prenatal vitamins remains the recommended daily intake for pregnant women.

Ideally, a prenatal vitamin would also contain the recommended daily intake of iron for pregnancy–27 milligrams (mg). However, if the high dose of iron supplements upset your stomach or make you too constipated, it’s fine to skip the iron as part of your prenatal vitamin before you’re actually pregnant. If you have anemia (iron deficiency), your doctor may recommend a higher dose than the standard 27 mg/day.

If your prenatal contains Vitamin A, make sure it’s in the form of beta-carotene rather than retinol, and that the dose does not exceed 100% of the daily recommended intake. High doses of the ‘active’ form of Vitamin A (retinol) can produce birth defects, particularly in early pregnancy.

• You may find a variety of B vitamins (thiamin, niacin, riboflavin, Vitamin B6, Vitamin B12) and/or Vitamin C in your prenatal as well.

Lastly, don’t expect a prenatal viatmin to deliver much by way of calcium; high doses of calcium interfere with iron absorption and therefore usually do not exceed 150mg in a prenatal vitamin which contains iron.

A new study finds that women who develop a severe form of pregnancy-related high blood pressure tend to have lower blood levels of vitamin D than healthy pregnant women -- raising the possibility that the vitamin plays a role in the complication.

In the current study, researchers found that vitamin D levels were generally lower among 50 women with early severe preeclampsia compared with those of 100 healthy pregnant women. The average vitamin D level in the former group was 18 nanograms per milliliter (ng/mL), versus 32 ng/mL in the latter group.

There is debate over what constitutes an adequate level of vitamin D in the blood. The findings, reported in the American Journal of Obstetrics & Gynecology, do not prove that lower vitamin D levels contribute to early-onset severe preeclampsia.
A few past studies have found an association between vitamin D and preeclampsia in general. Now more work is needed to see whether pregnant women's vitamin D levels predict the odds of preeclampsia developing -- and whether raising those levels with vitamin D supplements lowers women's risk of the complication, according to Dr. Christopher J. Robinson, of the Medical University of South Carolina in Charleston.

Of the preeclampsia group, 54 percent were deemed to have vitamin D deficiency (less than 20 ng/mL), versus 27 percent of the healthy group. Only 24 percent of women with preeclampsia had vitamin D levels greater than 32 ng/mL, compared with 47 percent of their healthy counterparts.

It is biologically plausible, Robinson said, that the vitamin could affect preeclampsia risk. Right now, it's generally recommended that pregnant women get anywhere from 200 to 400 IU of vitamin D per day; prenatal vitamins contain 400 IU.
For now, though, Robinson said, the 400 IU in "prenatal vitamins remains the recommended daily intake for pregnant women".