BACKGROUND: Optimal thyroid function is particularly crucial during infancy. This systematic review and meta-analysis aimed to investigate the relationship between the mode of delivery and neonatal thyrotropin levels at birth. METHODS: We conducted a systematic search of MEDLINE/PubMed, Web of Science, Embase, Scopus, and the Cochrane Library for studies published up to 2023. Hedges' g with 95% confidence intervals (CIs) was calculated to compare mean TSH levels based on the mode of delivery. Additionally, TSH levels were compared based on blood sampling methods, heel blood vs. cord blood, using the same meta-analytic approach. A random effects model was employed due to the presence of heterogeneity. This study is registered with PROSPERO under the number CRD42024533649. RESULTS: A total of 1,438 studies were identified, of which 18 met the criteria for the systematic review. The meta-analysis of ten studies revealed significantly higher pooled TSH levels in neonates born via vaginal delivery compared to those delivered by cesarean section (Hedges's g = 0.390
P = 0.002). In the heel blood subgroup, no significant difference in TSH levels was found between vaginal and cesarean deliveries (Hedges's g = 0.167
P = 0.111). However, in the cord blood subgroup, neonates delivered vaginally exhibited significantly higher TSH levels than those delivered by cesarean section (Hedges's g = 0.493
P = 0.002(. CONCLUSION: The study found that the method of delivery has a significant impact on neonatal TSH levels, especially in umbilical cord blood samples, highlighting the need to consider delivery mode in evaluating neonatal health.