Data from observational studies advocate vitamin supplementation for the prevention of miscarriage

Introduction

Vitamin supplementation is frequently recommended for women planning pregnancy. The benefits of supplementation are to lower the risk of congenital anomalies such as neural tube defects and reduce the risk of low birth weight, small for gestational age and preterm births.1,2

Data from observational studies advocate vitamin supplementation for the prevention of miscarriage, typically in the form of folate and B vitamins.

A Cochrane review on vitamin supplementation for preventing miscarriage found no evidence that taking vitamin A, vitamin C, multivitamins or folic acid prior to or in early pregnancy prevented pregnancy loss.3 However, the evidence showed that women receiving multivitamins plus iron and folic acid had a lower risk of stillbirth compared to taking iron and folate only (RR 0.92, 95% CI 0.85 to 0.99, 10 trials, 79,851 women; high‐quality evidence).3 Similar results with micronutrient supplementation in addition to iron +/- folic acid or with folate supplementation alone have also demonstrated no benefit in reducing pregnancy loss.1,2

Currently there is no known association between iron deficiency and RPL. However, iron deficiency anaemia should be corrected in the pre-conception period.

Bullet point guidance

  • Folic acid at a dose of 5 mg once daily should be considered in women with any of the following features: BMI³30 kg/m2; epilepsy; diabetes types 1 and 2; sulfasalazine therapy for IBD; neural tube defect in a previous pregnancy; hyperhomocysteinaemia; and sickle cell disease.5 However, folic acid has not been shown to prevent pregnancy loss in women with unexplained RPL.4
  • The following supplementation doses of vitamin D should be considered:

o 400 IU once daily for all pregnant women;

o 1000 IU once daily for women at high risk of vitamin D deficiency (i.e., increased skin pigmentation, reduced exposure to sunlight, BMI³30 kg/m2 and socially excluded women).6

  • There is no evidence that supplementation of micronutrients prior to or in early pregnancy prevents pregnancy loss. However, use of a multivitamin (e.g., Pregnacare) provides micronutrient supplementation to aid healthy pregnancy.
  • Iron deficiency anaemia should be corrected in the pre-conception period.

References

  1. De-Regil LM, et al. Effects and safety of periconceptional oral folate supplementation for preventing birth defects. The Cochrane Database of Systematic Reviews 2015:CD007950.
  2. Keats EC, et al. Multiple‐micronutrient supplementation for women during pregnancy. The Cochrane Database of Systematic Reviews 2019: CD004905.
  3. Balogun OO, et al. Vitamin supplementation for preventing miscarriage. The Cochrane Database of Systematic Reviews 2016: CD004073.
  4. Bender Atik R, et al. ESHRE guideline: recurrent pregnancy loss. Human Reproduction Open 2018(2): hoy004.
  5. Kennedy, D. and G. Koren, Identifying women who might benefit from higher doses of folic acid in pregnancy. Canadian family physician Medecin de famille canadien, 2012. 58(4): p. 394-397.
  6. RCOG, Vitamin D in Pregnancy – Scientific Impact Paper No. 43. 2014.