Research Design: The investigators will use a three-arm cluster randomized controlled trial (cRCT) to determine the effectiveness and scalability of a social network approach to increasing knowledge and uptake of family planning in low-parity, married adolescent and young women aged 15 to 24. This study will take place across 51 randomly selected villages in the Maradi region of Niger from the districts of Aguie, Gazaoua, and Tessauoua. Approximately 450 villages exist across these three districts, of which 302 meet our eligibility criteria. Eligibility criteria for selection of villages includes villages being 1) located in the Aguie, Gazaoua, or Tessauoua), 2) rural (i.e., not designated as a market town or city), 3) Hausa or Zarma-speaking, 4) total population size of the village consistent with a population of approximately 30 married adolescent girls, and 5) located within 5 km of a health clinic (i.e., centre de santé intégré). Once selected, villages will be randomized to one of three treatment arms (17 villages/arm). Depending on the arm, low parity, married adolescent and young women will receive either the standard Kulawa program (Arm 1), the Kulawa program adapted with a social network approach (Arm 2), or no FP programming (Arm 3, i.e., control). The Kulawa program adapted with a social network approach will be developed by Save the Children based on formative research and will include delivery to both female participants and one of their female alters (a nominated socially connected community member). Note that in villages selected for Arm 2, 50% of eligible participants will be randomly selected to receive the Kulawa intervention with the social network approach, to test effects of diffusion and accelerated impact. The other 50% of eligible participants in Arm 2 will receive the program, if successful, after 24 months (see below and Table 1 for details of participants).

Formative Research: The investigators will begin by collecting data for formative research and intervention development. This research will involve conducting qualitative social network interviews villages proximal to those in the treatment arm. Research aims will be to understand the best way to develop the social network intervention modification, including developing methods for identifying alters to include in the Kulawa social network intervention. Qualitative interviews will also help the investigators measure norm and behavior change among this population. Approximately 20 interviews will be conducted, 10 interviews with low parity, married adolescent and young women ages 15-24 years and 10 interviews with an influential individual that they name (female member of the community, minimum age 15 years). Each interview will take 45-60 minutes. Interviews will be audio recorded, translated, and transcribed.

Pilot: Survey assessments will include FP use and related behaviors, decision-making, personal attitudes, social norms, and social network influences. Surveys will be piloted in two villages comparable to those selected for the trial, among eligible female participants (approx. 30 per village), their nominated alters, and husbands. Based on findings, the study tools and social network intervention strategy will be refined.

Effectiveness Evaluation: The 3-arm RCT trial will take place across 51 villages (i.e., 17 villages per district) in the Maradi region of Niger randomly assigned to 1 of the 3 treatment arms. Within each village, households with eligible, married females (see Human subjects for eligibility criteria) will be enumerated by village elders. All eligible females in the villages (approx. 30/village) will be approached for recruitment (see Recruitment for details). The study will have three longitudinal waves of data collection: baseline (conducted immediately prior to the intervention), midline (conducted 12-months post the start of intervention implementation) and an endline (conducted 24-months post the start of intervention implementation). Survey interviews will be conducted with all eligible low parity, married adolescent and young women in each village (N=1530, 510 each arm, see human subjects for eligibility criteria) and take 45-60 minutes. Surveys will be conducted by a trained research assistant orally in Hausa or Zarma (at the participants choosing) who will record participant responses on a tablet computer. At each time point, participating low parity, married adolescent and young women (egos) will name a female influential to her FP decision-making (an alter) using the same approach described in the Preliminary studies. This individual (known as the first-degree alter) will also be interviewed at each time point in the same fashion as the original respondent (1530 per wave). These individuals will also nominate another influential individual (known as the second-degree alter). In treatment Arms 1 \& 2 only, the second-degree alters will also be interviewed in the same fashion (N=1020 per wave). Second-degree alters will not be interviewed in control villages. If individuals are named by multiple participants, they will not be re-interviewed. In treatment Arms 1 \& 2 only, husbands of originally recruited participants will also be surveyed (N=1020) via a verbal 45-60-minute survey interview.

Analysis \& Dissemination: Difference-in-differences models will be used to detect the differences between baseline and follow-up across different arms. Geographic analysis will also be conducted to test for the effect of geographic factors on behavior and norm adoption. Data will be disseminated after each wave of data collection to local, national, regional, and global stakeholders.