Table 1. Summary of characteristics of included papers.

Characteristics	n = 60	%
Research methods
Qualitative	39	65.0
Quantitative	18	30.0
Mixed-methods	3	5.0
Study region (n = 61) a
Africa	9	14.8
Europe	30	49.2
The Americas	18	29.5
Western Pacific	4	6.5
Country income level (n = 63) b
High-income	50	79.4
Middle-income	6	9.5
Low-income	7	11.1
Focal group
Pregnant women	51	85.0
Lactating women	2	3.3
Pregnant and lactating women	7	11.7
Intervention type
Therapeutic-related intervention	37	61.7
Vaccine-related intervention	11	18.3
Interventional trial: type unspecified	12	20.0
Trial area (n = 68) c
Pregnancy/childbirth complications	23	33.8
Fetal/newborn research	7	10.3
Infectious diseases	23	33.8
Noncommunicable diseases	2	2.9
Mental health	2	2.9
Trial areas unspecified	11	16.2
Stakeholder groups (n = 102) d
Pregnant women	25	24.5
Postpartum women	28	27.5
Lactating women	1	1.0
Women who had breastfed in previous 5 years	1	1.0
Reproductive-aged women	1	1.0
Partners/husbands	4	3.9
Other family members	1	1.0
Community leaders and members	3	2.9
Health workers	14	13.6
Research staff	9	8.8
Research investigators	7	6.9
Ethics committee members, administrators, and regulators	7	6.9
Funders	1	1.0

^a One study conducted in Malawi (Africa) and United States (The Americas) [85].

^b One study conducted in low- and high-income countries [85], and 1 study conducted in low- and middle-income countries [78].

^c Eight studies address 2 trial areas [40,41,45,46,48,60,85,94].

^d Twenty-nine papers reported more than 1 participant group [43–45,47,51,53–55,57,61,62,64–67,71,73,74,82,85–87,89–91,94–97].