Prevalence and Risk Factors of Hypernatremic Dehydration in Exclusively Breastfed Neonates: A Systematic Review and Meta-Analysis

Background/Objectives: Exclusive breastfeeding improves infant health and development, while suboptimal breastfeeding increases risks of hyperbilirubinemia and neonatal hypernatremic dehydration (NHD). This study aims to estimate the prevalence of NHD associated with exclusive breastfeeding and to identify maternal and neonatal risk factors through a systematic review and meta-analysis. Methods: This systematic review followed PRISMA 2020 guidelines. A comprehensive search was conducted in PubMed, Scopus, Web of Science, LILACS, and the Cochrane Central Register of Controlled Trials from February to March 2025 without language or publication year restrictions. Observational studies evaluating healthy term neonates exclusively breastfed and diagnosed with NHD within the first 28 days of life were included. Two independent meta-analyses were performed to estimate pooled prevalence and associated risk factors using random-effects models. Methodological quality was assessed using the Newcastle–Ottawa Scale (NOS) and the Joanna Briggs Institute (JBI) tool. Results: A total of 97 studies were identified, and 13 met the inclusion criteria. Ten studies were included in the prevalence meta-analysis and seven in the risk factor meta-analysis. The pooled prevalence of NHD was 1.4% (95% CI: 0.0–5.0%), with high heterogeneity (I2 = 99.6%). Delayed initiation of breastfeeding (OR 6.02; 95% CI: 2.85–12.73), excessive neonatal weight loss > 10% (OR 69.28; 95% CI: 0.00–1.87 × 1012), low urine output (OR 8.51; 95% CI: 2.86–25.29), and maternal primiparity (OR 3.66; 95% CI: 1.67–8.02) were identified as the main risk factors. Poor breastfeeding technique, inadequate latch, and lack of early postnatal follow-up were consistently associated with NHD. Conclusions: NHD is a clinically relevant condition among exclusively breastfed term newborns. Early breastfeeding assessment, monitoring of neonatal weight loss and hydration status, and strengthened maternal support are essential to prevent severe complications.