Variation in urine osmolality throughout pregnancy: a longitudinal, randomized-control trial among women with overweight and obesity

• Published in: European journal of nutrition Vol. 61; no. 1; pp. 127 - 140
• Main Authors: Rosinger, Asher Y., Bethancourt, Hilary J., Pauley, Abigail M., Latona, Celine, John, Jason, Kelyman, Alysha, Leonard, Krista S., Hohman, Emily E., McNitt, Katherine, Gernand, Alison D., Downs, Danielle Symons, Savage, Jennifer S.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-02-2022; Springer Nature B.V
• Subjects: Age; Behavior modification; Birth weight; Body weight; Body weight gain; Chemistry; Chemistry and Materials Science; Female; Fetuses; Gestational age; Gestational Weight Gain; Humans; Hydration; NCT; NCT03945266; Nutrition; Obesity; Obesity - therapy; Original Contribution; Osmolar Concentration; Overweight; Physical activity; Pregnancy; Pregnancy Complications; Regression analysis; Retrospective Studies; Water intake; Womens health; Pregnancy; Water intake; Urine osmolality; Birth outcomes; DOHaD; Hydration
• ISSN: 1436-6207; 1436-6215
• DOI: 10.1007/s00394-021-02616-x

Purpose
Water needs increase during pregnancy, and proper hydration is critical for maternal and fetal health. This study characterized weekly hydration status changes throughout pregnancy and examined change in response to a randomized, behavioral intervention. An exploratory analysis tested how underhydration during pregnancy was associated with birth outcomes.
Methods
The Healthy Mom Zone Study is a longitudinal, randomized-control trial intervention aiming to regulate gestational weight gain (GWG) in pregnant women with overweight/obesity (
n
 = 27). Fourteen women received standard of care; 13 women additionally received weekly guidance on nutrition, physical activity, water intake, and health-promoting behaviors. Hydration status was measured weekly via overnight urine osmolality (Uosm) from ~ 8–36 weeks gestation; underhydration was dichotomized (Uosm ≥ 500 mOsm/kg). Gestational age- and sex-standardized birth weight and length
z
scores and percentiles were calculated. We used mixed-effect and linear regression models to test covariate-adjusted relationships.
Results
No differences existed in Uosm or other characteristics between control and intervention women at baseline. Significant interactions (
p
 = 0.01) between intervention and week of pregnancy on Uosm indicated intervention women maintained lower Uosm, whereas control women had a significant quadratic (inverse-U) relationship and greater Uosm in the second and early third trimesters. Results were consistent across robustness and sensitivity checks. Exploratory analyses suggest underhydration was associated with birth weight, but not length, in opposite ways in the second vs. third trimester.
Conclusion
A multi-component behavioral intervention helped women with overweight/obesity maintain better hydration throughout pregnancy. Future studies should confirm birth outcome results as they have important implications for early life nutrition.
Trial registration
ClinicalTrials.gov Identifier: NCT03945266; registered May 10, 2019 retrospectively.