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Cosmos Study

Reduction in Mother’s BMI After Pregnancy Linked to Lower Likelihood of Obesity for Her Child

March 5, 2024
Dual-Team Study
Team A:Kersten Bartelt, RNAlex Piff
Team B:Karen Wong, MDNeil Sandberg

Key Findings

  • Children born to mothers who were obese or overweight before pregnancy and who maintain that BMI category after pregnancy have a significantly higher likelihood of being obese compared with children born to mothers who were not overweight both before and after pregnancy. Children born to mothers who were obese and remain obese are 146% more likely to become obese and 83% more likely to be obese if they were born to mothers who were overweight and remain overweight.
  • However, if the child’s mother decreases her BMI category from obese before pregnancy to overweight after pregnancy, the likelihood of the child being obese is reduced by 51 percentage points. Similarly, if the child’s mother decreases her BMI category from overweight before pregnancy to not overweight after pregnancy, the likelihood of the child being obese is reduced by 8 percentage points.
  • While BMI reduction after pregnancy is correlated with a reduced likelihood of obesity in the child, the mother’s BMI before pregnancy is still more closely correlated with the child’s likelihood of being obese.

Childhood obesity is correlated with an increased risk of chronic conditions later in life such as hypertension, hyperlipidemia, diabetes, and others.1 Previous studies have established a correlation between maternal BMI before pregnancy and the child’s risk of obesity, but less is known about whether postpartum BMI changes can influence that risk.2,3,4

To assess whether a change in maternal BMI influences the likelihood of obesity in her child, we studied the change in maternal BMI category from before pregnancy to at least six months after pregnancy and whether the child reached an obese BMI category after the age of two. We adjusted for the mother’s history of type 2 diabetes, age, race, BMI category before pregnancy, and social vulnerability. We also adjusted for gestational age at birth and sex of the child. Childhood obesity was defined as a BMI greater than the 95th percentile for the child’s sex and age. Maternal obesity was defined as a BMI greater than 30, overweight was defined as a BMI between 25 and 30, and not overweight was defined as a BMI under 25.

We found that children born to mothers classified as obese both before and after pregnancy have a 146% increased likelihood of being obese compared to children born to mothers classified as not overweight both before and after pregnancy. However, for children born to mothers who are obese before pregnancy and overweight after pregnancy, the likelihood is reduced by 51 percentage points, to 95%. Similarly, children born to mothers classified as overweight before and after pregnancy have a 53% increased likelihood of being obese, but if the mother is not overweight after pregnancy, the child’s likelihood of obesity is reduced by eight percentage points, to 45%.

Figure 1
Relative Change in Likelihood of Childhood Obesity by Change in Maternal BMI After Pregnancy
Relative Change in Likelihood of Childhood Obesity by Change in Maternal BMI After Pregnancy
Figure 1. The relative likelihood of a child being classified as obese by change in maternal post-pregnancy BMI category.

We also looked at the relationship between childhood obesity and a mother gaining weight at least six months after pregnancy, leading to an increased BMI category. We found that the child’s likelihood of being obese increased by 33 and 30 percentage points when their mother went from not overweight to overweight or from overweight to obese, respectively.

Although there is a correlation between BMI reduction after pregnancy and a decreased risk of obesity in the child, it is important to note that the mother’s BMI prior to pregnancy remains a stronger predictor of the child’s likelihood of obesity.

These data come from Cosmos, a collaboration of 239 Epic health systems representing more than 238 million patient records from 1,345 hospitals and more than 28,000 clinics from all 50 states and Lebanon. This study was completed by two teams that worked independently, each composed of a clinician and research scientists. The two teams came to similar conclusions. Graphics by Mark LeBay.

References

  1. Reduce the proportion of children and adolescents with obesity — NWS‑04. Health.gov. Reduce the proportion of children and adolescents with obesity — NWS‑04 – Healthy People 2030 | health.gov. Accessed February 28, 2024.
  2. Voerman E, Santos S, Patro Golab B, Amiano P, Ballester F, Barros H, et al. (2019) Maternal body mass index, gestational weight gain, and the risk of overweight and obesity across childhood: An individual participant data meta-analysis. PLoS Med 16(2): e1002744. https://doi.org/10.1371/journal.pmed.1002744
  3. Liao XP, Yu Y, Marc I, et al. Prenatal determinants of childhood obesity: a review of risk factors. Can J Physiol Pharmacol. 2019;97(3):147-154. doi:10.1139/cjpp-2018-0403
  4. Mannino A, Sarapis K, Moschonis G. The Effect of Maternal Overweight and Obesity Pre-Pregnancy and During Childhood in the Development of Obesity in Children and Adolescents: A Systematic Literature Review. Nutrients. 2022; 14(23):5125. https://doi.org/10.3390/nu14235125