Vitamin D Deficiency
During Pregnancy and Breastfeeding
A majority of pregnant women are low in vitamin D. Compared to women with fair skin, women with dark skin are even more likely to be vitamin D deficient. According to a study (1) from University of Pittsburgh, USA, 54% of black, pregnant women and 47% of white, pregnant women living in the northern USA were low in vitamin D, despite taking prenatal vitamins. In addition, this study found 46.8% of black newborns and 56.4% of white newborns to be low in vitamin D.
Pregnant women who are low in vitamin D are not limited to the USA, but are a worldwide public health problem. A study from Belgium (2) revealed that 88% of the pregnant women in the area of Liege, Belgium were low in vitamin D.
In a study from Sanjay Gandhi Postgraduate Institute of Medical Sciences, India (3), researchers found 84% of the pregnant women living in sun-drenched India were deficient in vitamin D.
Why Are Pregnant Women Low In Vitamin D?
Most women are low in vitamin D before they become pregnant. The problem simply gets worse during pregnancy. Many pregnant women stay indoors for a variety of reasons. Most women feel nauseated during early pregnancy. Later in the pregnancy, there’s a lot of discomfort and fatigue. Staying indoors and resting is therefore quite common during pregnancy.
Don’t Rely On Prenatal Vitamins For Your Vitamin D Needs.
Many pregnant women take a prenatal vitamin assuming it meets all of their vitamin requirements. Think again! Prenatal vitamins contain only a small dose of vitamin D - 600 I.U.; Studies (1, 4) have documented that many pregnant women and their newborns have low levels of vitamin D despite taking prenatal vitamins. My own clinical experience testifies to it.
Can Vitamin D Deficiency In The Mother Cause Vitamin D Deficiency In The Newborn?
The answer is yes. The growing fetus derives vitamin D from his/her mother. Therefore, low vitamin D in the mother leads to low vitamin D levels in the fetus. Several studies have found newborns to be low in vitamin D if their mothers were low in vitamin D.
EFFECTS OF VITAMIN D DEFICIENCY
Scientific studies show that low vitamin D during pregnancy may jeopardize the health of the mother as well as the newborn baby.
Studies show the following effects of low vitamin D in pregnant women and their newborns.
Risks To Mother:
1. High Risk for Gestational Diabetes
In the second half of pregnancy, some pregnant women develop gestational diabetes. The known underlying mechanism for gestational diabetes is insulin resistance caused by a variety of factors including placental hormones. Now, we know that vitamin D deficiency worsens insulin resistance and therefore, it is intuitive to consider vitamin D deficiency as one of the factors that causes gestational diabetes. In a study (5) from Royal North Shore Hospital, Australia, researchers found that pregnant women who were low in vitamin D had an increase in fasting blood glucose, blood insulin level and insulin resistance.
2. High Risk for Preeclampsia in Pregnant Women
Preeclampsia is a serious, potentially life-threatening condition that some women develop during the second half of their pregnancy. When a pregnant woman develops preeclampsia, her blood pressure becomes elevated, her ankles swell up and there is excessive wasting of proteins in the urine. There is a real danger to the life of the mother as well as the baby.
In an excellent study (6) from University of Pittsburgh, USA, researchers found that pregnant women who had low vitamin D had a 5-fold increase in the risk of preeclampsia. Studies have also shown that proper vitamin D supplementation (about 1200 I.U. a day) during pregnancy can reduce the risk for hypertension and preeclampsia.
3. Increased Risk for Cesarean Section
An interesting study (7) from Boston University, USA, showed that pregnant women with a low level of vitamin D are at high risk for cesarean section. In this study, researchers found that pregnant women who were low in vitamin D were 4 times more likely to have a cesarean section compared to women with an adequate level of vitamin D.
Risks To Newborn:
1. Low Birth Weight
Vitamin D plays an important role in the growth of the fetus. Scientific studies have documented that babies born to mothers with low vitamin D level are likely to have low birth weight.
