United States: Over the last few years, heat waves have become more intense and frequent in the United States, impacting our health negatively even before birth, according to expanded research.
How was the research conducted?
The study involved 53 million births from the fifty most populous metropolitan areas in the United States over twenty-five years and identified a 2 percent increased rate in preterm births and 1 percent of early term births, where the multiday period of high heat was applied.
The study findings were published in the medical journal JAMA Network Open.
The prior evidence from previously held research indicated that elevated temperatures in the outdoors were associated with preterm births, which are classified as deliveries that occur before the 37 weeks of pregnancy.
However, this study focused on the outcomes of heat waves on a much grander scale, and in analyzing the birth data, the researchers matched the results with the meteorological data and noted that there were four consecutive days of high heat, which occurred between the months of May and September exclusive, for each metro area particularized, as aol.com reported.
The earlier research also indicated that in contrast to early-term, preterm births were even higher among mothers who were 35 years or older after a heat wave.
An early-term birth is when a baby is born any time after 37 weeks of pregnancy but before 39 weeks of gestation.
The disproportionate effect of heat waves on health
Heat waves were again observed to have negative perceivable impacts on perinatal health, but the populations under study did not suffer from them equally.
The researchers pointed out that younger mothers from racial minorities having low education levels had a 4 percent rate of premature births after the heat waves were conducted, as aol.com reported.
Some of the factors that may have led to that statistic may include having the expecting mothers exposed to a better or lesser extent to air conditioning in residence and having more or lesser financial ability to pay for the higher cost of electric bills due to air conditioning.
The pregnant women in those vulnerable groups could also have jobs that make them work in adverse and extreme conditions as well as make them be outside more often when temperatures are high, noted the researchers.
Moreover, there are several biological causes that can result in early labor consequent to heat stress. Hormones controlling the induction of labor can be affected by heat stress and dehydration as these factors narrow blood flow to the uterus and placenta.
Heat stress can also exercise oxidation stress, which then releases heat-shocked proteins that may trigger a reaction that can cause the onset of labor.
It also indicated that exposure to heat at work may lead to the premature rupture of the membranes, thus initiating labor. However, the study also established that even if the mother was able to avoid standing for long periods, heat at the workplace may also induce rupture of membranes, which in turn triggers labor. Ectopic delivery causes serious morbidity and mortality among neonates and perinates and subsequently contributes to various chronic diseases.
To the same extent, heat-related deaths and the emergence of heat waves as a new norm are indicative of the effects of heat on the health of people, especially those who are most vulnerable to extreme weather conditions.
This research could not have been timed any better given that the US Southwest is currently enduring its first heat wave of the year; temperatures are scorching with the heat already rising to the dangerous levels of triple digits much earlier in the year than usual.