American researchers believe that this factor should be taken into consideration by the medical community.
The miscarriage corresponds to a spontaneous cessation of pregnancy before the 22nd week of amenorrhea, viability threshold of the fetus. It is considered early if it occurs before the 14th week of amenorrhea or late if it occurs between the 14th and 22nd week of amenorrhea.
Factors that can favor its occurrence are of course already known, such as obesity, tobacco use, consumption alcohol or drugs… But for researchers from the Boston University of Public Health, this risk may be greater during the summer months.
A particularly high risk at the end of August
Between 2013 and 2020, nearly 12,200 women constituted the cohort followed by the researchers. Half of them (6,104) reported becoming pregnant within a year of enrolling in this study.
However, 1 in 5 women of this half experienced a spontaneous termination of pregnancy. Scientists have noted that “This risk was highest at the end of August (…) This seasonal pattern was evident almost exclusively for early miscarriage, that is, occurring within 8 weeks of the date of the last menstrual period, and the associations were stronger among women living in the South and Midwest of the United States. United States”. In the regions mentioned, the temperatures are higher there.
How can this increased risk be explained?
Specifically, pregnant women in North America had a 44% higher risk of early miscarriage. the risk of miscarriage in any week of pregnancy was found to be 31% higher at the end of August compared to the end of February.
Amelia Wesselink, study leader and professor of epidemiology, explains what these results mean: “Now we need to dig deeper into this to understand what types of exposures are most prevalent in the summer, and which of those exposures might account for the increased risk of miscarriage.” If the environment and / or lifestyles specific to summer are mentioned to explain this increased risk, the researchers do not give more details.
And they recognize the limitations of their study, including the lack of information that would help determine whether these events “were caused by malformations of the uterus, an abnormality of the uterine cavity or by genetic abnormalities (chromosomal abnormalities of the couple , of the embryo…)”, tells us femina.fr website. And that’s not all, since daily urine samples were not taken to test for pregnancy, so some early miscarriages may not have been recorded. However, their conclusion “fills a gap in information on seasonal miscarriage trends”.
