Vitamin D in Pregnancy and Lactation

Background: Vitamin D is vital throughout pregnancy and lactation for both maternal and infant health. Health Canada recommends women take the AI of 5ug/day of vitamin D during pregnancy, however, it is unknown how much vitamin D is necessary to ensure both mother and baby reach a vitamin D serum concentration of 25OHD>75nmol/L.

Purpose & Hypothesis: This project aims to determine maternal and infant responses vitamin D supplementation in pregnancy and lactation. It is hypothesized that the current AI of 5 μg of vitamin D will be inadequate for women and their infants in Canada to achieve optimal 25OHD concentrations (> 75nmol/L). Methods: Healthy pregnant women between 18-42 years of age without history of pregnancy complications will be recruited for a double-blind, randomized, controlled trial where they will receive one of three different dosages of vitamin D (10, 25 and 50ug/day) as part of a standard prenatal vitamin. The study at 18 plus/minus 3 weeks gestation and will carry on throughout pregnancy and lactation. Mother and infant vitamin D levels in breast milk and blood will be measured at regular intervals. Skin colour will be measured via light reflectometry. Bone biomarkers such as plasma osteocalcin and urinary n-telopeptide will be assessed. Dietary vitamin D intake and sun exposure will be estimated using a food frequency and lifestyle questionnaire. Data will be analyzed using multiple regression analysis controlling for baseline values. Expected Results & Conclusions: It is expected that greater vitamin D intakes (25, 50ug/day) will be necessary to raise maternal and infant serum concentrations to 25OHD>75nmol/L to avoid infant supplementation. This data will aid policy makers, mothers and healthcare workers in recommended and appropriate vitamin D dosage throughout pregnancy and lactation.

10 ug/day Vitamin D as part of standard pre-natal vitamin supplement, taken from 18 weeks gestation to 6 months postpartum.

25 ug/day Vitamin D as part of standard pre-natal vitamin supplement, taken from 18 weeks gestation to 6 months postpartum.

50 ug/day Vitamin D as part of standard pre-natal vitamin supplement, taken from 18 weeks gestation to 6 months postpartum.

Inclusion Criteria: Women between 18-42 years of age within 18 plus/minus 3 weeks gestation planning to breastfeed their infant a singleton pregnancy Exclusion Criteria: Any co-morbid condition such pre-gestational diabetes, TB, cardiac or renal disease, HIV/AIDS, chronic hypertension, inflammatory bowel disease, autoimmune disease, liver disease, or epilepsy; conditions associated with vitamin D malabsorption: celiac disease, gastric bypass; History of previous adverse pregnancy outcome [preterm delivery <37; weeks GA, stillbirth, severe pre-eclampsia, eclampsia, HELLP syndrome (hemolytic anemia, elevated liver enzymes, and low platelet count)]; Women will also be ineligible if they are taking more than 10 µg day supplemental vitamin D or drugs known to interfere with vitamin D metabolism (i.e corticosteroids).

Stamm RA, March KM, Karakochuk CD, Gray AR, Brown RC, Green TJ, Houghton LA. Lactating Canadian Women Consuming 1000 microg Folic Acid Daily Have High Circulating Serum Folic Acid Above a Threshold Concentration of Serum Total Folate. J Nutr. 2018 Jul 1;148(7):1103-1108. doi: 10.1093/jn/nxy070. Erratum In: J Nutr. 2019 Apr 1;149(4):698.

March KM, Chen NN, Karakochuk CD, Shand AW, Innis SM, von Dadelszen P, Barr SI, Lyon MR, Whiting SJ, Weiler HA, Green TJ. Maternal vitamin D(3) supplementation at 50 mug/d protects against low serum 25-hydroxyvitamin D in infants at 8 wk of age: a randomized controlled trial of 3 doses of vitamin D beginning in gestation and continued in lactation. Am J Clin Nutr. 2015 Aug;102(2):402-10. doi: 10.3945/ajcn.114.106385. Epub 2015 Jul 8. Erratum In: Am J Clin Nutr. 2016 Nov;104(5):1491.