Vitamin D and pregnancy
The NHS advises that pregnant and breastfeeding women, like all adults, need at least 10mcg (400 IU) of vitamin D each day and should consider taking this amount, especially during winter months when sunlight is more scarce1. Despite this guidance, up to half of the pregnant women in the UK are affected by vitamin D deficiency2, which can be linked to pregnancy complications including pre-eclampsia, gestational diabetes, preterm birth and babies who are smaller at birth3.
Women who, as well as being pregnant, are also among other groups classed as being most at risk of suffering from vitamin D deficiency (including those with darker skin tones, those who have little exposure to sunlight for cultural or social reasons, or people with a BMI of more than 30), should consider taking vitamin D all year round4.
The impact of vitamin D on pregnancy
Maternal vitamin D plays a key role during pregnancy. It is important to things such as foetal bone development, and there is evidence that foetal lung development and neonatal conditions such as asthma may also be related to vitamin D levels5. Meanwhile, pre-eclampsia and neonatal hypocalcaemia are among the complications most associated with morbidity, and studies have shown a statistical association between low levels of vitamin D and glucose intolerance6.
The Royal College of Obstetricians and Gynaecologists (RCOG) recommends taking vitamin D during pregnancy7 and in its 2014 impact report Vitamin D in Pregnancy, shared the following findings on the relationship between levels of 25(OH)D and possible complications during and after pregnancy.
- Pre-eclampsia: there is some evidence to suggest a link between low vitamin D and pre-eclampsia, although there are conflicting studies on the issue. Three studies demonstrated that women who developed pre-eclampsia were found to have lower levels of vitamin D than those who did not8-10, while levels <50nmol/l were said to increase the risk of severe pre-eclampsia by five times11.
- Low birth weight: a positive correlation between maternal levels of vitamin D and birth weight has been shown12, with one Australian study finding that mean birth weight was 200g lower in the children of mothers who are vitamin D deficient13 and another from the Netherlands finding that women deficient in vitamin D are almost 2.5 times more likely to have a baby that is small for its gestational age14.
- Impaired glucose tolerance in pregnancy: gestational diabetes mellitus complicates up to 16% of pregnancies15 and, while there is conflicting data on the relationship between levels of 25(OH)D and glucose intolerance, meta analysis of more than 30 different studies has shown there to be a link between having vitamin D deficiency and being more at risk of developing gestational diabetes16.
Taking vitamin D during pregnancy
As well as the general advice that pregnant women, like the rest of the population, should consider increasing their vitamin D intake by taking at least 10mcg (400 IU) each day17, there has also been specific guidance relating to pregnant women deemed to be among the groups most at risk of vitamin D deficiency and those specifically requiring treatment for vitamin D deficiency.
High-risk patients: women who are members of groups that are more at risk of vitamin D deficiency, such as those with limited exposure to sunlight, darker skin tones, or those with conditions such as obesity, are advised to take at least 25mcg (1000 IU) per day18. Women at high risk of pre-eclampsia are advised to take at least 20mcg (800 IU)19 a day combined with calcium.20
Patients undergoing treatment for vitamin D deficiency: For the majority of women who are deficient in vitamin D, treatment over a six-week period with a loading dose of 500mcg (200,000 IU) per week, followed by standard dose as per the guidance for the general population, is considered to be appropriate.21
Neonatal vitamin D levels depend directly on the vitamin D status of the mother during pregnancy, making the above recommendations very important. Advice from the government is that babies should be breastfed exclusively for at least the first six months21. As a precaution, it is recommended that babies under the age of one who are being breastfed should take a precautionary dose of 8.5 to 10 micrograms to ensure they get enough vitamin D22.
Disclaimer: Use care when prescribing in pregnancy, as high doses of colecalciferol may affect the fetus. Please refer to the SmPC prior to prescribing in pregnancy and breastfeeding. Vitamin D and its metabolites are excreted in breast milk. Overdose in infants induced by nursing mothers has not been observed, however, when prescribing additional vitamin D to a breast-fed child you should consider the dose of any additional vitamin D given to the mother.
8. Kolusari A, Kurdoglu M, Yildizhan R, Adali E, Edirne T, Cebi A, et al. Catalase activity, serum trace element and heavy metal concentrations, and vitamin A, D and E levels in pre- eclampsia. J Int Med Res 2008;36:1335–41.
9. Baker AM, Haeri S, Camargo CA Jr, Espinola JA, Stuebe AM. A nested case-control study of midgestation vitamin D deficiency and risk of severe preeclampsia. J Clin Endocrinol Metab 2010;95:5105–9.
10. Bodnar LM, Catov JM, Simhan HN, Holick MF, Powers RW, Roberts JM. Maternal vitamin D deficiency increases the risk of preeclampsia. J Clin Endocrinol Metab 2007;92:3517–22.
11. Robinson CJ, Alanis MC, Wagner CL, Hollis BW, Johnson DD. Plasma 25-hydroxyvitamin D levels in early-onset severe preeclampsia. Am J Obstet Gynecol 2010;203:366.e1–6.
12. Robinson CJ, Wagner CL, Hollis BW, Baatz JE, Johnson DD. Maternal vitamin D and foetal growth in early-onset severe preeclampsia. Am J Obstet Gynecol 2011;204:556.e1–4.
13. Bowyer L, Catling-Paull C, Diamond T, Homer C, Davis G, Craig ME. Vitamin D, PTH and calcium levels in pregnant women and their neonates. Clin Endocrinol (Oxf) 2009;70:372–7
14. Leffelaar ER, Vrijkotte TG, van Eijsden M. Maternal early pregnancy vitamin D status in relation to foetal and neonatal growth: results of the multi-ethnic Amsterdam Born Children and their Development cohort. Br J Nutr 2010;104:108–17
15. Royal College of Obstetricians and Gynaecologists. Diagnosis and Treatment of Gestational Diabetes. Scientific Impact Paper No. 23. London: RCOG; 2011
16. Aghajafari F, Nagulesapillai T, Ronksley PE, Tough SC, O’Beirne M, Rabi DM. Association between maternal serum 25-hydroxyvitamin D level and pregnancy and neonatal outcomes: systematic review and meta-analysis of observational studies. BMJ 2013;346:f1169
18. Dawson-Hughes B, Heaney RP, Holick MF, Lips P, Meunier PJ, Vieth R. Estimates of optimal vitamin D status. Osteoporos Int 2005;16:713–6.
19. Haugen M, Brantsaeter AL, Trogstad L, Alexander J, Roth C, Magnus P, et al. Vitamin D supplementation and reduced risk of preeclampsia in nulliparous women. Epidemiology 2009;20:720–6.
20. Ito M, Koyama H, Ohshige A, Maeda T, Yoshimura T, Okamura H. Prevention of preeclampsia with calcium supplementation and vitamin D3 in an antenatal protocol. Int J Gynaecol Obstet 1994;47:115–20.
21. Saadi HF, Dawodu A, Afandi BO, Zayed R, Benedict S, Nagelkerke N. Efficacy of daily and monthly high-dose calciferol in vitamin D-deficient nulliparous and lactating women. Am J Clin Nutr 2007;85:1565–71.
Job Code: FUL-519a Date of Preparation: June 2020