Effects of weather factors and maternal characteristics on preterm birth: a six-year retrospective study

BACKGROUND: Preterm birth represents a leading cause of neonatal morbidity and fatality globally. Recent research has increasingly focused on the potential influence of meteorological and ecological variables on adverse pregnancy outcomes, particularly in the context of environmental change. Despite this attention, the evidence is still inconsistent, and there is a paucity of data from humid subtropical regions. The present study investigates the association between weather variables and preterm birth in a humid subtropical region of Türkiye. METHODS: A retrospective observational study was carried out using hospital birth records from January 2018 to December 2023 at a tertiary referral center in Rize, Türkiye. Preterm birth was defined as delivery before 37 completed weeks of gestation. Meteorological variables, including monthly mean air temperature, relative humidity, precipitation, wind speed, surface atmospheric pressure, and solar radiation, were obtained from the NASA POWER database and matched to birth records by month and year of delivery. Multivariable binary logistic regression analysis was used to identify factors associated with preterm birth. RESULTS: The study included 1,767 deliveries, of which 681 (38.5%) were preterm births. Preterm birth occurred more frequently among women aged 35 years or older, male infants, and nulliparities. Univariate analyses indicated that relative humidity was significantly higher in preterm births than in term births (p = 0.004), whereas other meteorological variables did not show significant differences. In multivariable analysis, maternal age ≥ 35 years was associated with a higher likelihood of preterm birth compared with age 25-34 years, and nulliparity was also associated with an increased likelihood of preterm birth. Among weather factors, higher relative humidity was associated with an increased likelihood of preterm birth, whereas higher surface atmospheric pressure, wind speed, and solar radiation were associated with a decreased likelihood. Temperature and precipitation were not significantly associated with preterm birth. The regression model was statistically significant (p < 0.001) and explained approximately 9% of the variance in preterm birth. CONCLUSIONS: Certain weather factors, particularly relative humidity, surface atmospheric pressure, and wind speed, may be associated with preterm birth in humid subtropical regions. These findings suggest that certain meteorological factors may be associated with preterm birth; however, these associations should be interpreted with caution and do not imply causal relationships.