Potential influence of temperature and precipitation on preterm birth rate in Puerto Rico

Abstract

The preterm birth (PTB) rate for singletons born in the tropical Caribbean island Puerto Rico increased from 11.3% in 1994, which was comparable to rates in the U.S., to as high as 18.3% in 2006 before decreasing to 15.5% in 2012. A few studies have reported that weather extremes are associated with higher risk of preterm birth, however, the effects of ambient temperature and precipitation has not been well examined in Puerto Rico. We compiled child birth data from the National Center for Health Statistics and weather data from the National Oceanic and Atmospheric Administration from 1994 to 2012. We explored the association between the weather factors and PTB rates with a distributed lag non-linear model (DLNM). We did not find direct association of lagged effect of temperature on birth outcome over monthly timescales. Both high intensity and frequency of precipitation and high frequency of storm and flood events are associated with increased risk of PTB rates. While the weather factors do not explain the marked increase and decrease in PTB rate, we emphasize the negative effects on PTB from weather extremes particularly precipitation in Puerto Rico.

Figure 1

Locations of three selected municipals, i.e. Mayagüez, San Juan, and Ponce in Puerto Rico; and the three corresponding weather stations.

Figure 2

Annual distributions of PTB rates of single born babies from 1994 to 2012 (plot a) and monthly PTB rates (plot b) in Puerto Rico.

Figure 3

Cumulative relative risk (RR) of PTB rate in respect to the mean values for average temperature (left panels) and the number of days in a month with temperature above 32 °C (DX90) subjected to time lags up to 1 months in Mayagüez, Ponce and San Juan. The horizontal broken line represents the reference line, i.e. RR = 1. The red broken and solid lines represent 0- and 1- month lags, respectively. The blue and dark-green lines along the shaded area represent 95% confidence interval values. The vertical broken lines represent mean values. The line and color notations are consistent for all the plots.

Figure 4

Cumulative RR of PTB rates in respect to the mean values for monthly rain intensities (mm) and frequencies (DP10, number of days with rain intensities above 254 mm in a month) subjected to time lags up to 1 months in municipals of Puerto Rico.

Figure 5

Cumulative RR of PTB rates in respect to the mean values for monthly frequencies of storms and flood subjected to time lags up to 1 months in municipals of Puerto Rico.