Excess Weight Gain in First Trimester Impacts Fetal Growth
Excess weight gain in the first trimester impacts fetal fat distribution, potentially influencing long-term health.

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Researchers from the National Institutes of Health (NIH) have discovered that fetuses of individuals who gained excess weight during the first trimester of pregnancy may exhibit increased fat distribution in their upper arms and abdominal areas. These observations, published in the American Journal of Clinical Nutrition, suggest that early pregnancy weight gain may play a critical role in shaping fetal body composition, potentially influencing future health outcomes.
Study details and methods
The study analyzed data from over 2,600 singleton pregnancies, focusing on maternal weight before and during pregnancy. Up to five 3D ultrasound scans were used to assess fetal development. Excessive weight gain was defined as more than 2 kilograms (approximately 4.4 pounds) in the first trimester.
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Subscribe for FREEFetuses in the excessive weight gain group showed larger abdominal circumferences, abdominal areas and arm fat thickness compared to those in the adequate weight gain group. These differences persisted throughout pregnancy, even when second- and third-trimester weight gain remained within recommended limits.
This approach contrasts with prior studies that linked total pregnancy weight gain with birthweight. The use of 3D ultrasound allowed researchers to measure fetal fat distribution in detail during pregnancy, providing more nuanced insights.
Fetal fat distribution
This term refers to the way fat tissue is spread across different areas of the fetal body, such as the arms and abdomen. It is an indicator of growth and body composition that can provide clues about future health risks.
3D ultrasound
A medical imaging technique that provides detailed three-dimensional views of the fetus, allowing precise measurements of body parts, including fat layers.
Implications of timing in weight gain
The findings underscore the importance of timing in maternal weight gain. Instead of focusing solely on total weight gain across pregnancy, these results highlight the potential influence of first-trimester weight gain on fetal growth patterns. Such insights may inform strategies to optimize maternal and fetal health, aiming to reduce risks of obesity and related conditions later in life.
Reference: Wagner KA, Chen Z, Hinkle SN, et al. Relationship between gestational weight gain with fetal body composition and organ volumes in the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Fetal Dimensional Study: a prospective pregnancy cohort. Am J Clin Nut. 2025:S0002916524014333. doi: 10.1016/j.ajcnut.2024.12.007
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