Table 3.

Vitamin D deficiency among immigrant pregnant women in the Nordic countries, with strength of evidence

Exposure/Intervention	No. of participants (No. of studies)	Outcome variable (primary or secondary)	RR (95% CI)	Effect (95% CI)	No. of studies rated as A, B orC	Strength of evidence (convincing, probable, limited-suggestive, limited-no conclusion)	Comments
Vitamin D deficiency pregnant women	N=227 Immigrant women n=227 Ethnic Norwegians n=61 (4 studies)	Vitamin D deficiency Severe vitamin D deficiency Vitamin D level Secondary hyperparathyroidism PTH level	Subnormal level (Calcidiol < 30 nmol/L): 2.78 (1.31–5.88) Low level (Calcidiol <20 nmolL): 6.90 (1.96–24.23) (25(OH)D3<30 nmol/L): 15.00 (5.13–43.83)	Difference in subnormal level (Calcidiol < 30 nmol/L): 62% (42–82%) Low level (Calcidiol <20 nmolL): 51% (30–72%) (25(OH)D3<30 nmol/L): 77% (62–92%) Difference in rate of secondary hyperparathyroidism (PTH > 5.5 pmol/L): 43% (25–61%) Difference in vitamin D level: S–25(OH)D3 –36 nmol/L (median) Difference in PTH level: 1 pmol/L (median)	4 B	Convincing