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Seasonal ambient temperature and particulate matter as discriminators of hyperemesis gravidarum severity: a
Şahide Akbulut1, Erhan Okuyan2, Mülaim Sizer3
1Department of Nursing, Faculty of Health Sciences, Batman University, Batman, Türkiye.
Introduction:
Ambient air pollutants and temperature may influence the clinical severity of hyperemesis gravidarum (HG), but their relative contributions remain unclear. This study aimed to determine whether particulate matter (PM₁₀), sulfur dioxide (SO₂), and ambient temperature were independently associated with severe ketonuria in pregnant women with HG.
Methods:
This retrospective observational study included 211 pregnant women diagnosed with HG. Clinical severity was defined by ketonuria category (severe ≥2 + vs. non-severe <2+). Covariates (maternal age, gestational week, BMI, Healthy Eating Index [HEI], gravida, PM₁₀, SO₂, and ambient temperature) were selected a priori based on literature and univariate screening. Multivariable binary logistic regression was used; model discrimination was assessed via ROC analysis.
Results:
The autumn/winter group showed significantly higher maternal age, gravida, and PM₁₀ exposure, and lower ambient temperature than the spring/summer group (all p < 0.001). In multivariable analysis, only lower ambient temperature (OR = 0.890, 95% CI: 0.845-0.938, p < 0.001) and higher maternal age (OR = 1.143, 95% CI: 1.057-1.237, p < 0.001) were independently associated with severe ketonuria; PM₁₀, SO₂, HEI, gestational week, BMI, and gravida were not significant (all p > 0.05). The model correctly classified 81.5% of cases (Nagelkerke R 2 = 0.426). ROC analysis confirmed ambient temperature (AUC = 0.799) and PM₁₀ (AUC = 0.754) as significant discriminators for severe versus non-severe ketonuria, while SO₂ was not (AUC = 0.532).
Conclusion:
Ambient temperature showed the strongest discriminative performance for HG severity among the environmental parameters examined, while the association of PM₁₀ was attenuated after adjustment for temperature. Maternal age was also independently associated with HG severity. These findings should be interpreted as associations rather than causal effects. Further prospective, multi-site studies incorporating individual-level exposure assessments are warranted to confirm these associations and elucidate the underlying mechanisms.
