Vitamin D deficiency in pregnancy (SQ-86)
Pregnancy is a special time for a woman. It is also a time when your nutritional requirements undergo a sea change to meet the growing needs of a developing body and to maintain and protect your own well-being.
Nutritional deficiencies in pregnancy, especially of folate and iron, can have serious consequences for the mother, birth outcome and health of the new-born. In this blog post, we are going to discuss the role of vitamin D deficiency in pregnancy. This is an important discussion as majority of pregnant woman are found to be deficient in vitamin D despite taking the recommended dosage of prenatal vitamins.
The risk for deficiency is especially high for women who are vegetarians, those who get limited sun exposure and those with darker skin. So, what does this mean for the health of the mother and infant?
Vitamin D in Pregnancy
The health benefits of vitamin D are mostly related to its role in maintaining healthy bones and teeth. There is also increasing awareness of its role in regulating inflammation and immune response. Several studies have found a strong link between low vitamin D levels and an increased risk of cardiovascular disease, insulin resistance, type 2 diabetes, autoimmune disorders and certain types of cancers. Now, let’s see why vitamin D status should be an important consideration for a pregnant woman too.
Vitamin D levels of an unborn child depends on the levels of vitamin D in the mother. The foetal requirements for vitamin D increase in the third trimester as this is the most important time for bone formation. However, vitamin D also play a critical role in early pregnancy as it may also impact your chances of implantation and the risk of miscarriage.
Studies show low levels of maternal vitamin D can result in poor outcomes for both the mother and the baby. It can increase your risk of miscarriage, preeclampsia and gestational diabetes. Vitamin D deficiency in mothers may also lead to low birthweight, poor growth, weak bones and increased risk of wheezing disorders, asthma, autoimmune diseases and obesity in the new-born. It may even affect the health of your child later in life. And the mother continues to be the primary source of vitamin D for her new baby well after birth. Maternal vitamin D status is critical for infant bone formation, an important process in the baby’s growth and development.
1. Increased risk of miscarriages
Approximately 20% of pregnant women suffer from miscarriage. There are many risk factors involved such as smoking, genetics, increased age, heavy lifting and obesity. Identifying and addressing risk factors that can be prevented should help avoid this tragedy to some extent.
Vitamin D deficiency may increase a woman’s risk of miscarriage. Studies show that vitamin D levels in a pregnant woman rises in early weeks of pregnancy even when the need for calcium is not very high. The active form of vitamin D in this period increases up to three times the normal levels. This sharp spike would be toxic to a person who is not pregnant as this will cause the calcium levels to rise to dangerous levels. 
This suggests that vitamin D may have some role in early pregnancy other than calcium absorption. It appears that vitamin D may be needed to regulate immune responses so that the mother’s body doesn’t reject the foetus. Many studies have previously explored the potential role of vitamin D in early pregnancy, and how low levels may influence implantation and miscarriage.
A recent 2018 study found that women who were planning to conceive after miscarriage and with desirable levels of vitamin D ‘before conception’ were more likely to get pregnant and have a healthy birth, compared to women with inadequate vitamin D. The study was published in The Lancet Diabetes & Endocrinology. 
Interestingly, the study also reported that vitamin D status in the eighth week of pregnancy was not associated with loss of pregnancy. The findings were interpreted as “Sufficient preconception 25-hydroxyvitamin D (≥75 nmol/L) was associated with increased likelihood of pregnancy and livebirth. Increased vitamin D concentrations before conception, but not in early pregnancy, were associated with reduced pregnancy loss.”
What amounts to desirable or healthy levels of vitamin D in pregnancy may still be unclear. But it is an important insight in itself that for a woman trying to conceive, having healthy levels of vitamin D may be an important strategy to reduce the risk of miscarriage. In fact, studies have shown that women with higher levels of the sunshine vitamin have a higher success with assisted reproductive technologies like IVF. This was also reported by the researchers of this new study.
2. Increased risk of bacterial vaginosis during pregnancy
- Most likely to affect women between the ages of 15 and 44 years
- Caused by an excessive overgrowth of bacteria. This disrupts the natural balance of the bacteria normally present in the vagina.
- In some cases, there are no symptoms while some women may experience symptoms like abnormal vaginal discharge, foul smell or itching.
However, there is considerable evidence that vitamin D supplementation may help in getting rid of asymptomatic BV. The researchers of a 2015 study concluded that “among women in reproductive age groups with vitamin D deficiency, the administration of 2000 IU/day vitamin D was effective in eliminating asymptomatic BV. This treatment could be useful in preventing the symptoms and side effects of BV.”  The researchers recommended vitamin D supplementation to prevent or manage BV among women who are deficient.
Vitamin D increases the production of cathelicidin, anti-bacterial proteins, in the body. This results in improved immunity of the genital tract, a possible mechanism through which vitamin D may be useful in preventing BV and associated risks in pregnancy.
3. Increased risk of gestational diabetes mellitus
Gestational diabetes develops only during pregnancy, usually during the last half of the pregnancy. In this condition a pregnant woman has high blood sugar levels, but which were normal before pregnancy. GD occurs when your body can’t make or use insulin, a hormone released by the pancreas. Insulin helps cells to use the circulating glucose and convert it into energy.
