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. 2017 Feb 1;16(1):5.
doi: 10.1186/s12940-017-0209-5.

The impact of high apparent temperature on spontaneous preterm delivery: a case-crossover study

Lyndsay A Avalos  1 , Hong Chen  2 , De-Kun Li  2 , Rupa Basu  3
Affiliations

The impact of high apparent temperature on spontaneous preterm delivery: a case-crossover study

Lyndsay A Avalos et al. Environ Health. .

Abstract

Background: Despite the prediction that temperatures are expected to increase in the future, little is known about the health effects of increasing temperatures on pregnant women. The objective of this study was to investigate the impact of apparent temperature on spontaneous preterm delivery (PTD).

Methods: A case-crossover study of 14,466 singleton spontaneous preterm deliveries occurring between January 1, 1995 and December 31, 2009 among Kaiser Permanente Northern California (KPNC) members was conducted. Preterm deliveries were identified through KPNC's Electronic Health Records (EHR) data. Data on gestational age at delivery, infant sex, and maternal address were also extracted from KPNC's EHR and linked to meteorologic and air pollution monitoring data based on residential zip code.

Results: An 11.6% (95% CI: 4.1, 19.7) increase in spontaneous PTD was associated with a 10 °F (5.6 °C) increase in weekly average (lag06) apparent temperature, during the warm season. During the cold season, increases in apparent temperature did not significantly impact the overall effect of spontaneous PTD (6.2%, (95% CI: -3.0, 16.2) per 10 °F (5.6 °C) increase in weekly average (lag06) apparent temperature). Significant differences in the relationship between apparent temperature and spontaneous PTD emerged for region, gestational age and infant sex, during the cold season. No significant differences emerged for air pollutants.

Conclusions: Our findings provide evidence for an increase in the odds of spontaneous PTD associated with increases in apparent temperature, especially during the warm season.

Keywords: California; Case-crossover; Epidemiology; Heat; Spontaneous preterm birth.

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Figures

Fig. 1
Fig. 1
Flowchart of Study Exclusion and Inclusion Criteria
Fig. 2
Fig. 2
a Estimated Percent Change Associated with a 10 °F(5.6 °C) Increase in Mean, Minimum, and Maximum Apparent Temperature and Spontaneous Preterm Delivery by Lag Time during the Warm Season. b Estimated Percent Change Associated with a 10 °F(5.6 °C) Increase in Mean, Minimum, and Maximum Apparent Temperature and Spontaneous Preterm Delivery by Lag Time during the Cold Season. O Minimum + Mean X Maximum
Fig. 3
Fig. 3
a Estimated Percent Change Associated with a 10 °F(5.6 °C) Increase in Weekly Average Apparent Temperature and Spontaneous Preterm Delivery during the Warm Season, Overall and by Region, Preterm Delivery Timing and Infant Sex. b Estimated Percent Change Associated with a 10 °F(5.6 °C) Increase in Weekly Average Apparent Temperature and Spontaneous Preterm Delivery during the Cold Season, Overall and by Region, Preterm Delivery Timing and Infant Sex
Fig. 4
Fig. 4
a Crude and Adjusted Models Estimating the Percent Change Associated with a 10 °F(5.6 °C) Increase in Weekly Average Apparent Temperature and Spontaneous Preterm Delivery for Five Air Pollutants (CO, NO2, SO2, O3, and PM2.5) during the Warm Season. b Crude and Adjusted Models Estimating the Percent Change Associated with a 10 °F(5.6 °C) Increase in Weekly Average Apparent Temperature and Spontaneous Preterm Delivery for Five Air Pollutants (CO, NO2, SO2, O3, and PM2.5) during the Cold season. O Crude + Adjusted
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