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Updated: Sep 21, 2025
Assessment of Child Anthropometry in a Large Epidemiologic Study
Published on: February 2, 2017
Exploring comparative assessment of adiposity measures during pregnancy and postpartum
Atherai Maran1, Stephanie A Atkinson1, Valerie Bertram1
1Department of Pediatrics, McMaster University, Hamilton, Ontario, L8S 4L8, Canada.
Insights
Direct adiposity measures like bioelectrical impedance analysis (BIA) and skinfold thickness (SFT) are more sensitive than pre-pregnancy body mass index (pBMI) for identifying excessive adiposity in pregnant women. These direct measures can track changes throughout pregnancy and postpartum, offering better screening for at-risk pregnancies.
Area of Science:
- Reproductive Health
- Maternal-Fetal Medicine
- Body Composition Analysis
Background:
- Excessive adiposity during pregnancy is linked to adverse cardiometabolic and pregnancy outcomes.
- Pre-pregnancy body mass index (pBMI) is a common but potentially insensitive proxy for adiposity.
- Accurate, dynamic adiposity measurement during pregnancy is challenging.
Purpose of the Study:
- To evaluate longitudinal changes in body fat percentage (%BF) using skinfold thickness (SFT) and bioelectrical impedance analysis (BIA) during pregnancy and postpartum.
- To compare the discriminative power of SFT, BIA, and pBMI for identifying adiposity status.
- To assess the agreement of SFT and BIA with dual-energy X-ray absorptiometry (DXA) postpartum.
Main Methods:
- Longitudinal measurements of adiposity using BIA (%BF), SFT (sum and %BF), and pBMI in 181 pregnant women.
- Adiposity assessments at 12-17, 26-28, and 36-38 weeks gestation, with DXA at 6 months postpartum.
- Agreement assessed using Bland Altman plots, McNemar's test, and C-statistic for discrimination.
Main Results:
- Maternal adiposity significantly increased across pregnancy as measured by SFT sum and BIA %BF.
- Agreement between BIA and SFT for %BF was good in early pregnancy but decreased in late pregnancy, improving postpartum.
- BIA and SFT showed good agreement with DXA postpartum; pBMI identified fewer overweight/obese women compared to BIA and SFT.
Conclusions:
- pBMI is less sensitive than SFT and BIA in identifying excessive adiposity during pregnancy.
- Direct adiposity measures (%BF by BIA, SFT sum) can quantify changes and serve as clinical screening tools.
- Further validation of adiposity measurement techniques is recommended for mid and late pregnancy.
Background & Aims:
Excessive adiposity in pregnancy is associated with an altered cardiometabolic profile and adverse maternal and offspring outcomes. Pre-pregnancy body mass index (pBMI) is a proxy measure for adiposity that is most often used in clinical settings; however, it may not identify at-risk pregnancies caused by adiposity-related cardiometabolic dysfunction. The challenge is that validated direct adiposity measures are limited due to the dynamic nature of pregnancy. This exploratory analysis aimed to, 1) evaluate longitudinal changes in % body fat (BF) and the agreement between skinfold thickness (SFT) and bioelectrical impedance analysis (BIA) across pregnancy and in postpartum; 2) compare the discrimination power of SFT, BIA, and pBMI regarding adiposity status; and 3) assess agreement between SFT and BIA with dual-energy X-ray absorptiometry (DXA) in the postpartum.
Methods:
Participants enrolled in the Be Healthy in Pregnancy (BHIP) RCT (NCT01693510) had demographic data and pBMI collected at enrollment and adiposity measured at 12-17, 26-28, and 36-38 weeks gestation by BIA (%BF) and SFT (sum and %BF), and also by DXA at 6 months postpartum. Agreement between methods was assessed by Bland Altman plots and McNemar's test and C-statistic for discriminative power.
Results:
In 181 women with mean pBMI of 25.1 kg/m2 (min: 17.4 kg/m2, max: 39.6 kg/m2) and age 31.6 (SD: 4.0 yr), maternal adiposity increased significantly (p < 0.001) across pregnancy when measured by the sum of SFT or %BF by BIA, but not %BF by SFT. In early pregnancy, BF by BIA and SFT showed good agreement, with BIA values 1.8% greater than SFT, but low agreement in late pregnancy, with BIA values 7.1% greater than SFT. However, in the postpartum, agreement was similar to early pregnancy, and both BIA and SFT demonstrated good agreement with DXA. By pBMI, 45.5% of participants were categorized as overweight/obese, compared to 66.5% by BIA (p < 0.0001) and 54.5% by SFT (p < 0.0001).
Conclusions:
In comparison to SFT and BIA, the results suggest that pBMI is less sensitive in identifying participants with excessive adiposity, limiting its use as a screening tool for adiposity-related adverse outcomes in pregnancy. It would be preferable to use a direct measure of adiposity to screen for at-risk pregnancies. Both %BF by BIA and sum of SFT can quantify the change in adiposity across pregnancy and in the postpartum and thus could be adopted as clinical practice tools. Future research efforts should further refine and validate adiposity techniques for use, particularly in mid and late pregnancy.
Clinical Trial:
The BHIP clinical trial (NCT01693510). REGISTRATION SITE: https://clinicaltrials.gov/ct2/show/NCT01693510.
