Postpartum weight retention (PPWR) is a common problem among women after childbirth. The main objectives of this study are to understand the changes in body weight of breastfeeding mothers during long-term follow-up and preliminarily explore the relationship between maternal body weight and human milk composition, including macronutrients, leptin, and adiponectin.

The study included a longitudinal cohort (122 mothers), and a cross-sectional cohort (37 mothers). The human milk, maternal weight, and dietary surveys were collected in the longitudinal cohort at different follow-up time points (1−14 days postpartum, 2−4 months postpartum, 5−7 months postpartum, and 12−17 months postpartum). The maternal body weight was analyzed using the responses in the survey questionnaires. A milk analyzer based on the mid-infrared spectroscopy (MIRS) was used to determine milk composition, and nutrition analysis software evaluated dietary intakes. In the cross-sectional cohort, participating mothers were asked to provide blood and human milk samples and pertinent information related to maternal body composition. Maternal body composition was measured by bioelectrical impedance analysis (BIA), while ELISA analyzed leptin and adiponectin in milk and serum.

At 5−7 months postpartum, the PPWR of breastfeeding mothers was (2.46 ± 3.59) kg. At 12−17 months postpartum, the PPWR was (0.98 ± 4.06) kg. PPWR was found to be negatively correlated with milk fat content within 14 days postpartum and positively correlated at 2−4 months postpartum. In addition, the maternal weight and body muscle mass were positively correlated with leptin and adiponectin in milk. Plasma leptin was positively correlated with the mother’s body weight, body mass index (BMI), FAT percentage, and body fat mass, while plasma adiponectin did not correlate with any parameter. The results also indicate that the PPWR did not correlate with leptin and adiponectin in plasma or milk.

Breastfeeding mothers may retain considerable weight gain one year after delivery. Human milk composition may be related to changes in maternal body weight. Leptin and adiponectin in breast milk and leptin in plasma are associated with the maternal body composition. This study supports the notion that maternal nutritional status may affect offspring health through lactation, and future research should focus on exploring weight management of postpartum mothers.

This study explored the content and change trend of osteopontin (OPN) in breast milk and analyzed the relationship between OPN in breast milk and maternal body composition.

Breast-feeding mothers were recruited in Xinhua Hospital to collect breast milk and provide pertinent information. The content of OPN in breast milk was determined by enzyme-linked immunosorbent assay (ELISA). Determination of protein content in human milk was performed via the BCA method. The maternal body composition was determined by the bioelectrical impedance method. Serum glucocorticoid receptor α, adiponectin, insulin, and leptin were determined by ELISA. SPSS 25 was used for statistical analysis.

In the longitudinal cohort, 106 mothers provided 318 milk samples at different lactation periods. The results indicate that the OPN showed dynamic changes. OPN levels were (343.2 ± 163.5) mg/L during 114 days postpartum, (228.4 ± 121.5) mg/L during 24 months postpartum, and (204.8 ± 100.6) mg/L during 57 months postpartum. The content of OPN was very high in the first 114 days postpartum and then decreased. Compared with early postpartum milk, the OPN content of mature milk showed a significant relationship with maternal weight-related parameters. Additional body composition analysis was performed in 88 women at the mature milk phase. The results show that the OPN in milk is related to the mother's body composition, especially the content of skeletal muscle mass, but not to relevant humoral factors.

The levels of OPN in human milk of Chinese mothers showed dynamic changes with the extension of lactation time. The OPN in human milk was related to the mother's body composition but not related to related humoral factors.