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Bone, Jeffrey

University of British Columbia

Background: High pre-pregnancy body-mass-index (BMI) is an important risk factor for adverse maternal and perinatal outcomes. However, there are knowledge gaps regarding the association between high BMI and adverse birth outcomes, including the interrelationship between BMI and other risk factors for adverse pregnancy outcomes and how the risk associated with BMI may vary across gestational age. Methods: I used population-based data on live births and stillbirths from British Columbia, Canada (British Columbia Perinatal Database Registry, 2000-2022) and the United States (National Center for Health Statistics, 2016-2017). I examined whether earlier delivery explained the association between obesity and perinatal death. Possible heterogeneity in the association between BMI and adverse maternal and perinatal outcomes in women with chronic hypertension and diabetes mellitus, was quantified both overall and by gestational week. Further analyzed was the relationship between obesity and twinning, and adverse pregnancy outcomes in twin pregnancies. Results: The study population in British Columbia included live births and stillbirths to 524,845 women who delivered from 2000 to 2022. The prevalence of pre-pregnancy obesity among these women was 13%. Preterm delivery explained 63% of the association between obesity and the higher rates of perinatal death. Additionally, increasing pre-pregnancy BMI was associated with higher rates of twinning, which was partially explained by increased use of invitro fertilization. However, in contrast to singleton pregnancies, pre-pregnancy obesity was not associated with adverse pregnancy outcomes in twin pregnancies. Studies utilizing US data included 7,576,417 pregnancies, with a prevalence of pre-pregnancy obesity of 26.4%. Comorbid chronic hypertension or pre-pregnancy diabetes modified the relationship between obesity and adverse perinatal outcomes: obese women without these chronic conditions had a higher relative risk of adverse perinatal outcomes (compared with non-obese women), whereas this association was not present among obese women with chronic conditions. This effect modification was most evident between 26-35 weeks’ gestation. Conclusion: The strength of the relationship between pre-pregnancy BMI and adverse outcomes is attenuated in pregnancies complicated by other risk factors, such as chronic hypertension and diabetes, and twin pregnancy, and increases approaching term gestation. The pathophysiological underpinnings of these variations are likely complex and warrant further investigation.

Text

2024-12-23

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89984

Women+ and Children’s Health Sciences

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/