2. Rickets and Soft Skull Bones (Craniotabes) at Birth
Vitamin D plays a vital role in the development of fetal bones. Deficiency of vitamin D can cause a delay in the maturation of the bones and can result in rickets and craniotabes. Rickets refers to bone deformities in children due to vitamin D deficiency. Craniotabes refers to soft skull bones at birth.
Rickets typically causes deformity of the bones of the legs, chest wall and generalized weakness of muscles. A study (8) from All India Institute of Medical Sciences, India, evaluated 98 infants and their mothers for vitamin D status and rickets. Rickets was present in 30% of infants with markedly low vitamin D levels [25 (OH) vitamin D less than 10 ng/ml.] Intake of vitamin supplement, sunlight exposure and mother’s 25 (OH) vitamin D were predictors of infants’ 25 (OH) vitamin D levels.
Craniotabes is the medical term for the soft skull bones at birth. It’s diagnosed if the examiner’s fingers can bend skull bones, which then pop back after pressure is released. It’s also called “ping-pong ball skull.”
Craniotabes can affect up to 30% of otherwise normal newborns. It is presumed to spontaneously heal in most cases by 2-3 months. This has led to the notion (without any scientific background) that physicians need not pay much attention to this condition.
What is the cause of craniotabes? Japanese researchers investigated and found the answer: vitamin D deficiency! In an excellent study (9) from Kyoto University Hospital, Japan, researchers found that the incidence of craniotabes was inversely related to sun exposure during the last four months of pregnancy. Incidence was highest if delivery took place during spring, because the pregnant mother had less exposure to the sun during the preceding winter. The incidence of craniotabes was lowest if delivery took place in fall because the pregnant mothers had more sun exposure during the preceding summer.
They also checked vitamin D, parathyroid hormone and x-rays of the hand in infants with craniotabes at one month of age. The results were amazing. Vitamin D level turned out to be low in the vast majority (over 90%) of these infants. More than one third even had early rickets. Those who were solely breast fed without any formula (formula contains vitamin D) had even lower levels of vitamin D. Ten percent of these infants even had secondary hyperparathyroidism. To learn more about secondary hyperparathyroidism, please refer to Chapter 6: Vitamin D Deficiency and Body Aches, Pains and Chronic Fatigue Syndrome
3. Decreased Bone Mass in Childhood
Vitamin D is extremely important for the health of bones. Vitamin D starts playing this vital role before you are born, while you are still in the uterus. The effects of low vitamin D on the fetus not only make bones weak at birth, but also appears to continue to adversely affect bones for the rest of childhood and perhaps adult life as well.
In a study (10), researchers from University of Southampton, U.K. followed children born to women with low vitamin D and measured their bone mass at age 9. The researchers were amazed to find that children with low vitamin D level at birth had low bone mass at age 9 compared to those children who did not suffer from vitamin D deficiency at birth. It appears that vitamin D deficiency during fetal development has long term negative effects on the health of bones.
4. Asthma and Type 1 Diabetes During Childhood.
Vitamin D plays an important role in the development of the immune system of the fetus. Therefore, newborns low in vitamin D are at increased risk for autoimmune diseases such as Type 1 diabetes and asthma.
In one study (11) from Harvard Medical School, USA, researchers found that vitamin D intake of pregnant women had an inverse relationship with the development of asthma in their child. In this study, pregnant women taking a higher dose of vitamin D of about 800 I.U. a day significantly reduced the risk of developing asthma in their child compared to women taking a lower dose of about 400 I.U. a day.
In another study (12), researchers from Finland found infants who received a large daily dose of vitamin D (2000 I.U. per day) had an amazing 80% risk reduction for the development of Type 1 diabetes.
5. Maternal Vitamin D Deficiency can also cause other medical problems in infants. These include under-developed teeth, congestive heart failure, low blood calcium and tetany. Tetany refers to involuntary spasms of muscles.
