Objective: To explore the relationship between couples' prepregnancy body mass index (BMI) and time to pregnancy (TTP) among those with no prior gravidity.
Design: Retrospective cohort study.
Setting: Local maternal/child health care or family-planning service institutions.
Patient(s): A total of 2,301,782 eligible couples participating in the National Free Preconception Check-up Projects from January 1, 2015 to December 31, 2017.
Intervention(s): None.
Main outcome measure(s): Time to pregnancy.
Result(s): Underweight, overweight, or obese status in women and underweight status in men were associated with couples' prolonged TTP. The optimal BMI levels were 20.61-23.06 kg/m2 and 22.69-27.74 kg/m2 for women and men, respectively. Compared with couples in whom both partners had a normal BMI, the pregnancy rates were reduced by 10% (fecundability odds ratio [FOR] 0.90; 95% confidence interval [CI], 0.88-0.92) and 19% (FOR 0.81; 95% CI, 0.78-0.84) for couples in whom both partners were underweight or obese, respectively. The combination of women with a normal BMI and overweight men had the greatest fertility (FOR 1.03; 95% CI, 1.02-1.03), and the combination of obese women and underweight men had the lowest fertility (FOR 0.70; 95% CI, 0.65-0.76).
Conclusion(s): Abnormal prepregnancy BMIs in either women or men were associated with prolonged TTP among couples with no prior gravidity. Scientific management of couples' prepregnancy BMI could improve their fertility.
Keywords: Body mass index; fertility; prepregnancy; prospective study; time to pregnancy.
Copyright © 2020 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.