| Summary: | Vitamin A is vital to maternal–fetal health and pregnancy outcomes. However, little is known about pregnancy associated changes in maternal vitamin A homeostasis and concentrations of circulating retinol metabolites. The goal of this study was to characterize retinoid concentrations in healthy women (<i>n</i> = 23) during two stages of pregnancy (25–28 weeks gestation and 28–32 weeks gestation) as compared to ≥3 months postpartum. It was hypothesized that plasma retinol, retinol binding protein 4 (RBP4), transthyretin and albumin concentrations would decline during pregnancy and return to baseline by 3 months postpartum. At 25–28 weeks gestation, plasma retinol (−27%), 4-oxo-13-<i>cis</i>-retinoic acid (−34%), and albumin (−22%) concentrations were significantly lower, and <i>all-trans</i>-retinoic acid (+48%) concentrations were significantly higher compared to ≥3 months postpartum in healthy women. In addition, at 28–32 weeks gestation, plasma retinol (−41%), retinol binding protein 4 (RBP4; −17%), transthyretin (TTR; −21%), albumin (−26%), 13-<i>cis</i>-retinoic acid (−23%) and 4-oxo-13-<i>cis</i>-retinoic acid (−48%) concentrations were significantly lower, whereas plasma <i>all-trans</i>-retinoic acid concentrations (+30%) were significantly higher than ≥3 months postpartum. Collectively, the data demonstrates that in healthy pregnancies, retinol plasma concentrations are lower, but <i>all-trans</i>-retinoic acid concentrations are higher than postpartum.
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