Abstract / Summary
Abstract Background Routine clinical data rarely capture when women who begin breastfeeding first record formula as the sole milk source, or which early characteristics mark women at higher risk. We described its timing and examined first-week feeding category as an early marker. Methods We analyzed a nurse-led postpartum follow-up program at a tertiary hospital in Taiwan (2021–2024) with assessments at one week and one, two, four, and six months. Among 651 women (one eligible pregnancy per woman) providing any breast milk at one week, the outcome was the first assessment at which formula was the sole milk source, irrespective of complementary foods. Discrete-time survival models estimated conditional odds ratios (OR) for first-week feeding category (direct breastfeeding, expressed breast milk, or mixed feeding), obstetric factors, Edinburgh Postnatal Depression Scale (EPDS) scores, and mastitis. Results During follow-up, 318 first formula-only records occurred across 1,511 evaluable person-periods; life-table cumulative incidence was 64.7% (57.2% when censoring at the first missed visit; 161 of 651 women censored earlier), and the six-month probability of remaining free of a first formula-only record was 35.3% (95% CI 31.1–39.5). First formula-only records were concentrated in the first four postpartum months, with the monthly-equivalent point estimate numerically highest at one to two months (20.1%). Compared with mixed feeding, pooled adjusted odds were lower for direct breastfeeding (OR 0.14, 95% CI 0.08–0.26) and expressed breast milk (0.34, 0.20–0.59). There was evidence of heterogeneity in associations across follow-up intervals (penalized-likelihood interaction p = 0.035), so pooled estimates are common-effect summaries. Cesarean delivery was associated with higher odds (OR 1.49, 1.12–1.97). Conclusions Under the available-visit analysis, first formula-only records were concentrated in the first four postpartum months, with the monthly-equivalent point estimate numerically highest from one to two months. First-week feeding category was strongly associated with a first formula-only record, but the observational design and category composition preclude causal interpretation of feeding route. Feeding status recorded at the first-week visit may provide a simple clinical marker for considering preference-sensitive support from before one month through four months.