Parental preconception BMI and risk of adverse birth outcomes in 8 million parent–child triads: a nationwide population-based cohort study in China
Authors' conclusion
In this large, nationwide population-based cohort study, a preconception BMI in the category of underweight, overweight, or obesity in either or both parents was associated with a higher risk of various adverse birth outcomes, including perinatal death and birth defects. Therefore, maintaining a healthy weight for both parents before pregnancy is key to perinatal wellbeing.
Study context
- Population
- Parent–child triads with parental preconception BMI and birth outcome data, National Free Preconception Checkups Project, China, 2010–2020; mean age 26.18 (SD 4.33) years mothers, 27.83 (4.73) years fathers
- Participants
- 8,787,096 parent-child triads
- Exposure
- Parental preconception BMI categories vs healthy BMI in both parents
- Outcome
- Composite adverse birth outcome
Methodological detailsnationwide
- Nationwide
Main finding
As reported in the abstract
Each group vs both healthy BMIRelative risk (CI)
Maternal obesity, paternal healthy BMI
1.10(1.08–1.11)
Maternal healthy BMI, paternal obesity
1.04(1.04–1.05)
Both obesity
1.16(1.14–1.18)
Both underweight
1.08(1.06–1.09)
Observational data: associations, not effects.
Further findings
| Outcome | RR | |
|---|---|---|
| Perinatal deathBoth obesityvs Both healthy BMI | 1.17 (95% CI 1.03–1.33) | |
| Perinatal deathBoth underweightvs Both healthy BMI | 1.12 (95% CI 1.01–1.23) | |
| LGABoth obesityvs Both healthy BMI | 1.70 (CI 1.65–1.74) | |
| LGABoth underweightvs Both healthy BMI | 0.67 (CI 0.66–0.69) | |
| SGABoth obesityvs Both healthy BMI | 0.73 (CI 0.69–0.76) | |
| SGABoth underweightvs Both healthy BMI | 1.57 (CI 1.53–1.60) | |
| 0.512Relative risk (log scale) |
Large for gestational age (LGA)
- Monotonic positive association of maternal and paternal BMI with LGA risk (restricted cubic spline)
Small for gestational age (SGA)
- Monotonic inverse association of maternal and paternal BMI with SGA risk (restricted cubic spline)
Other adverse birth outcomes
- J-shaped associations of maternal and paternal BMI with all other adverse birth outcomes examined
Original publication
Parental preconception BMI and risk of adverse birth outcomes in 8 million parent–child triads: a nationwide population-based cohort study in China. Lancet Diabetes Endocrinol. Published 9 July 2025. doi:10.
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