Table 1 Summary characteristics of included systematic review

Number of SR

Five SRs (Oliveira et al. [21]; Caminha et al. [19]; Neves et al. [20]; McCauley et al. [24]; Thorne-Lyman and Fawzi [25])

Six SRs (Chakhtoura et al. [26]; Christesen et al. [22]; Reid et al. [27]; De-Regil et al. [17]; Roth et al. [9]; Das et al. [28])

Supplementation: six SRs (Trowman et al. [29]; Cumming [30]; Buppasiri et al. [31]; Onakpoya et al. [32]; Arthur et al. [18])

Fortification: one SR (Das et al. [28])

Population details

Postpartum women, breastfeeding or not, from the region where vitamin A deficiency (VAD) is a major concern, i.e. low-income settings in India, Bangladesh, Indonesia, Tanzania, Gambia, Zimbabwe, Kenya, Ghana, Peru, and Brazil (Oliveira et al. [21])

Pregnant and puerperal women (Neves et al. [20])

Lactating women (Caminha et al. [19])

Pregnant women (Thorne-Lyman and Fawzi [25]; McCauley et al. [24])

Pregnant women (Christesen et al. [22]; De-Regil et al. [17]; Roth et al. [9])

Adult women of age > 18 years (Reid et al. [27])

Pregnant women, children, and adolescents (Chakhtoura et al. [26])

Children, adolescents, pre-pregnant women, women of reproductive age group, and post-menopausal women (Das et al. [28])

Adult women of age > 18 years (Trowman et al. [29]; Cumming [30])

Pregnant women (Buppasiri et al. [31]).

Obese/ overweight participants (Onakpoya et al. [32])

Pregnant and puerperal women (Arthur et al. [18])

Pre-pregnant women, women of reproductive age group, and post-menopausal women (Das et al. [28]) included

Intervention

Supplementation of vitamin A alone or in combination with other micronutrients (Oliveira et al. [21]; McCauley et al. [24]; Neves et al. [20])

Supplementation of vitamin A/beta carotene (Thorne-Lyman and Fawzi [25]; Caminha et al. [19])

Supplementation of vitamin D (Chakhtoura et al. [26]; Christesen et al. [22]; Reid et al. [27]; De-Regil et al. [17]; Roth et al. [9])

Fortified food with vitamin D along with other micronutrients (Das et al. [28])

Calcium supplementation with or without dairy products or combined calcium supplementation (Trowman et al. [29]; Cumming [31]; Buppasiri et al. [31]; Onakpoya et al. [32]; Arthur et al. [18])

Alkaline phosphatase and serum parathyroid hormone as a fortificant (Das et al. [28])

Outcomes of our interest

The five included SRs provided information on the effect of vitamin A supplementation on serum retinol levels (Oliveira et al. [21]; Caminha et al. [19]) and hepatic reserves (Oliveira et al. [21]) of the women, vitamin A contents in breast milk (Oliveira et al. [21]; Caminha et al. [19]; Neves et al. [20]), proportion of women with low vitamin A contents (Oliveira et al. [21]), secretary immunoglobulin A levels in colostrum (Neves et al. [20]), subclinical vitamin A deficiency (Oliveira et al. [21]; McCauley et al. [24]), and maternal anemia and hemoglobin (Thorne-Lyman and Fawzi [25])

Vitamin D supplementation: 25(OH)D levels at term/delivery (De-Regil et al. [17]; Roth et al. [9]; Chakhtoura et al. [26]), vitamin D symptoms (Christesen et al. [22]), bone mineral density (Reid et al. [27]), serum calcium levels (Chakhtoura et al. [26]), weight gain (Christesen et al. [22]); side effects of vitamin D (De-Regil et al. [17]), and hypercalcemia, hypocalcemia, hypercalciuria (Roth et al. [9])

Vitamin D fortification: serum vitamin D levels, serum calcium levels (Das et al. [28])

Vitamin D and calcium fortification: serum vitamin D levels, CTx and P1NP (bone resorption marker) levels (Das et al. [28])

The SRs assessed effect of supplementation on body weight, weight gain, BMI, body fat, bone mass, and anemia

Methodological quality (the detail scoring is provided in Additional file 4)

High quality (McCauley et al. [24]; Oliveira et al. [26])

Moderate quality (Neves et al. [20]; Thorne-Lyman and Fawzi [25])

Low quality (Caminha et al. [19])

High quality (De-Regil et al. [17]; Roth et al. [9])

Moderate quality (Chakhtoura et al. [26]; Christesen et al. [22]; Das et al. [28]; Reid et al. [27])

High quality (Buppasiri et al. [31])

Moderate quality (Trowman et al. [29]; Onakpoya et al. [32]; Das et al. [28])

Low quality (Cumming [30]; Arthur et al. [18])