Impressive evidence is emerging regarding how adequate vitamin D intake can reduce the risk of babies being born prematurely and improve the health of full term babies, as well. Earlier, researchers at the University of Calgary in Canada found a link between substandard vitamin D intake during pregnancy and low birth weight.  Interestingly, more premature births occur during the late winter months when Vitamin D levels are the lowest.     


The investigators, Dr Bruce Hollis and Dr Carol Wagner of the Medical University of South Carolina, Charleston, met rigorous safety tests which were required by the Federal Drug Administration. The study was funded by the National Institutes of Health.


Furthermore, the authors observed these effects at relatively modest differences in vitamin D intake.


Dr. Hollis and Wagner’s laboratory and clinics, at the University of South Carolina Medical School,  conducted a study of vitamin D supplementation of up to 4000 IU of vitamin D3 per day during pregnancy over many years. The mothers were given ten times the normal dose of vitamin D during pregnancy experienced a 50 per cent reduction in premature births and had fewer low birth weight babies.


The women, who all lived around Charleston, South Carolina, began taking 4,000 IUs per day of vitamin D after their first clinic visit at about three months of pregnancy. (4,000 IUs or international units equal 100 micrograms). A control group took 400 IUs, equivalent to the normal recommended dose in the US and UK. The women had their blood and urine tested monthly to ensure calcium and vitamin D levels was within safe limits.


Over the 2½ years of the study thousands of tests were made and monitored by an external safety committee. No test showed any adverse effect of the large dose of vitamin D.  The average level of vitamin D in the women’s blood increased by about 50 per cent.


About 600 women took part in the trial which included similar numbers of African Americans, Hispanic Americans and whites. Premature babies born to women taking high doses of vitamin D were reduced by half at both 32 and 37 weeks, and there were also fewer babies who were born “small for dates” — that is smaller than would be expected considering the length of time spent in the womb.


The mothers also experience a significant reduction in infections (25 percent), especially the flu and colds, as well as fewer vaginal infections. The primary causes of complications during pregnancy were also lowered by 30 percent among the women who took the high-dose vitamin D.  They include, high blood pressure, gestational (pregnancy related) diabetes and pre-eclampsia, a condition that occurs shortly before labor and delivery that causes high blood pressure,  and fluid retention, which if unresolved can become fatal.


The babies receiving vitamin D after birth also experienced fewer colds, and a reduced incidence of asthma.


“I’m telling every pregnant mother I see to take 4,000 IUs and every nursing mother to take 6,400 IUs of vitamin D a day,” said Dr Hollis. “I think it is medical malpractice for obstetricians not to know what the vitamin D level of their patients is. This study will put them on notice.”


The Charleston team is also conducting another trial, supplementing breastfeeding mothers with 6,400 IUs per day. This high dose enables women to make breast milk which has sufficient vitamin D for the baby’s needs, 400 IUs per day.


The entire study will not be completed for another 21.5 years, but preliminary findings are extremely encouraging.


They report thus far, that some mothers attain a robust nutritional vitamin D status with no observable adverse side-effects.


The vitamin’s benefits have been observed previously in uncontrolled studies of pregnant women and babies, but this is the first time they have been found in a scientific trial which met the most stringent criteria for “evidence-based inquiry”. The findings may make it necessary for health departments to revise advice presently given to pregnant and breastfeeding women in the United States.