Table 8.
Summary of the outcome of studies on birth weight in which exposure was used as categorical variable
| Reference | Study design | Exposure | Timing of exposure/assessment | Com‐pound | Unit | Exposure high | Exposure low | n expos. high | n expos. low | n total | Mean difference (g) (95% CI) | Adjusted |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Shahraki et al. (2016) | RCT | Supple‐mentation | From 4 to 16 gw onwards | Pyridoxine HCl | mg/day | 40 | Ondan‐setron | 100 | 88 | 188 | −57 (−187, 73) | No |
| Schuster et al. (1984) | RCT | Supple‐mentation | From 6 to 21 gw onwards | Pyridoxine HCl | mg/day | 7.5–20 | 0–5 | 112 | 84 | 196 | 47 (−85, 179) | No |
| Shrim et al. (2006) | PC | Supple‐mentation | During 1st trimester | Pyridoxine HCl | mg/day | 50–150 | NR | 96 | 96 | 192 | 221 (68, 374) | No |
| de Weerd et al. (2003) | PC | Whole blood | Drawn at 6 gw | PLP | nmol/L | NR | NR | NR | NR | 240 | NS | NR |
| Chang (1999)(a) | CS | Cord blood | Birth | PLP | nmol/L | ≥ 50 | < 40 | NR | NR | 209 | 400 (299, 502) | No |
CI: confidence interval; CS: cross‐sectional study; expos.: exposure; gw: gestational weeks; HCl: hydrochloride; NR: not reported; NS: not significant; PC: prospective cohort study; PLP: pyridoxal phosphate; RCT: randomised controlled trial.