Table 1. Summarized ORs with 95% CIs for the associations of MTHFR polymorphisms with H and HIP.
| Polymorphism | Genetic model | n | Statistical model | OR (95% CI) | P z | I2 (%) | P h | P e | |
| C677T | |||||||||
| Allele contrast | H & HIP | 99 | Random | 1.23 (1.16–1.31) | <0.001 | 56.0 | <0.001 | 0.280 | |
| H | 34 | Random | 1.30 (1.18–1.43) | <0.001 | 64.1 | <0.001 | 0.816 | ||
| HIP | 65 | Random | 1.19 (1.10–1.29) | <0.001 | 48.7 | <0.001 | 0.149 | ||
| Homozygous | H& HIP | 99 | Random | 1.47 (1.30–1.66) | <0.001 | 41.5 | <0.001 | 0.362 | |
| codominant | H | 34 | Random | 1.63 (1.34–1.98) | <0.001 | 54.1 | <0.001 | 0.497 | |
| HIP | 65 | Random | 1.37(1.18–1.58) | <0.001 | 31.0 | 0.011 | 0.495 | ||
| Heterozygous | H & HIP | 99 | Random | 1.18 (1.10–1.27) | <0.001 | 38.4 | <0.001 | 0.059 | |
| codominant | H | 34 | Random | 1.25 (1.11–1.40) | <0.001 | 43.1 | 0.005 | 0.979 | |
| HIP | 65 | Random | 1.14 (1.03–1.26) | 0.009 | 34.3 | 0.004 | 0.052 | ||
| Dominant | H & HIP | 101 | Random | 1.26 (1.17–1.34) | <0.001 | 48.2 | <0.001 | 0.711 | |
| H | 35 | Random | 1.36 (1.20–1.53) | <0.001 | 55.0 | <0.001 | 0.918 | ||
| HIP | 66 | Random | 1.19 (1.08–1.32) | <0.001 | 41.0 | <0.001 | 0.651 | ||
| Recessive | H & HIP | 109 | Random | 1.37 (1.23–1.52) | <0.001 | 43.7 | <0.001 | 0.072 | |
| H | 35 | Random | 1.43 (1.21–1.68) | <0.001 | 45.6 | 0.002 | 0.123 | ||
| HIP | 74 | Random | 1.34 (1.16–1.53) | <0.001 | 43.5 | <0.001 | 0.118 | ||
| A1298C | |||||||||
| Allele contrast | H & HIP | 20 | Fixed | 1.01 (0.92–1.11) | 0.791 | 29.2 | 0.108 | 0.112 | |
| H | 7 | Random | 1.05 (0.79–1.39) | 0.733 | 67.6 | 0.005 | 0.614 | ||
| HIP | 13 | Fixed | 1.01 (0.90–1.14) | 0.824 | 0.0 | 0.760 | 0.315 | ||
| Homozygous | H & HIP | 20 | Fixed | 1.06 (0.85–1.32) | 0.630 | 0.0 | 0.696 | 0.348 | |
| codominant | H | 7 | Fixed | 1.08 (0.78–1.50) | 0.649 | 0.0 | 0.658 | 0.735 | |
| HIP | 13 | Fixed | 1.04 (0.77–1.40) | 0.816 | 0.0 | 0.506 | 0.716 | ||
| Heterozygous | H & HIP | 20 | Fixed | 0.99 (0.84–1.17) | 0.928 | 35.4 | 0.060 | 0.818 | |
| codominant | H | 7 | Random | 0.96 (0.65–1.44) | 0.854 | 71.0 | 0.002 | 0.708 | |
| HIP | 13 | Fixed | 1.01 (0.86–1.19) | 0.918 | 0.0 | 0.760 | 0.716 | ||
| Dominant | H & HIP | 21 | Fixed | 1.06 (0.90–1.26) | 0.474 | 45.3 | 0.013 | 0.643 | |
| H | 8 | Random | 1.10(0.75–1.61) | 0.637 | 77.2 | <0.001 | 0.941 | ||
| HIP | 13 | Fixed | 1.01 (0.87–1.18) | 0.906 | 0.0 | 0.092 | 0.219 | ||
| Recessive | H & HIP | 20 | Fixed | 1.10 (0.89–1.36) | 0.392 | 0.0 | 0.709 | 0.621 | |
| H | 7 | Fixed | 1.15 (0.84–1.57) | 0.393 | 0.0 | 0.780 | 0.866 | ||
| HIP | 13 | Fixed | 1.06 (0.79–1.41) | 0.712 | 0.0 | 0.453 | 0.528 |
Abbreviation: MTHFR, methylenetetrahydrofolate reductase; H, hypertension; HIP, hypertension in pregnancy; OR, odds ratio; CI, confidence interval; P z, P value for association test; P h, P value for heterogeneity test; P e, P value for publication bias test; n, the number of studies.