Table 3.
Randomized controlled trials supplementing pregnant women with individual micronutrients included in meta-analyses
| No. of trials starting during each gestational period (weeks) |
|||||||||
|---|---|---|---|---|---|---|---|---|---|
| Micronutrient | No. trials |
Total no. of pregnancies [range between studies] |
Country income context |
Dose (times RDA)* |
Pre pregnancy |
1-10 | 11-20 | 21-30 | >31 |
| Vitamins | |||||||||
| Vitamin A‡ (McCauley 2015157) |
19 | 169,337 [27-102,952] |
Low to Middle |
1–3 | 2 | 1 | 9 | 5 | 2 |
|
| |||||||||
| Vitamin B6 (Salam 2015158) |
4 | 1623 [22-1532] |
Middle to High |
1–53 | – | – | 2 | 1 | 1 |
|
| |||||||||
| Folic acid (De-Regil 201092) |
5 | 8357 [218-5502] |
Low to High |
1–11 | 5 | – | – | – | – |
|
| |||||||||
| Folic acid (Lassi 2013103) |
31 | 13,396 [20-2928] |
Low to High |
0.3–42 | – | 1 | 16 | 13 | 1 |
|
| |||||||||
| Vitamin C§ (Rumbold 2015159) |
8 | 2007 [60-815] |
Low to High |
1–12 | – | 1 | 6 | 1 | |
|
| |||||||||
| Vitamin D∥ (De-Regil 2016105) |
9 | 1271 [40-260] |
Low to High |
1–8 | – | – | 1 | 8 | – |
|
| |||||||||
| Minerals | |||||||||
| Iodine¶ (Bougma 2013130 and Zhou 2013129) |
9 | 1521 [35-1047] |
Low to High |
436– 4364 |
2 | – | 6 | 1 | – |
|
| |||||||||
| Iron# (Peña-Rosas 2015102) |
44 | 22,802 [13-5828] |
Low to High |
1–37 | – | 2 | 27 | 12 | 2 |
|
| |||||||||
| Iron/IFA (Haider 2013101) |
48 | 17,793 [13-3929] |
Low to High |
0.3–33 | – | 3 | 30 | 12 | 2 |
|
| |||||||||
| Zinc (Ota 2015111) |
21 | 11,774 [56-2124] |
Low to High |
0.5–8 | 1 | – | 17 | 3 | – |
We did not identify a meta-analysis that met our criteria for vitamin B12 or selenium. We identified no individual studies for vitamin E, thiamin, riboflavin, niacin or copper. IFA, iron and folic acid.
RDA used for pregnant women aged 19–30 years as the referent group.
One study gave a bolus dose (600,000 IU).
Only includes trials comparing groups with vitamin C to groups without vitamin C (does not include trials of vitamin C and vitamin E tested together).
Only includes trials comparing groups with vitamin D to groups without vitamin D; four trials of vitamin D gave participants bolus doses (ranging from 60,000 to 600,000 IU).
Three trials of iodine gave bolus injections (96–1600 mg).
Only includes trials comparing groups with iron to groups without iron, does not include trials of iron and folic acid tested together.