Effects of breastfeeding during pregnancy on maternal and newborn health and breast milk composition: Meta-analysis.

Background: Breastfeeding is essential health behavior for the health of the mother and child. The duration of breastfeeding often affects the likelihood of overlapping between breastfeeding and subsequent pregnancies.

Aim: This meta-analysis evaluated the effects of breastfeeding during pregnancy on maternal and newborn health outcomes and the composition of breast milk based on previous studies.

Methods: The study protocol was developed, and the article was written following the PRISMA guidelines. The screening was conducted in September 2024, and the study was registered with PROSPERO. A comprehensive search was performed using PubMed, Google Scholar, the Cochrane Library, EBSCO, Embase, the National Thesis Center, and the TR Index. The methodological quality of the included studies was assessed using the JBI quality assessment tools. Data were pooled through meta-analysis, and a GRADE evidence profile was generated.

Findings: The meta-analysis revealed that breastfeeding during pregnancy did not significantly affect birth weight, the incidence of miscarriage, preterm labor, or pregnancy complications. However, it was associated with an increased incidence of low birth weight and intrauterine growth retardation. Regarding breast milk composition, breastfeeding during pregnancy did not change the total protein or lactose content but resulted in a reduction in fat content. Subgroup analyses indicated that the effects of breastfeeding during pregnancy on maternal and newborn health were influenced by the level of development of the country in which the studies were conducted.

Key conclusions: Breastfeeding during pregnancy may impact breast milk composition and maternal and neonatal health.