. Author manuscript; available in PMC: 2019 Mar 24.

Published in final edited form as: Crit Rev Food Sci Nutr. 2017 Jun 28;58(5):755–769. doi: 10.1080/10408398.2016.1220915

Table 1.

Observational studies of vitamin D status in pregnancy and maternal outcomes

Study design	Place of study	Sample size	Gestational age at Vit D assay	Vit D Assay method	Outcome analyzed	Statistics (95% CI)	Study authors	Quality of evidence (GRADE system)
Case control	India	74 cases and 100 controls	On enrollment	ELISA	Preeclampsia	p= 0.0001	Singla et al, 2015	Moderate

Case control	Iran	59 cases and 59 controls	Before the onset of labor	ELISA, HPLC	Preeclampsia	OR 24.04 (2.10–274.8)	Abedi et al, 2014	Low

Case control	Iran	41 cases and 50 controls	Onset of labor	ELISA	Preeclampsia	P=0.0001	Mohagegh et al, 2015	Moderate

Case control	USA	717 cases and 2986 controls	<26 weeks	LC-MS	Preeclampsia	Adjusted RR 0.65 (0.43–0.98)	Bodnar et al, 2014	Moderate

Case control	Iran	40 cases and 40 controls	Anytime	CLIA	Preeclampsia	P=0.002	Sadin et al, 2015	Moderate

Case control	USA	1126 cases and 2327 controls	<20 weeks	LC-MS	PTL	P<0.01	Bodnar et al, 2015	Moderate

Case control	USA	79 cases and 113 controls	At delivery	CLIA, RIA	PTL		Thota et al, 2014	Moderate
					(Caucasian)	P<0.01
					(African American)	P<0.04

Case control	USA	839 cases and 2629 controls	<26 weeks	LC-MS	PTL	-	Bodnar et al, 2015	Moderate

Case control	China	821	On admission	ELISA	PTL	P<0.001	Zhu et al, 2015	High

Case control	India	46 cases and 46 controls	At delivery	ECLIA	C-section	OR 2.31 (0.77–6.92)	Sebastian et al, 2015	Moderate

Nested case control	Sweden	39 cases and 120 controls	12 weeks	ELISA	Preeclampsia	p=0.3	Gidlof et al, 2015	High

Nested case control	Canada	169 cases and 1975 controls	<20 weeks	ELISA	Preeclampsia	OR 2.23 (1.29–3.83)	Achkar et al, 2015	Moderate

Nested case control	USA	400	15–21 weeks	LC-MS	Preeclampsia	OR 1.4 (0.7–3.0)	Wetta et al, 2014	Moderate
Nested case control	USA	400	15–21 weeks	LC-MS	Spontaneous preterm birth	OR 1.3 (0.6–3.0)	Wetta et al, 2014	Moderate

Nested case control	Australia	5109	10–14 weeks	CLIA	Adverse pregnancy outcomes (SGA, preterm births, preeclampsia, GDM, miscarriage and stillbirth)	OR 1.20 (0.69–2.07)	Schnueur et al, 2014	High

Nested case control	USA	135 cases and 517 controls	On enrollment (Avg 16 weeks)	LC-MS/MS	GDM	P<0.05	Arnold et al, 2015	Low

Cross sectional study	Poland	280	11–13 weeks	ECLIA	Preeclampsia	Not significant	Bomba Opon et al, 2014	Low

Cross sectional study	USA	1591	16.4–36.9 weeks (mean 27.9 weeks)	CLIA/RIA	Preeclampsia	Adjusted OR 1.14 (0.77–1.67)	Burris et al, 2014	Moderate
Cross sectional study	USA	1591	16.4–36.9 weeks (mean 27.9 weeks)	CLIA/RIA	Gestational hypertension	Adjusted OR 1.32 (1.01–1.72)	Burris et al, 2014	Moderate

Cross sectional study	Egypt	160	On enrollment	RIA	Glycemic control in GDM	P<0.05	Lithy et al, 2014	Low

Cross sectional study	UK	1467	26 weeks	LC-MS	GDM	NS	Whitelaw et al, 2014	Moderate

Cross sectional study	Turkey	687	24–28 weeks	ELISA	Postpartum depression at		Gur et al, 2015	Moderate
					1 week	P=0.003
					6 weeks	P=0.004
					6 months	P<0.001

Retrospective cross sectional study	US	133	-	LC-MS/MS	Recurrent pregnancy loss	-	Ota et al, 2014	Low

Prospective study	Canada	655	6–13 weeks	LC-MS/MS	GDM	OR 1.48, p=0.04	Lacroix et al, 2014	Moderate

Prospective study	Korea	523	12–14, 20–22, 32–34 weeks	ECLIA	GDM and pregnancy outcomes (Apgar, miscarriage, birth weight)	Adjusted OR 0.647.	Park et al, 2014	Moderate

Prospective cohort study	Netherlands	2074	12 weeks	ELISA	Pregnancy related hypertensive disorders	OR 1.88 (0.79–4.48)	Weert et al, 2016	Low

Prospective cohort study	Spain	2382	Avg 13.5 weeks	HPLC	GDM	RR=0.92 (0.55,1.55)	Rodriguez et al, 2015	High
					PTL	p>0.4
					C-section	RR=0.60 (0.37,0.97)
					FGR, SGA, HC, B wt, length	p>0.4

Prospective cohort study	Australia	796	18 weeks	ELISA, LC-MS	Postpartum depression	OR 2.19 (1.26–3.78)	Robinson et al, 2014	Moderate

Cohort study	Australia	1040	At delivery	LC-MS/MS	Postpartum depression at		Gould et al, 2015	Moderate
					6 weeks	Adjusted RR 0.92, p=0.11 (0.84–1.02)
					6 months	Adjusted RR=0.96, p=0.41 (0.88–1.05)

Cohort study	Singapore	940	26–28 weeks	ID-LC-MS	GDM	(0.01–0.14)	Loy et al, 2015	Moderate
Cohort study	Singapore	940	26–28 weeks	ID-LC-MS	C-section	OR 1.39 (0.95–2.05)	Loy et al, 2015	Moderate

Cohort study	China	213	24–48 hrs after delivery	LC-MS/MS	Postpartum depression	P<0.0001, OR 7.17 (3.81–12.94)	Fu et al, 2015	Moderate

Retrospective cohort study	USA	235	5–12 weeks	ELISA	Pre- eclampsia, PTL, GDM, spontaneous abortion	Adjusted OR 1.01 (0.961–1.057)	Flood-Nichols et al, 2015	Low

Cohort study	US	2798	<26 weeks	LC-MS/MS	C-section, prolonged labor and instrumental delivery		Gernand et al, 2015	Moderate

Retrospective cohort study	UK	995	11–13 weeks	LC-MS/MS	Mode of delivery	P=0.53	Savvidou et al, 2012	Moderate

Abbreviations used: Vit D (vitamin D), ELISA (Enzyme Linked Immune sorbent Assay), CLIA (Chemiluminescent Immunoassay), LC-MS/MS (Liquid Chromatography tandem Mass Spectrometry), HPLC (High performance liquid chromatography), RIA (Radio Immune sorbent Assay), GDM (gestational diabetes mellitus), PTL (Preterm labor), SGA (small for gestational age), B Wt (birth weight), HC (head circumference), C-section (Cesarean section), FGR (Fetal growth rate)