The association between pre-gravid and first trimester maternal weight and its implications for clinical research studies

Abstract

In clinical research, weight measurement in first trimester is often treated as a surrogate for pre-pregnancy weight. The validity of this critical assumption, however, is uncertain. Thus, we sought to prospectively evaluate the relationship between pre-gravid weight and first trimester weight. In this prospective preconception observational cohort study, 474 newly-married women in Liuyang, China, underwent pre-gravid evaluation at median 17.7 weeks before a singleton pregnancy, during which they had weight measurement in first trimester. The relationship between pre-gravid and first trimester weight was assessed by Bland–Altman analysis, Concordance Correlation Coefficient, and Pearson correlation. Mean pre-gravid weight was 49.8 ± 6.4 kg and mean weight in first trimester was 51.1 ± 7.0 kg. The Concordance Correlation Coefficient between pre-gravid and first trimester weight was 0.76 (95% limits of agreement: 0.72–0.80) and Pearson correlation was r = 0.78 (p < 0.0001), indicative of good concordance and correlation. As the timing of the weight measurement in first trimester increased in weekly increments from < 8 weeks to 14 weeks, the Concordance Correlation Coefficient ranged between 0.69 to 0.76 and the Pearson correlation ranged from 0.71 to 0.78 (all p < 0.0001). In conclusion, the observed concordance between pre-gravid weight and weight measured at any point in the first trimester provides a measure of validation for the widespread practice in clinical research of treating first trimester weight measurement as a surrogate for maternal weight before pregnancy.

Human Milk Composition Is Associated with Maternal Body Mass Index in a Cross-Sectional, Untargeted Metabolomics Analysis of Human Milk from Guatemalan Mothers

“…However, Retnakaran et al. [ 64 ] prospectively evaluated the relationship between pregravid weight and first trimester weight. The authors recognize that pregravid and first trimester weight measurements are unlikely to be identical due to modest physiological weight gain in the first trimester [ 64 ].…”

“…[ 64 ] prospectively evaluated the relationship between pregravid weight and first trimester weight. The authors recognize that pregravid and first trimester weight measurements are unlikely to be identical due to modest physiological weight gain in the first trimester [ 64 ]. However, there was good concordance between weight measurements suggesting that first trimester weight measurement can be a reasonable surrogate for pregravid weight, with the caveat that differences between these measurements are generally modest but can vary in magnitude [ 64 ].…”

“…The authors recognize that pregravid and first trimester weight measurements are unlikely to be identical due to modest physiological weight gain in the first trimester [ 64 ]. However, there was good concordance between weight measurements suggesting that first trimester weight measurement can be a reasonable surrogate for pregravid weight, with the caveat that differences between these measurements are generally modest but can vary in magnitude [ 64 ]. Although all mothers in this study sample were nursing at 6 mo postpartum, we did not collect additional information on infant feeding practices.…”

Pregnancy Outcomes in Women Who Developed Elevated Blood Pressure and Stage I Hypertension after 20 Weeks Gestation

“…26,27 Pre-pregnancy BMI was calculated from weight recorded at the first study visit, given that this measurement is a valid surrogate for prepregnancy BMI. 28 Finally, self-identified race and ethnicity were included as covariates because of the evident racial disparities in which there is an increased risk of morbidity and mortality associated with APOs, particularly in non-Hispanic Black women. [29][30][31] Results are reported as unadjusted (OR) and adjusted odds ratios (aOR) with corresponding 95% confidence intervals (CI).…”