Exploring maternal body mass index and perinatal health


Uncover the impact of maternal pre-pregnancy BMI on perinatal outcomes as elucidated by a multi-study investigation, shedding light on strategies to mitigate obstetric and neonatal risks through weight management.

Exploring maternal body mass index and perinatal health | Image Credit: © udra11 - © udra11 - stock.adobe.com.

Exploring maternal body mass index and perinatal health | Image Credit: © udra11 - © udra11 - stock.adobe.com.

Obstetrics and neonatal outcome risks are reduced by maintaining a healthy body mass index (BMI), according to a recent study published in BMC Medicine.


  1. Obesity affects a significant portion of women globally, with rates of 10% in low-income countries and 25% in high-income countries, underscoring the widespread nature of the issue.
  2. Increased maternal pre-pregnancy body mass index (BMI) is associated with a multitude of adverse perinatal outcomes, including gestational hypertension, preeclampsia, gestational diabetes mellitus, cesarean delivery, preterm birth, and neonatal complications.
  3. The study encompassed data from 446,526 women across 14 studies, aiming to comprehensively evaluate the impact of pre-pregnancy BMI on perinatal health outcomes.
  4. Results revealed a clear correlation between higher maternal BMI and increased risks of adverse pregnancy and perinatal outcomes, emphasizing the importance of weight management in maternal health.
  5. Maintaining a healthy BMI before pregnancy is highlighted as a crucial strategy to mitigate obstetric and neonatal complications, potentially reducing the incidence of adverse outcomes and improving maternal and child health.

Obesity impacts 10% of women residing in low-income countries and 25% residing in high-income countries. Multiple adverse perinatal outcomes including gestational hypertension (GH), preeclampsia (PE), gestational diabetes mellitus (GDM), pregnancy loss, cesarean delivery, preterm birth (PTB), perinatal depression, no breastfeeding initiation, and large for gestational age (LGA) are increased by increased maternal pre-pregnancy BMI.

While it is vital to understand the association between maternal pre-pregnancy BMI and perinatal health outcomes, most evidence on this association comes from observational studies. This indicates a need to better understand the role of BMI. Investigators conducted a study to evaluate the impact of pre-pregnancy BMI on perinatal health outcomes.

Data was obtained from 446,526 women across 14 studies. Participants included women with data on at least 1 assessed outcome, a singleton birth, delivery of an infant without a severe congenital anomaly, and European ancestry. Self-reported weight and height data was obtained to determine maternal BMI, measured as kg/m2.

In 8 studies, BMI data was collected before pregnancy, before 20 weeks’ gestation in 3, and between 24- and 32-weeks’ gestation in 1. Two studies did not have pre- or early pregnancy BMI data and were only used for Mendelian randomization analyses. Covariates included parity, maternal age, smoking during pregnancy, alcohol use during pregnancy, education, and offspring sex.

Outcomes evaluated included stillbirth, miscarriage, GH, PE, GDM, hypertensive disorders of pregnancies (HDP), perinatal depression, maternal anemia, pre-labor membrane rupture, induction of labor, PTB, LGA, small for gestational age (SGA), cesarean delivery, low birthweight, high birthweight, low Apgar score after 1 minute, low Apgar score after 5 minutes, neonatal intensive care unit (NICU) admission, and breastfeeding initiation.

Participants had a mean BMI of 23.0 to 28.5 kg/m2 and a mean maternal age of 25 to 31 years. Outcome incidence ranged from 107 for miscarriage to 78,472 for breastfeeding initiation.

Outcomes correlating with increased maternal BMI included stillbirth, miscarriage, HDP, GH, GDM, PE, induction of labor, pre-labor membrane rupture, caesarean section, high birthweight, LGA, PTB, low Apgar score at 1 minute, low Apgar score at 5 minutes, and NICU admission.

Outcomes negatively correlating with increased maternal BMI included maternal anemia, SGA infant, low birthweight, and breastfeeding initiation. An association was not reported between maternal BMI and perinatal depression.

Single nucleotide polymorphisms (SNPs) were evaluated during Mendelian randomization analyses. The R2 and mean F-statistic for the association of SNPs and BMI were 2.7% and 36, respectively.

These results indicated a correlation between increased maternal BMI and adverse pregnancy and perinatal outcome risks. Investigators concluded maintaining a healthy BMI can reduce the risk of obstetric and neonatal complications.


Borges MC, Clayton GL, Freathy RM, et al. Integrating multiple lines of evidence to assess the effects of maternal BMI on pregnancy and perinatal outcomes. BMC Med. 2024;22(32). doi:10.1186/s12916-023-03167-0

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