During pregnancy, the placenta makes hormones that supports baby’s growth and development. But these hormones also counter the action of insulin in the mother’s body, which raises the levels of glucose in the blood. While your blood sugar levels are typically restored to normal soon after giving birth, gestational diabetes can cause health complications in both mother and the baby. It may increase the risk of:
- Preterm delivery
- Caesarean section
- Mother developing high blood pressure and preeclampsia
- A baby born with larger than average size (macrosomia) and possibly resulting in respiratory distress
- Developing type 2 diabetes later in life for both mother and child
A recent systematic review and metanalysis also found that women with gestational diabetes had significantly lower levels of vitamin D than women with normal glucose tolerance.  The review explained that the positive role of vitamin D could be due to several mechanisms. For example, you need vitamin D for normal production and secretion of insulin by the pancreas. Insulin regulates the levels of glucose circulating in the bloodstream. In addition, vitamin D is also known to lower inflammation and improve insulin resistance in patients with diabetes mellitus, among other things.
Besides gestational diabetes, a low vitamin D status spells bad news in other areas. For example, this 2018 study suggests that persons with low vitamin D levels may have a higher risk of developing diabetes. More specifically, people with D levels below 30 ng/ml were five times more likely to develop diabetes than people with levels more than 50 ng/ml, the study reported. 
In addition, studies show that Vitamin D supplements can help improve your D levels, which helps in improving insulin levels and insulin sensitivity in people with type 2 diabetes with vitamin D deficiency. These are the same mechanism through which vitamin D supplements may also help women with gestational diabetes.
There is enough evidence that suggests a link between vitamin D deficiency and an increased risk of GDM. At the same time, more randomized controlled trials are needed to establish that vitamin D supplements can prevent gestational diabetes. Screening pregnant women for vitamin D deficiency may be a useful step in this direction.
4. Increased risk of pre-eclampsia
Pre-eclampsia is a condition where a pregnant woman:
- Develops high blood pressure
- Has a high level of protein in their urine
- Develops water retention and swelling in the feet, legs, and hands.
- Eclampsia, high blood pressure that can cause seizures during pregnancy
- Liver dysfunction and low platelet count in mother
- Premature delivery
- Low birth weight in the baby
Studies show that women with preeclampsia have lower levels of vitamin D in comparison to women without this condition. Can Vitamin D help you prevent preeclampsia? This study show that vitamin D supplementation can protect against recurring preeclampsia. It concluded that “Vitamin D supplementation therapy in pregnancy could help in reducing the incidence of gestational hypertension/preeclampsia.” 
Another study suggested that using Vitamin D supplements in patients with a history of preeclampsia in previous pregnancies may lower the risk of both preeclampsia and eclampsia in the present pregnancy. 
Multiple factors such as endothelial dysfunction and inflammation, play a role in the development and progression of preeclampsia. Vitamin D plays an important role in some of these risk factors. For example, vitamin D:
- Improves the functions of blood vessels
- Lowers blood pressure
- Regulates immunity
- Lowers inflammation
Vitamin D deficiency can be the reason for many health problems for the developing un-born child and also the new-born. It can increase the risk of:
- Low birth weight and ‘small for gestational age’ infants
- Poor bone health
- Poor growth and development in early life
- Autism and autoimmune disorders
- Respiratory disorders, asthma and wheezing disorders
- Hollis et al. New insights into the vitamin D requirements during pregnancy. Bone Res. 2017
- Ganguly et al. Vitamin D, the placenta and early pregnancy: effects on trophoblast function. J Endocrinol. 2018
- Mumford, SL, et al. Association of preconception serum 25-hydroxyvitamin D concentrations with livebirth and pregnancy loss: a prospective cohort study. The Lancet Diabetes & Endocrinology. 2018
- Bodnar et al. Maternal vitamin D deficiency is associated with bacterial vaginosis in the first trimester of pregnancy. J Nutr. 2009
- Taheri et al. Treatment of vitamin D deficiency is an effective method in the elimination of asymptomatic bacterial vaginosis: A placebo-controlled randomized clinical trial. Indian J Med Res. 2015
- Lu et al. Association between vitamin D status and the risk of gestational diabetes mellitus: a meta-analysis. Arch Gynecol Obstet. 2016
- Zhang et al. Vitamin D Deficiency Increases the Risk of Gestational Diabetes Mellitus: A Meta-Analysis of Observational Studies. Nutrients. 2015
- Amraei et al. Effects of Vitamin D Deficiency on Incidence Risk of Gestational Diabetes Mellitus: A Systematic Review and Meta-analysis. Front. Endocrinol. 2018.
- Park et al. Plasma 25-hydroxyvitamin D concentration and risk of type 2 diabetes and pre-diabetes: 12-year cohort study. PloS One. 2018.
- Sasan et al. The Effects of Vitamin D Supplement on Prevention of Recurrence of Preeclampsia in Pregnant Women with a History of Preeclampsia. Obstet Gynecol Int. 2017
- Bakacak et al. Comparison of Vitamin D levels in cases with preeclampsia, eclampsia and healthy pregnant women. Int J Clin Exp Med. 2015