Abstract. The effect of a folic acid supplement on birth weight and placental weight in women delivering in the early summer in Denmark was investigated.

Thirty-six women with normal pregnancy and expected delivery in the first half of June were selected consecutively. They were paired two and two, and allotted to two groups, one of which was supplied daily with 5 mg folic acid, and the second with tablets without folic acid, from the 23rd week of pregnancy. A significant correlation was found between erythrocyte folic acid and birth weight. The infants in the folic acid group were 12.7 per cent heavier than those in the control group (p < 0.01). A similar difference was found with regard to placental weight and the number of placental cells.