), and day 5–6 transfer, and was decreased with higher follicle-stimulating hormone (FSH) doses (≥3,000 IU). In the multivariate analysis, the risk of MZ was increased with GnRH-a suppression, AZH, and decreased with intracytoplasmic sperm injection (ICSI) and higher FSH dose. The interaction showed that although MZ was more likely with day 5–6 embryos, AZH had a minimal nonsignificant effect, whereas in day 2–3 embryos, AZH had a substantial statistically significant effect. Only one woman had a recurrence of MZ in a subsequent assisted reproduction pregnancy, which is consistent with randomness.

Conclusion(s):
The risk of MZ was higher with fresh day 5–6 embryos, donor oocytes, GnRH-a suppression, lower FSH doses, and AZH (particularly with day 2–3 embryos).

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