During pregnancy, if you have low levels of vitamin D your baby will also have low levels at birth. Some studies link vitamin D deficiency in pregnancy with an increased risk of pregnancy complications like pre-eclampsia and gestational diabetes. Pre-eclampsia is a potentially serious condition in pregnancy associated with developing high blood pressure, affecting both mother and baby. Pre-eclampsia is also associated with an increased risk for preterm birth and caesarean section. Along with the risk for pregnancy complications, low maternal vitamin D during pregnancy is associated with low infant birth weight and newborn failure to thrive.

Vitamin D for newborns

As vitamin D helps the absorption of calcium from the gut into the bones, newborns with vitamin D deficiency are at risk of developing rickets, a condition that causes deformity and weakness of the bones. As breastmilk contains low levels of vitamin D, newborns rely upon the maternal stores passed on from the mother during gestation.

Vitamin D Pregnancy Risk Factors

Pregnant women at risk of vitamin D deficiency include:

• Women living in cooler climates with less year-round sunshine; for example, the southern states of Australia and the U.K.
• Women with darker skin (dark skin contains more melanin than pale skin, which reduces vitamin D absorption from sunlight).
• Women with clothing preference that limits the amount of sunlight to the skin.

Where do we get vitamin D?

Sun exposure and vitamin D production are linked – but too much sun can be a bad thing, too!

90% of the body’s vitamin D is obtained through direct sunlight on the skin, with only 10% coming from dietary sources such as dairy, eggs and fish.

Factors affecting how much vitamin D can be absorbed from sunlight include the time of year, geographic location, altitude, the time of day, and skin type.

In summer, people with fair skin generally require 5 minutes per day of exposure to their arms, hands and face. During winter, sun exposure is required as often as 30 minutes three times a week. On the contrary, people with very dark skin may need a minimum of 20 minutes of sun exposure per day during summer months and over 1 hour per day in winter. People with dark skin living in cooler climates are more at risk of vitamin D deficiency.

Managing vitamin D deficiency

If you have any risk factors for vitamin D deficiency, your doctor should order vitamin D pregnancy screening either before conception or early in your pregnancy. If you have low vitamin D pregnancy levels, your doctor will recommend you start taking vitamin D supplements daily, and to check your levels again in 3 months time.

Vitamin D supplement pregnancy side effects

Vitamin D is safe to take during pregnancy, provided you follow the recommended dosage and have your levels frequently re-tested. This is because vitamin D is stored in the body, so if you keep taking vitamin D beyond what your body needs, there is a risk of toxicity.

Too much vitamin D can cause nausea and vomiting, loss of appetite, abdominal pain, muscle weakness and fatigue; however, it is unlikely for you to reach this level of toxicity if taking a low dose of 1000-2000 IU per day.

Will baby need a vitamin D supplement?

If your vitamin D levels remain low throughout pregnancy, your bub will most likely require vitamin D3 baby drops after birth. Vitamin D for babies should only be given on recommendation by a paediatrician, and it is important to follow the dosage advised by your doctor. Babies that are formula-fed generally do not require extra vitamin D, as there is usually sufficient vitamin D added to infant formula.

Bibliography

1. Australian Government Department of Health [Internet]. Canberra, ACT, Australia. Pregnancy Care Guidelines. 47 Vitamin D status. 2019 May 17 [cited 2021 April 28]. Available from https://www.health.gov.au/resources/pregnancy-care-guidelines/part-g-targeted-maternal-health-tests/vitamin-d-status.
2. Buyukuslu N et al. Nutr Res. 2014 Aug;34(8):688-93
3. The Royal Hospital for Women [Internet]. Sydney, NSW, Australia. MotherSafe (NSW Medications In Pregnancy & Breastfeeding Service). Vitamin D in Pregnancy and Breastfeeding. 2013 November [cited 2021 April 28]. Available from https://www.seslhd.health.nsw.gov.au/sites/default/files/migration/Mothersafe/documents/VitaminDMarch2017.pdf.
4. van der Pligt et al. Nutrients. 2018 May 18;10(5):640.