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Two-Dimensional Characterization of Maternal BMI and Height Associations With Pregnancy and Perinatal Outcomes After
Shuhei So1,2, Nao Murabayashi1,2, Wakasa Yamaguchi2
1Department of Reproductive and Perinatal Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan.
Aim:
To characterize maternal body mass index (BMI) and height as two nearly independent body-size dimensions in relation to pregnancy and perinatal outcomes after frozen-thawed embryo transfer (FET), and assess whether their joint evaluation reveals patterns not captured by BMI alone.
Methods:
In a single-center retrospective cohort of 10 059 FET cycles, dose-response relationships of BMI and height with 15 pregnancy-related outcomes were modeled using restricted cubic splines with modified Poisson regression and robust variance estimators. A joint additive model generated two-dimensional risk surfaces adjusted for maternal age, endometrial preparation, and obstetric covariates.
Results:
BMI was significantly associated with nine of 15 outcomes and height with seven. Two-dimensional risk maps showed outcome-specific patterns: hypertensive disorders of pregnancy were predominantly BMI-associated, whereas small-for-gestational-age and gestational diabetes reflected both dimensions, with higher risks in the low-BMI/short-stature and high-BMI/short-stature regions, respectively. Exploratory subgroup analyses by endometrial preparation method suggested possible heterogeneity for cesarean section, large-for-gestational-age, and miscarriage.
Conclusions:
Joint evaluation of BMI and height revealed heterogeneous body-size risk patterns-predominantly BMI-associated, height-associated, or combined-that BMI alone does not capture. Because height is readily available before pregnancy, considering it with BMI may refine body-size risk assessment after FET.