Table 29. The effect of maternal vitamin D status in gestation on risk of gestational diabetes (GDM) – Observational studies.
| First Author and year |
Bias score |
Study details |
Study type |
Confounders/ adjustments |
Number of weeks gestation when 25(OH)D was measured | Mean (SD) or median (IQR) 25(OH)D concentration (nmol/l) in cases of GDM | Mean (SD) or median (IQR) 25(OH)D concentration (nmol/l) in unaffected controls | Odds ratio (95% CI) of GDM from univariate analysis | Odds ratio of GDM from multivariate analysis | Conclusion | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Maghbooli, 2008 133 | 3 (med) | Tehran, Iran Overall cohort size=741 women Cases of GDM=52 Controls=527 |
Cross- sectional |
Nil. Cases significantly older, higher parity and higher BMI. |
24-28 weeks** | 16.49 (10.44)** | 22.97 (18.25)** | Not given | Not given | 25(OH)D3 significantly lower in individuals with GDM p=0.009 |
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| Clifton-Bligh, 2008 92 | 6 (low) | New South Wales, Australia Cases of GDM= 81 women Normal pregnancies=183 women |
Prospective cohort |
Age, BMI, ethnicity, season | Mean (SD) 28.7 (3.3) weeks | 48.6 (24.9) | 55.3 (23.3) | Not given | OR if 25(OH)D <50 nmol/l= 1.92 (0.89,4.17) | Significant difference in mean 25(OH)D between cases and controls (p=0.04). However no significant association between GDM and 25(OH)D deficiency (25(OH)D <50 nmol/l) 25(OH)D significantly negatively associated with fasting glucose, fasting insulin and insulin resistance in unadjusted analysis. After adjustments however only significant relationship remaining was with fasting glucose (r= −0.11 (−0.26, −0.01) |
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| Zhang, 2008 135 | 8 (low) | Omega Study, Seattle and Washington, USA Overall cohort size=953 women Cases of GDM=57 women (70% white) Controls=114 women (84% white) |
Nested case-control |
Controls frequency matched to cases for the estimated season of conception OR1 = Maternal age, race/ethnicity, family history of type 2 DM OR2 = as above plus pre-pregnant BMI Physical activity measured but not included in the analysis as did alter the OR by >10% |
16 weeks | 24.2 (8.5) | 30.1 (9.7) | 25(OH)D conc | Unadjusted OR (95% CI) | 25(OH)D conc | OR1 (95% CI) | OR2 (95% CI) | 25(OH)D is early pregnancy is significantly associated with an elevated risk of GDM | ||
| 75+ | 1 (refernce) | 75+ | 1 (ref) | 1 (ref) | |||||||||||
| 50-74 | 1.86 (0.86,4.01) | 50-74 | 1.86 (0.84,4.09) | 1.56 (0.69,3.52) | |||||||||||
| <50 | 4.33 (1.78,10.5) | <50 | 3.74 (1.47,9.50) | 2.66 (1.01,7.02) | |||||||||||
| P for trend | 0.001 | P for trend | 0.006 | 0.05 | |||||||||||
| Per 12.5 nmol/l reduction | 1.44 (1.16,1.69) | Per 12.5 nmol/l reduction | 1.36 (1.11,1.69) | 1.29 (1.05,1.60) | |||||||||||
| Farrant, 2009 90 | 5 (low) | Mysore Parthenon Study, India Cases of GDM=34 women Normal pregnancies=525 women |
Prospective cohort |
Maternal age, fat mass, diabetes status | 30 weeks | 38.8 | 37.8 | Not given | Not given | No significant association between serum 25(OH)D at 30 weeks and GDM. (p=0.8 for difference in mean between GDM and normal) 25(OH)D positively related to fasting 32-33 split proinsulin concentration. Negative association between 30 minute glucose concentration following GTT and 25(OH)D in those with 25(OH)D <50 nmol/l |
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| Soheilykhah, 2010 134 | 3 (med) | Iran Cases of GDM=54 women Controls=111 women |
Case-control | Nil Controls matched for gestational age, maternal age, maternal BMI |
24-28 weeks | 24.05 (20.65)** | 32.25 (35.8)** | 25(OH)D3 conc | OR (95% CI) of GDM | No multivariate analysis performed | Significantly increased risk of GDM if 25(OH)D3 <37.5 nmol/l.<50 | ||||
| <50 | 2.02 (0.88,4.6) | ||||||||||||||
| <37.5 | 2.66 (1.26,5.6) | ||||||||||||||
| Makgoba, 2011 136 | 7 (low) | London, UK Overall cohort size=1200 women Cases of GDM=90 women Controls=158 women |
Nested case-control |
Unclear how cases and controls were matched Cases had higher BMI, prior history of Type 2 DM and a family history of Type 2 DM, higher blood pressure. No difference in parity, smoking, method of conception Adjusted for: BMI, gestation age at blood sampling, smoking, ethnicity, parity, maternal age, conception status, previous GDM, month of blood sampling |
11-13+6 weeks | 47.2 (26.7) | 47.6 (26.7 | Not given | Not given | No significant association between serum 25(OH)D in first trimester and GDM. P=0.863 in univariate analysis; 0.782 in multivariate analysis 25(OH)D negatively associated with fasting glucose (p=0.0009), 2 hour glucose following GTT (p=0.002) and HbA1c (0.002) at 28 weeks in univariate analysis. After adjustments however the only significant relationship remaining was with 2 hour glucose (p=0.048) |
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| Baker, 2012 137 | 7 (low) | North-Carolina, USA Overall cohort=4225 women Cases of GDM=60 women Controls=120 women |
Nested case-control |
Controls matched by race/ethnicity Adjusted for: Maternal age, insurance status, BMI, gestational age at serum collection, season of blood test |
11-14 weeks | Mean not given | Mean not given | 1.25 (0.39,4.05) if 25(OH)D <50 compared with those with 25(OH)D >75 | 0.78 (0.22,2.78) if 25(OH)D <50 compared with those with 25(OH)D >75 | No significant association between serum 25(OH)D in early pregnancy and GDM | |||||
| 25(OH)D conc | N (%) | 25 (OH)D conc | N (%) | ||||||||||||
| <50 | 5 (8.3) | <50 | 8 (6.7) | ||||||||||||
| 50-74.9 | 11 (18.3) | 50-74.9 | 24 (20) | ||||||||||||
| 75+ | 44 (73.3) | 75+ | 88 (73.3) | ||||||||||||
|
Fernandez-Alonso, 2012 115 |
3 (med) | Almeria, Spain Cohort=466 women Cases of GDM=36 |
Prospective cohort |
Nil | 11-14 weeks | Overall mean not given | Not given | Not given | Not given | No significant association between serum 25(OH)D in early pregnancy and GDM (p=0.84 for difference in mean between GDM and normal | |||||
| 25(OH)D conc | N | ||||||||||||||
| <50 | 109 | ||||||||||||||
| 50-75 | 191 | ||||||||||||||
| >75 | 166 | ||||||||||||||
**
Measured 25(OH)D3