(P10-065-24) Examining Correlations Between Plasma Volume, Hydration, and Anemia Biomarkers in Pregnant Women in Tanzania

Objectives: Plasma volume (PV) expands by about 50% across pregnancy as a physiological adaptation to transport nutrients to the developing fetus. Little research has been conducted to estimate changes in PV across pregnancy in low-resource settings. We aimed to estimate PV in late pregnancy and examine relationships with nutrition-related biomarkers.

Methods: In a vitamin B12 supplementation trial in Tanzania, pregnant women (n = 40) were enrolled at 25-28 weeks gestation for a 4-week in-patient clinic stay. On days 1 and 22, maternal anthropometry and blood pressure were measured, and urine specific gravity (USG) was assessed using a pen refractometer. Hemoglobin (Hb) and hematocrit (Hct) were measured by a complete blood count; we used Hb to classify anemia ( < 11.0 mg/dL). We estimated PV with the Smith-Yarbrough equation: PV = 673 + (32.9*gestational age) + (1857.2*body surface area). We examined correlations between PV, hydration, Hb, Hct, and blood pressure using Spearman’s rank correlation.

Results: Participants had a mean age of 28.9 ± 6.0 years, mean height of 157 ± 7 cm, mean mid upper arm circumference of 27 ± 3 cm, were predominantly married, and had primary or secondary education. PV estimations were 3,819 ± 304 mL and 3,862 ± 297 mL on days 1 and 22, respectively, an increase of 1.1%. The prevalence of anemia was 90.0% and 92.5% at days 1 and 22, respectively, and 95% of participants were hydrated (95% for both days). PV on day 1 was strongly positively correlated with PV on day 22 (r=0.99, p< 0.01). PV was also positively correlated with Hb and Hct on day 1 (Hb: r=0.48, p< 0.01; Hct: r=0.40, p=0.01) and day 22 (Hb: r=0.47, p< 0.01; Hct: r=0.43, p< 0.01). Correlations were between 0 and 0.3 (all with p >0.05) for PV, blood pressure, and USG.

Conclusions: In late pregnancy in Tanzania, we found correlations between PV and HGB and HCT, but not with hydration (USG) or other biomarkers. Our PV estimates in this population were in line with those from previous studies.

Funding Sources: Bill & Melinda Gates Foundation (INV-016930)