Is Vitamin D Important During Pregnancy?
If you are parents, you want the best for your child. It can be nerve wracking when your child doesn’t meet the expected developmental milestones. When I saw a recent study titled “Association of maternal vitamin D status in pregnancy and neurodevelopmental outcomes in children” ( AL Darling et al, British Journal of Nutrition, 117: 1682-1692, 2017), I knew you would want to hear about it.
But first a bit of background: Based on blood 25-hydroxy vitamin D levels (considered the most accurate marker of vitamin D status):
- 8-11% of pregnant women in the US are deficient in vitamin D (<30 nmol/L).
- ~25% of pregnant women have inadequate vitamin D status (30-49 nmol/L).
- ~65% of pregnant women have adequate vitamin D status (50-125 nmol/L).
- ~ 1% of pregnant women have high vitamin D levels (>125 nmol/L).
In short, that means around 1/3 of pregnant women in the US have inadequate or deficient levels of vitamin D. The affect of inadequate vitamin D during pregnancy is not just an academic question.
It is a concern because inadequate vitamin D levels during pregnancy has been associated with gestational diabetes (diabetes during pregnancy), low birthweight babies, and a condition called pre-eclampsia (pre-eclampsia is characterized by the development of high blood pressure during pregnancy and can lead to serious, even fatal, complications for mother and baby).
The Cochrane Collaboration (considered the gold standard for evidence-based medicine) has recently reviewed the literature and has reported) that vitamin D during pregnancy “probably reduces the risk of pre-eclampsia, gestational diabetes, and the risk of having a low birthweight baby compared to placebo or no intervention.”
In short, this means the evidence is pretty good that inadequate vitamin D increases the risk of significant complications during pregnancy and that supplementation with vitamin D reduces the risk of those complications.
However, what about the effect of inadequate vitamin D during pregnancy on the development of the newborn child? Here the evidence is less clear. This study was designed to answer that question.
How Was The Study Designed?
This study followed neurodevelopmental milestones of 7065 children born to mothers in the Avon region of southwest England between April 1, 1991 and December 31, 1992. Maternal 25-hydroxy vitamin D levels were measured during pregnancy. The distribution of 25-hydroxy vitamin D levels in this population was very similar to that observed for pregnant mothers in the United States.
The children were followed from 6 months to 9 years of age and the following neurodevelopmental milestones were measured:
- Gross-motor skills, fine-motor skills, social development, and communication skills were measured at 6, 18, 30, and 42 months.
- Behavioral development (socialization, hyperactivity, emotional development, and conduct) was measured at 7 years.
- IQ was measured at 8 years.
- Reading skill (words/minute, accuracy, and comprehension) was measured at 9 years.
What Is The Effect Of Vitamin D On Childhood Development?
The study compared children of women who had inadequate vitamin D status (<50 nmol/L) during pregnancy to children of women who had adequate vitamin D status (≥50 nmol/L) during pregnancy. Here is what the study found:
The children of mothers with inadequate vitamin D during pregnancy had:
- Delayed gross-motor skills at 18 and 30 months.
- Delayed fine-motor skills at 30 and 42 months.
- Delayed social development at 42 months.
However, when they looked at later years, there was no significant effect of maternal vitamin D status on:
- Behavioral development at 7 years.
- IQ at 8 years.
- Reading skills at 9 years.
This is encouraging because it suggests that the effect of inadequate vitamin D during pregnancy does not have a permanent effect on childhood development. By the time they are 7 or older their nutrition and intellectual stimulation during childhood appears to outweigh the effect of their mother’s nutrition on their development.
In interpreting this information, we need to keep in mind that this study was performed in England, not in a third world country. In particular:
- England, like the United States, has supplemental food programs for disadvantaged children.
- England has an excellent educational system. So, we can assume these children also received intellectual stimulation as soon as they reached school age.
Is Vitamin D Important During Pregnancy?
If we focus on a healthy pregnancy, there is good evidence that inadequate vitamin D during pregnancy increases the risk of serious complications and that supplementation with vitamin D can reduce these complications. We also know that vitamin D deficiency during pregnancy can affect bone development in the newborn.
Thus, adequate vitamin D is clearly needed for a healthy pregnancy.
However, if we just consider the effect of maternal vitamin D on childhood development, it would be tempting to downplay the importance of vitamin D during pregnancy. This study focused on vitamin D, but studies focusing on other nutritional deficiencies usually give similar results.
In most of these studies, the effects of inadequate nutrition during pregnancy on childhood developmental milestones appear to be transient. Developmental delays are seen during the first few years of life but disappear as the children get older.
This is incredibly good news. It means that mild nutritional deficiencies during pregnancy do not have to handicap a child for life. If the children are given adequate nutrition and intellectual stimulation as they grow, the poor start they received in life can be erased.
It is also a caution. We already know that poor nutrition during childhood can affect a child’s behavior and intellectual development. If that child also received poor nutrition in the womb, their chances of normal childhood development may be doubly impacted.
In short, if adequate vitamin D during pregnancy improves early developmental milestones in children, that can be viewed as an added benefit.
The only question is how much vitamin D is needed. Fortunately, the present study cast some light on that question.
The study asked whether blood levels of 25-hydroxy vitamin D ≥75 nmol/L were more beneficial than blood levels ≥50 nmol/L. The answer was a clear no. That means an adequate vitamin D status during pregnancy is sufficient to support normal developmental milestones in children.
The current recommendation (DV) of vitamin D3 for pregnant women is 15 mcg (600 IU). Thus, my recommendations are:
- If you are pregnant, be sure that your prenatal supplement provides at least 600 IU of vitamin D3.
- If you are a woman of childbearing age, be sure that your multivitamin provides at least 600 IU of vitamin D3.
- Slightly more is OK but avoid mega doses unless prescribed by a health professional who is monitoring your 25-hydroxy vitamin D status.
- Because we all utilize vitamin D with different efficiencies, I would recommend asking for a 25-hydroxy vitamin D test and working with your health professional to keep your levels in the adequate range.
The Bottom Line
A recent study looked at the effect of mild vitamin D deficiency during pregnancy on childhood developmental milestones. The study found that children born to vitamin D-deficient mothers had:
- Delayed gross-motor skills at 18 and 30 months.
- Delayed fine-motor skills at 30 and 42 months.
- Delayed social development at 42 months.
This is concerning. However, when they looked at later years, there was no significant effect of maternal vitamin D status on:
- Behavioral development at 7 years.
- IQ at 8 years.
- Reading skills at 9 years.
The is encouraging. The reasons for this are discussed in the article above.
If we summarize this and previous studies, the bottom line is:
- Adequate vitamin D is clearly needed for a healthy pregnancy.
- If adequate vitamin D during pregnancy improves early developmental milestones in children, that can be viewed as an added benefit.
For more details and my recommendations on how much vitamin D you need, read the article above.
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.