Can respondent driven sampling be used to recruit new mothers? A mixed methods study in metropolitan Washington DC.

Background: Respondent driven sampling (RDS) is employed to recruit populations that are hard-to-reach, "hidden," or without a sampling frame. For new mothers (those with infants <6 months) in countries without national health care systems or registries, there is no sampling frame, and random samples may only be attained through costly strategies, e.g., random-dial calling.

Objective: To assess the feasibility of RDS to recruit new mothers.

Methods: In the initial study, we recruited 30 new mothers ("seeds") from a single birth hospital; each was given 3 referral coupons to give to other mothers ("referrals"). When our sample did not self-perpetuate with referrals, additional seeds were recruited. Demographics of seeds and referrals were compared. A subset of mothers participated in focus groups and were asked about their experience with RDS. We also conducted a second survey of new mothers to further assess feasibility of RDS in this population.

Results: Of the 402 mothers recruited in the initial study, 305 were seeds and only 97 were referrals. Referrals were more likely to be White, highly educated, older, and privately insured (all p≤0.001). Focus group participants indicated that the time required to meet other mothers was an important barrier. In the second survey we recruited 201 mothers; only 53.7% knew ≥1 mother whom they could invite to the study.

Conclusions: New mothers are not easily recruited using RDS because they have a limited number of contacts who are also new mothers. Those recruited through RDS are more likely to be older, Caucasian and of high socioeconomic status, indicating it is not an effective way to recruit a representative sample of new mothers.