Vitamin D Deficiency in Preconception & Pregnancy

Vitamin D Deficiency and Pregnancy

Preconception, Pregnancy and Vitamin D

When it comes to pregnancy and supplements, most people have heard they should take a pre-natal and/or a folic acid/folate supplement. That should cover the basis…right?

Maybe not. There are a few other nutrients that don’t get quite the same attention as folic acid that have pretty big impacts for mama and baby. The big ones are iron and vitamin D – today, we’re going to focus on vitamin D deficiency.

Vitamin D deficiency, especially in pregnancy, is very common. A 2015 study of 2000 women found that only 8% (EIGHT PERCENT!) of them had sufficient vitamin D levels. As someone who regularly tests vitamin D levels in their practice, I can say this is pretty much in line with what I see clinically. The vast majority of tests I run shows some degree of deficiency. Not entirely surprising up here in Alberta, Canada.

What is The Significance of Vitamin D Deficiency in Pregnancy?

Preecmlampsia. The main thing that keeps coming up in the research is an increased risk of preeclampsia. In 2022, a meta-analysis found that women with vitamin D deficiencies were 40-50% more likely to develop preeclampsia. If you’re not familiar, pre-eclampsia is one of the most common complications of pregnancy (although still rare – it occurs in about 1-3% of pregnancies in Canada). It is a condition of high blood pressure in pregnancy and causes organ dysfunction. It can be dangerous for mom and baby if it isn’t addressed.
• Risk of preterm birth and small birth weight – The relationship between birth weight and vitamin D has been looked at as well. Having a significant vitamin D deficiency (less than 30 nmol/L) meant a higher chance of preterm birth and a 59% greater chance of having a smaller for gestational age baby.
• Placenta complications – A study in 2021 found that those who were vitamin D deficient have 5x the risk of placental complications.
• Quality of life during pregnancy – There is also some evidence that women who have adequate vitamin D during pregnancy also might be more prone to back pain, fatigue, and sleep issues.

Nutrition During Pregnancy - Avoid Vitamin D Deficiency

Test, Don’t Guess

I always recommend screening vitamin D levels in my patients who are thinking of conceiving or who are pregnant.

Yes, there is probably vitamin D in your prenatal. No, it is not enough to fix a deficiency. And no, it is not safe to take it in high doses if you don’t know if you are low or not.

We should test in order to ensure you’re taking an appropriate, effective, and safe dose for you and baby.

I’ll be honest, I wish it were easier for pregnant people in Canada to get access to a vitamin D test. Hopefully this evidence will eventually change our standards of care for pregnant people.

Sooner Rather Than Later

The suspected role that vitamin D (and many nutrients for that matter) has in pregnancy is helping develop a healthy placenta. Healthy placenta translates into adequate nutrition getting to baby – the placenta is the blood/oxygen/nutrient highway between parent and baby. When there is inflammation or major nutritional inadequacies, there is impaired blood vessel formation in the placenta making it harder for baby to get what it needs.

After 20 weeks gestation, giving vitamin D doesn’t seem to have the same positive impact on outcomes, likely because the placenta formation is mostly complete at this time. This is why I am such an advocate for preconception care! Contact me today to get started. 


Vitamin D is important for healthy placenta development. Research is converging on a theme that vitamin D deficiencies increase risk of preeclampsia, placental complications, risk of preterm birth and small for gestational age (SGA) babies. It also likely impacts quality of life for pregnant person. Testing is important to ensure dosing is adequate and safe. Finally, the impact of supplementation is less effective after 20 weeks, so this is something we ideally address prior to or early on in pregnancy.

Test for Vitamin D Deficiency Before and During Pregnancy


Davies-Tuck M, Yim C, Knight M, Hodges R, Doery JC, Wallace E. Vitamin D testing in pregnancy: Does one size fit all? Aust N Z J Obstet Gynaecol. 2015 Apr;55(2):149-55. doi: 10.1111/ajo.12278. Epub 2015 Apr 21. PMID: 25900732.

Hu K-L, Zhang C-X, Chen P, Zhang D, Hunt S. Vitamin D Levels in Early and Middle Pregnancy and Preeclampsia, a Systematic Review and Meta-Analysis. Nutrients. 2022; 14(5):999.

Tous M, Villalobos M, Iglesias L, Fernández-Barrés S, Arija V. Vitamin D status during pregnancy and offspring outcomes: a systematic review and meta-analysis of observational studies. Eur J Clin Nutr. 2020 Jan;74(1):36-53. doi: 10.1038/s41430-018-0373-x. Epub 2019 Jan 25. PMID: 30683894.

Raia-Barjat, T., Sarkis, C., Rancon, F. et al. Vitamin D deficiency during late pregnancy mediates placenta-associated complications. Sci Rep 11, 20708 (2021).

Woo J, Penckofer S, Fagan M, Giurgescu C. Associations between Pregnancy-Related Symptoms, Serum 25(OH)D, and Physical Quality of Life in Pregnant Women. Nutrients. 2022 Jan 22;14(3):482. doi: 10.3390/nu14030482. PMID: 35276839; PMCID: PMC8839227.

About Dr. Jayelle

Dr. Haavaldsen grew up in St. Albert but her heart called her to British Columbia after high school. After a decade spent in BC pursuing post-secondary education (and adventures!), she returned to Edmonton to start her naturopathic practice.