As per the outcomes of a randomized controlled trial published in ‘The American Journal of Clinical Nutrition’, prenatal (before birth) supplementation of Vitamin B12 boosts short-term maternal milk quality, while postpartum (after birth) use enhances the long-term breast milk status. This unique study by Dongqing Wang et al. intended to evaluate the consequences of prenatal and postnatal use of Vitamin B12 on maternal milk in women at 6 weeks and 7 months after childbirth.

Pregnant women joined the study between 2001 and 2004. Starting from recruitment (12 to 27 weeks of conception) until 6 weeks after birth, these women were given either oral multiple micronutrient supplements every day or a placebo. A subgroup of participants, from 6 weeks to 18 months postpartum, were randomly allocated to receive a postnatal supplement or placebo, containing 50 μg/day of Vitamin B12 plus other vitamins. The levels of Vitamin B12 in the breast milk were examined for 412 participants at both 6 weeks and 7 months postpartum.

The occurrence of Vitamin B12 concentration in breast milk (less than 310 pmol/L) was 73.3% at 6 weeks and 68.4% at 7 months postpartum. Prenatal supplementation elevated maternal milk Vitamin B12 levels at 6 weeks, without any impact at 7 months. Meanwhile, postnatal supplementation resulted in an increase in levels at 7 months (Table 1):

Variations in maternal milk Vitamin B12 status at 7 months were identified based on effect modification between prenatal and postnatal supplementation. The impacts of prenatal and postnatal supplements were notably heightened among women in the control group during the alternate period.

The prenatal supplement demonstrated stronger efficacy when paired with postnatal control, while the postnatal supplement exhibited increased effectiveness when combined with prenatal control. Hence, prenatal vitamin B-12 use benefits short-term human milk status, while postnatal use provides advantages for long-term human milk quality.