Importance: Appropriate infant feeding practices have the potential for long-term health effects. However, research findings on improving early infant feeding practices are limited. The wide use of mobile phone short message service (SMS) provides new opportunities for health promotion and services.

Objective: To assess the effect of an SMS intervention on infant feeding practices.

Design and setting: Quasiexperimental design with follow-up measures scheduled at 4, 6, and 12 months at 4 community health centers in Shanghai, China. Two community health centers represented the intervention group, and 2 other community health centers represented the control group.

Participants: In total, 582 expectant mothers were recruited during the first trimester. Expectant mothers were eligible to participate if they owned a mobile phone, were first-time mothers, conceived a singleton fetus, were older than 20 years and less than 13 weeks' gestation, had completed at least a compulsory junior high school education, and had no illness that limited breastfeeding after childbirth.

Intervention: Mothers in the intervention group received weekly SMS messages about infant feeding from the third trimester to 12 months' post partum.

Main outcomes and measures: The primary outcome was the duration of exclusive breastfeeding (EBF). Survival analysis was used to compare the duration of EBF between the intervention group and the control group.

Results: Compared with the control group, the intervention group had a significantly longer median duration of EBF at 6 months (11.41 [95% CI, 10.25-12.57] vs 8.87 [95% CI, 7.84-9.89] weeks). The hazard ratio for stopping EBF in the intervention group was 0.80 (95% CI, 0.66-0.97). The intervention resulted in a significantly higher rate of EBF at 6 months (adjusted odds ratio, 2.67 [95% CI, 1.45-4.91]) and a significantly lower rate of the introduction of solid foods before 4 months (adjusted odds ratio, 0.27 [95% CI, 0.08-0.94]).

Conclusions and relevance: An SMS intervention may be effective in promoting EBF, delaying the introduction of solid foods, increasing awareness of the World Health Organization breastfeeding guidelines, and improving knowledge of appropriate infant feeding practices for new mothers.