Maternal vitamin A levels during second and third trimester and associations with offspring’s birth weight: a longitudinal cohort post-hoc study

Background Vitamin A is vital for maternal and fetal health during pregnancy, with both excess and deficiency linked to adverse outcomes. This study examined maternal vitamin A by serum retinol levels in the second and third trimesters and their association with birthweight in a high-income setting. Methods This study is a post-hoc analysis of a merged dataset from 723 women with low-risk pregnancies in Norway. Clinical data and blood samples were collected in the second (week 18–22) and third trimester (week 32–36). Serum retinol was measured by high-performance liquid chromatography and offspring’s birthweight was collected from medical records. Regression analyses were performed to examine associations between retinol levels and offspring’s birth weight. Results None of the women had vitamin A deficiency (serum retinol ≤ 0.7 μmol/L) in the second trimester compared to 1.9% in the third trimester. Vitamin A insufficiency (retinol > 0.7–≤ 1.0 μmol/L) was present in 8.6 and 43% of the women in the second and third trimesters, respectively. Overall, 17.3% of the offspring had a birthweight ≥ 4,000 g and were classified as having macrosomia. Mothers of macrosomic offsprings had lower serum retinol levels in the third trimester and lower average levels across both trimesters compared to mothers of offspring adequate for gestational age. A 0.2 μmol/L decrease in maternal serum retinol, measured in the second, third, as an average of both trimesters and as the delta change between trimesters, was associated with an increase in birth weight ranging from 31 to 68 grams. Conclusion Vitamin A insufficiency was prevalent during the third trimester of pregnancy in a high-income setting. Maternal retinol levels were inversely associated with the offsprings’ birth weight and suggest that low maternal vitamin A levels may be associated with an increased risk of obesity in offspring. Considering the limitation of this study’s post-hoc design, these findings should be interpreted cautiously. Trial registration http://clinicaltrials.gov , Identifier, NCT00476567.