Effect of pre-pregnancy body mass index on neonatal outcomes in women undergoing autologous frozen-thawed embryo transfer

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Authors:

Xiaoyan Yang, M.D., Beihong Zheng, M.S., Yun Wang, M.D. 

Abstract:

Objective

To investigate the associations between pre-pregnancy body mass index (BMI) and neonatal outcomes in women undergoing autologous frozen-thawed embryo transfer (FET).


Design

Retrospective cohort study.


Setting(s)

University-affiliated reproductive medical center.


Patient(s)

A total of 16,240 women with singleton deliveries achieved by autologous FET.


Intervention(s)

None.


Main Outcome Measure(s)

Neonatal outcomes included preterm birth (PTB), low birth weight (LBW), small-for-gestational age (SGA), large-for-gestational age (LGA), fetal macrosomia, and birth defects.


Result(s)

After adjusting for confounding factors, our study showed that in autologous FET cycles, the overweight women (23 kg/m2≤ BMI <27.5 kg/m2) were associated with increased rates of PTB (adjusted odds ratio [aOR], 1.226; 95% confidence interval [CI], 1.060–1.418), macrosomia (aOR, 1.692; 95% CI, 1.491-1.921), and LGA (aOR, 1.980; 95% CI, 1.715–2.286); and the obese women (BMI ≥27.5 kg/m2) were significantly associated with increased PTB (aOR, 1.503; 95% CI, 1.167–1.936), early PTB (aOR, 2.829; 95% CI, 1.679–4.765), very LBW (aOR, 3.087; 95% CI, 1.720–5.542), macrosomia (aOR, 2.325; 95% CI, 1.862–2.904), and LGA (aOR, 3.235; 95% CI, 2.561–4.085). The rate of SGA infants was higher in the underweight women (BMI <18.5 kg/m2) (aOR, 1.687; 95% CI, 1.375–2.071) than that in the normal-weight women (18.5 kg/m2≤ BMI ≤23 kg/m2). No significant difference was observed in the risk of birth defects between normal-weight cases and other BMI categories.


Conclusion(s)

Among women undergoing FET, pre-pregnancy BMI affected neonatal outcomes of singletons. BMI in Asian categories for overweight and obese showed significant increases in PTB, macrosomia, and LGA; early PTB and very LBW only increased in obese cases. In addition, underweight status was associated with increased risk of SGA. In contrast, there was no association between pre-pregnancy BMI and birth defects in FET cycles.

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.