A recent Spanish study conducted by Dr. Perez-Ferre under the supervision of Professor Alfonso Calle-Pascual of the Medicina Universidad Complutense in Madrid, Spain, studied the association between vitamin D levels in pregnant women and pregnancy complications.
Perez-Ferre N, Torrejon MJ, Fuentes M, Fernandez MD, Ramos A, Bordiu E, Del Valle L, Rubio MA, Bedia AR, Montañez C, Calle-Pascual AL. Association of low serum 25-Hydroxyvitamin D levels in pregnancy with glucose homeostasis and obstetric and newborn outcomes. Endocr Pract. 2012 May 1:1-18.
They studied 266 pregnant women between June and September. They found that pregnant women with 25(OH)D levels above 30 ng/ml had an 8% chance of preterm delivery, while those with a 25(OH)D of less than 10 ng/ml had a 39% risk, almost a five-fold greater risk.
The authors found that only 25 of the 266 women had 25(OH)D levels above 30 ng/ml, while 66% had levels below 20 ng/ml. Not only were the women with the highest levels (>30 ng/ml) less likely to have a preterm delivery, they were less likely to have gestational diabetes (12% versus 34%), cesarean section (8% versus 38%) and much less likely to be acidotic at birth (pH 7.1 versus 7.4).
Also, the women with the highest levels had babies that weighed, on the average, 3 kg, while women with the lowest 25(OH)D levels had heavier babies. Like past research, this fits my theory that babies from a vitamin D sufficient pregnancy will be full term (they were) but weigh less (they did) and have shorter delivery times (not measured). I think Paliolithic women had to quickly deliver small, developed term babies who nursed quietly. Failure to do so may have meant the clan would leave you and your baby behind, or worse.
The authors called for measurement of 25(OH)D levels both before and during pregnancy. They also called for both vitamin D supplements and increased outdoor activities for pregnant women. They recommended 2,000 IU/day, which I would dispute is still inadequate, though it is better than most recommendations.
Professor Bruce Hollis has shown that the recommendation of 2,000 IU/day is inadequate for breast-feeding. He has also shown that 4,000 IU/day is better than 2,000 IU/day during pregnancy. On days you do not get full body sun exposure, we recommend 6,000 IU/day throughout pregnancy, 5,000 for mom and 1,000 for baby, to maintain natural vitamin D levels, around 50 ng/ml, which is about where breast milk is magically transformed into a rich source of vitamin D for the infants.