Get outside if you're planning to get pregnat!

A recent study in the Journal of Clinical Endocrinology and Metabolism showed a link between low serum levels of Vit.D early in pregnancy and an increase in the risk of having toxemia later in the pregnancy.

"Low vitamin D early in pregnancy was associated with a five-fold increase in the odds of preeclampsia," said Dr. Bodnar, who also is an assistant investigator at the university-affiliated Magee-Womens Research Institute (MWRI). "Data showed this increase risk persisted even after adjusting for other known risk factors such as race, ethnicity and pre-pregnancy body weight. Also troubling was the fact that many of the women reported taking prenatal vitamins, which typically contain 200 to 400 International Units of vitamin D," she said.

It's interesting to note that these women were taking prenatal vitamins with vitamin D in them, however the study doesn't mention how much time these women spent outside. From wikipedia

Vitamin D2 is derived from fungal and plant sources, and is not produced by the human body. Vitamin D3 is derived from animal sources and is made in the skin when 7-dehydrocholesterol reacts with UVB ultraviolet light at wavelengths between 270–290 nm. These wavelengths are present in sunlight at sea level when the sun is more than 45° above the horizon, or when the UV index is greater than 3. At this solar elevation, which occurs daily within the tropics, daily during the spring and summer seasons in temperate regions, and almost never within the arctic circles, adequate amounts of vitamin D3 can be made in the skin only after ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen. With longer exposure to UVB rays, an equilibrium is achieved in the skin, and the vitamin simply degrades as fast as it is generated.

In most mammals, including humans, D3 is more effective than D2 at increasing the levels of vitamin D hormone in circulation; D3 is at least 3-fold, and likely closer to 10-fold, more potent than D2. However, in some species, such as rats, vitamin D2 is more effective than D3. Both vitamin D2 and D3 are used for human nutritional supplementation, and pharmaceutical forms include calcitriol (1alpha, 25-dihydroxycholecalciferol), doxercalciferol and calcipotriene.

So sunshine without the use of sunscreen is very important to proper vitamin D balance. This goes into another rant of mine on the over usage of sunscreens, but that's for another day.
Vitamin D is fat soluble so you can ingest too much, so taking a supplement isn't really the answer. The answer is to get off your butt and go outside for a walk! Spend a little time in the sun!

I want to be sure to point out that newborns get their vitamin D stores directly from their mother, so a mom deficient in vitamin D is going to have a baby deficient in vitamin D. Vitamin D is very important to bone health. Vitamin D deficiency is linked to Rickets, Osteomalacia, and Osteoporosis.