Reference Study name Country Duration Funding	Design	Subject characteristics at baseline	Intervention	Incident cases	Results
Marathe et al. (1986) NR India B6: Day 6–15 of gestation Study: 0–20 weeks of gestation NR	Animal (rat) study Parallel N = 48 G1: 12 (control) G2: 12 G3: 12 G4: 12	Sex (% female): 100 Wistar rats, weight range 200–220 g	Pyridoxine hydrochloride: G1: 0 mg/kg per day G2: 200 mg/kg per day G3: 400 mg/kg per day G4: 800 mg/kg per day Background nutrient intake: All fed Hindustan Lever feed and water ad libitum B6 intake: NR Compliance: 100%	Pup weight	Pup weight (g, mean ± SD) G1: 6.57 ± 0.16 G2: 6.37 ± 0.16 G3: 6.26 ± 0.15 G4: 6.21 ± 0.12 Difference NS
Schumacher et al. (1965) NR USA 2 weeks pre‐pregnancy + during pregnancy NR	CT, parallel (rats) Inclusion criteria: Long‐Evans rat strain N = 55 G1 (control): n = 40 G2 (+pyridoxine): n = 15	Sex (% female): 100 Age: NR Weight (g, mean): G1 (control): 300 G2 (+pyridoxine): 300	Pyridoxine Doses (g/100 g diet) G1: 0.25 G2: 6.25 Background nutrient intake: NR Compliance: NR	Birth weight	Birth weight (g/litter, mean) (average weight provided only) G1: 6.2 G2: 6.1 Difference NS
Alton‐Mackey and Walker (1973) NR Canada 14 days pre‐pregnancy + during pregnancy NR	CT, parallel (rats) N = 48	Sex (% female): 100 Wistar rats, virgin Weight (g): 200	Basal diet supplemented with 400% National Research Council (NRC) recommendations for pyridoxine for 2 weeks prior to mating (control) During pregnancy, rats divided into six dietary groups. Basal diet supplemented with pyridoxine, % of NRC: G1: 400 G2: 100 G3: 75 G4: 50 G5: 25 G6: 0 Group size: NR Compliance: NR	Birth weight	Birth weight (g/four litters, mean ± SEM) G1: 78.2 ± 3.8 G2: 74.3 ± 3.6 G3: 66.7 ± 3.1 G4: 60.9 ± 3.7 G5: 47.8 ± 3.6 G6: 44.8 ± 3.1 G4, G5, G6 lower than G1, G2, G3, p < 0.05
Alton‐Mackey and Walker (1978) NR Canada 14 days prepregnancy + pregnancy NR	CT, parallel (rats) N = 186	Sex (% female): 100 Wistar rats, virgin Weight (g): 200	Basal diet supplemented with 400% National Research Council (NRC) recommendations for pyridoxine for 2 weeks prior to mating (control) During pregnancy, basal diet supplemented with pyridoxine, % of NRC: G1 (n = 31): 400 G2 (n = 31): 100 G3 (n = 31): 75 G4 (n = 31): 50 G5 (n = 31): 25 G6 (n = 31): 0 Group size: NR Compliance: NR	Birth weight	Birth weight (g/litter, mean) (read from Figure 1) G1: 50 G2: 41 G3: 39 G4: 38 G5: 30 G6: 7 G5 and G6 (0–25%) very low birth weight Birth weight of G1, G2, G3, and G4 normal Tests + p‐values NR
Ritchie et al. (1960) NR USA ~ 2nd month of pregnancy – delivery Public	RCT, parallel (swine) Inclusion criteria: Basis for equal allotment to two treatments: Size, sex, breed, litter N (randomised/completed) = 44/42 G1 (randomised/completed): n = 22/21 G2 (randomised/completed): n = 22/21	Sex (% female): 100 G1: Control G2: Intervention Pregnant	Pyridoxine‐HCl G1: Total pyridoxine (pyridoxine + pyridoxal + pyridoxamine) G2: Pyridoxine‐HCl Doses (mg/pound of diet) G1: 0.45 G2: 5 Background nutrient intake: NR but controlled and similar in both groups	Birth weight	Birth weight (pounds/litter mean ± SEM) G1: 29.1 ± 2.0 G2: 28.7 ± 2.0 Difference NS
Khera (1975) NR Canada Gestation day 6–15 Public	RCT, parallel (rats) Female Wistar rats N = NR n = 89	Sex (% women): 100 Weight range (g): 175–200	Pyridoxine hydrochloride Doses (mg/kg day): G1: 0 G2: 20 G3: 40 G4: 60 G5: 80	Birth weight + anomalies Types of anomalies investigated: Wavy ribs; lumbar ribs; sternal defects; and runts. Less commonly: pericardial haemorrhage and subcutaneous oedema	Birth weight (g/animal, mean ± SD) G1: 4.8 ± 0.4 G2: 4.8 ± 0.3 G3: 4.8 ± 0.3 G4: 4.9 ± 0.3 G5: 4.8 ± 0.4 Anomalies (no/total examine, frequency) G1: 10/201 G2: 12/193 G3: 10/206 G4: 6/230 G5: 9/243
Dalto et al. (2016) NR Canada 30 days Private	RCT, parallel (gilts) Inclusion criteria: NR N (randomised/completed/analysed) = 84/77/32	Sex (% female): 100 Age (d [range]): 135–170 Body weight (kg ± SD): 91.4 ± 1.0	Pyridoxine hydrochloride Doses (mg/kg feed) G1: 2.4 G2: 12.4 Compliance: NR	Embryo weight at 30 days of gestation	Embryo weight at 30 d of gestation (g, mean) G1: 22.75 G2: 20.12 Tests and p‐values NR

Mean ± SD, unless specified otherwise.

CT: controlled trial; d: day; Gx: group; HCL: hydrochloride; NR: not reported; NS: not significant; RCT: randomised controlled trial; SEM: standard error of the mean; SD: standard deviation; USA: United States of America.