Pre-pregnancy BMI, gestational weight gain trajectories, and new-onset hypertensive disorders in ART singleton pregnancies: a retrospective cohort study.

OBJECTIVE

To investigate non-linear associations between pre-pregnancy BMI and new-onset hypertensive disorders of pregnancy (HDP), and the relationship between gestational weight gain (GWG) trajectories and HDP.

METHODS

Using data from the Ningbo Birth Cohort of Population Undergoing ART (NBart) cohort (June 2018-June 2024), we included women with singleton ART pregnancies. Restricted cubic splines, latent class mixed models, and logistic regression were applied.

RESULTS

Of 4219 eligible pregnancies, 255 (6.0%) developed HDP. Risk increased when pre-pregnancy BMI exceeded 21.5 kg/m2 (∼6% higher per 0.5 kg/m2 gain). In stratified analyses, risk also increased below 16.6 kg/m2; the J-shaped relationship was evident in normal-weight women; a significant non-linear association was not detected within the overweight and obese subgroups alone. Advanced maternal age, nulliparity, primary infertility, and frozen embryo cycle amplified BMI-related risk. Exceeding recommended GWG guidelines at various pregnancy stages increased HDP risk; refined GWG thresholds were proposed for ART pregnancies. Two GWG patterns-concave negative (0-20 ± 1 weeks; aOR = 0.540, 95% CI: 0.290-0.944) and delayed acceleration (entire gestation period; aOR = 0.627, 95% CI: 0.380-0.996)-were inversely associated with HDP. Both featured minimal or negative early-pregnancy weight change followed by steady gain, occurred predominantly in overweight and obese women, and total GWG was lower compared with other patterns.

CONCLUSIONS

Maintaining optimal pre-pregnancy BMI and adhering to the proposed, more conservative GWG thresholds for ART pregnancies may reduce HDP risk. Distinct GWG trajectories may further modulate this risk.