Table 1.

Overview of study populations, study period and exposure in the original trials and in the Vitabeginning follow-up study

Characteristics	Bangalore	Delhi	Dares Salaam
Original trials
Trial registration number	NCT00641862	NCT00717730	NCT00197548	NCT00421668
Intervention period	09.2010–08.2011	01.2010–03.2011	08.2001–02.2005	07.2007–05. 2011
Original sample size	366	1000	8468	2400
Exposure	Vitamin B12*	Vitamin B12 and/or folic acid†	Maternal multivitamins‡	Multivitamins and/or zinc§
Timing of exposure	Pregnancy (daily supplement from <14 weeks gestational age through 6-week postpartum)	Infancy/early childhood (daily supplement for 6 months from 6 to 30 months)	Pregnancy (daily supplement from 11-17 weeks until delivery)	Infancy (daily supplement from 6 weeks to 18 months)
Vitabeginning follow-ups
Expected sample size	230	800–900	366	446
Age range at follow-up	5–6.5 years	7–9 years	11–15 years	7–10 years
Start date of enrolment	01.2015	10.2016	07.2015	07.2015
Expected date for study completion	Estimated 07.2017	Estimated 11.2017	Estimated 11.2017	Estimated 11.2017

*From <14 weeks gestational age to 6 weeks postpartum vitamin B₁₂ 50 µg daily. In addition, all women were given iron and folic acid supplementation throughout pregnancy.

†From 6 to 30 months for 6 months; four groups: vitamin B₁₂, vitamin B₁₂ +folic acid, folic acid and placebo, doses >12 months: vitamin B₁₂ 1.8 µg and folic acid 150 µg (half doses for <12 months).

‡From 12 to 27 weeks gestational age until delivery: multivitamin B₁₂ 50 µg, vitamin B₁ 20 mg, vitamin B₂ 20 mg, vitamin B₆ 25 mg, niacin 100 mg, vitamin C 500 mg, vitamin E 30 mg, folic acid 0.8 mg.

§From 6 weeks to 18 months, four groups; multivitamin + zinc, vitamin Z and placebo. Multivitamin <6m: vitamin B₁₂ 1 mg, vitamin B₁ 0.5 mg, vitamin B₂ 0.6 mg, vitamin B 60.6mg, niacin 4 mg, folic acid 130 µg, vitamin C 60 mg, vitamin E 8 mg. Zinc 5 mg >6 months multivitamins and zinc doses were double.