In summary, maternal vitamin D deficiency leads to deficiency of vitamin D in the fetus. Vitamin D deficiency poses risks to the health of the mother as well as the newborn. Moreover, it appears that the imprints of vitamin D deficiency during fetal life persists throughout childhood and perhaps, even into adult life and contributes to a number of chronic illnesses such as asthma, Type 1 diabetes and weak bones.
Therefore, by simply ensuring a good level of vitamin D during pregnancy and infancy, you can give your offspring a healthy start in life.
Low Vitamin D In Breast-fed Infants
Women who breastfeed their infants need more calcium, because calcium is an important ingredient of milk. Therefore, they need more vitamin D, because vitamin D is vital in the absorption of calcium from the intestines.
Breast milk has very little vitamin D. Therefore, women who breastfeed their infant must take a good dose of vitamin D themselves and also give their baby at least a daily dose of 600 I.U. of vitamin D.
Most pediatricians know that human milk is very low in vitamin D. However, what many pediatricians may not know is that low vitamin D in human milk is a reflection of low vitamin D in the lactating mother. It was brilliantly pointed out in a study (13) from Medical University of South Carolina, USA. The researchers showed that the milk of lactating women who had an adequate level of vitamin D contained vitamin D equal to the amount contained in infant formula.
In a novel study (14) from The Aga Khan University Hospital, Pakistan, researchers assessed vitamin D levels in seventy-one nursing mothers and their breastfed infants. Thirty-four mothers (48%) and 37 infants (52%) had severely low vitamin D levels (less than 10 ng/mL). A significant correlation was found between serum 25 (OH) vitamin D levels of infants under three months of age and their mothers. Significantly higher levels of vitamin D were found in uneducated mothers, mothers of lower socio-economic class and in those living in mud houses. The researchers found a high prevalence of vitamin D deficiency in nursing mothers and their infants predominantly in the upper socioeconomic class. These mothers of high socioeconomic status in Pakistan tend to follow a western life-styl e, avoiding the sun at all costs, applying sunscreen when outdoors and sheltering their infants from sun-exposure as well.
“So, What Should I Do?”
Get your vitamin D level checked if you plan to get pregnant. Try to get your vitamin D at a good level even before pregnancy. Continue proper vitamin D supplementation during and after pregnancy. Have your vitamin D level checked at least every 2 months during and after your pregnancy. Please note that if you breastfeed your baby, you need even more vitamin D supplementation. For details, please refer to Chapter 26, Treatment of Vitamin D Deficiency.
References:
1. Bodnar LM, Simhan HN et al. High prevalence of vitamin D insufficiency in black and white pregnant women residing in the northern United States and their neonates. J Nutr . 2007;137:447-452.
2. Cavalier E, Delanaye P, et al. Vitamin D deficiency in recently pregnant women. Rev Med Liege . 2008;63(2):87-91.
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9. Yorifuji J, Yorifuji T, et al. Craniotabes in normal newborns: the earliest sign of subclinical vitamin D deficiency. J Clin Endocrinol Metab . 2008;93(5):1784-1788.
10. Javaid MK et al. Maternal vitamin D status during pregnancy and childhood bone mass at 9 years: a longitudinal study. Lancet. 2006;367(9504):36-43.
11. Camargo jr C, Rifas-Shiman S, et al. Maternal intake of vitamin D during pregnancy and risk of recurrent wheezing in children at 3 y of age. Am J Clin Nutr 2007;85:788-795.
12. Hypponen E, Laara E, Reunanen A, et al. Intake of vitamin D and risk of Type 1 diabetes: a birth-cohort study. Lancet 2001;358:1500-1503.
13. Taylor SN, Wagner CL, Hollis BW. Vitamin D supplementation during lactation to support infant and mother. J Am Coll Nutr . 2008;27(6):690-701.
14. Atiq M, Suria A, Nizami SQ, Ahmed I. Maternal vitamin-D deficiency in Pakistan. Acta Obstet Gynecol Scand . 1998 Nov;77(10):970-3.