Obstetric and perinatal outcomes after either fresh or thawed frozen embryo transfer: an analysis of 112,432 singleton pregnancies recorded in the Human Fertilisation and Embryology Authority anonymized dataset

Frozen embryo transfers are associated with a lower risk of low and very low birth weight, but a higher risk of high birth weight.

Like Comment

Volume 106, Issue 7, Pages 1703-1708

Authors:

Abha Maheshwari, M.D., Edwin Amalraj Raja, Ph.D., Siladitya Bhattacharya, M.D.

Abstract:

Objective

To explore obstetric and perinatal outcomes in singleton pregnancies occurring as a result of fresh and thawed frozen embryo transfer using anonymized Human Fertilisation and Embryology Authority data.

Design

Retrospective cohort study.

Setting

Not applicable.

Patient(s)

Singleton births after IVF/intracytoplasmic sperm injection cycles in the United Kingdom (1991–2011).

Intervention(s)

A total of 112,432 cycles (95,911 fresh and 16,521 frozen) were analyzed using multivariate logistic regression to explore associations between type of embryo transferred (frozen vs. fresh) and obstetric and perinatal outcomes. Relative risks (RRs) and their 99.5% confidence intervals (CIs) were calculated using Stata 14 MP, adjusting for potential confounders.

Main Outcome Measure(s)

Birth weight.

Result(s)

The adjusted RR (99.5% CI) of low birth weight [0.73 (0.66–0.80)] and very low birth weight [0.78 (0.63–0.96)] were all lower after frozen embryo transfer; however, RR of having a high birth weight baby was higher [1.64 (1.53–1.76)]. There was no difference in RR of preterm birth [0.96 (0.88–1.03)], very preterm birth [0.86 (0.70–1.05)], and congenital anomalies [0.86 (0.73–1.01)].

Conclusion(s)

The findings of low birth and very low birth weight after thawed frozen embryo transfer are consistent with the literature and provide reassurance regarding the outcome of pregnancies after frozen embryo transfers. However, they highlight the possibility of high birth weight in these babies. Because these results are based on observational data, further evidence from randomized, controlled trials is needed before elective cryopreservation of all embryos is practiced in preference to the current practice of transfer of fresh embryos.


Read the full text here.

Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders. The journal publishes juried original scientific articles in clinical and laboratory research relevant to reproductive endocrinology, urology, andrology, physiology, immunology, genetics, contraception, and menopause. Fertility and Sterility® encourages and supports meaningful basic and clinical research, and facilitates and promotes excellence in professional education, in the field of reproductive medicine.

No comments yet.