Hyperthermia vs. Childhood Cancer

High temperatures actually increase the risk of acute lymphoblastic leukemia in children? Is this true or false?

With the progress of society and the development of medicine, people pay more and more attention to the safety of pregnant women and fetuses. Whether it is the diet, supplies, environment in daily life, or the examination, medicine and surgical operation for diagnosis and treatment of diseases, there are abundant medical researches to weigh the pros and cons, analyze the safety and give suggestions.

The first three months of pregnancy are particularly important because the first 12 weeks of pregnancy are a critical period for the differentiation and formation of the main structures and organs of the fetus. If this stage is affected by harmful factors such as certain drugs, certain infections, environmental toxins, etc., serious malformations, miscarriages or birth defects are more likely to occur.

Previous studies have shown that exposure to high temperatures in early pregnancy can lead to fetal malformations. However, a recent study by the Yale School of Public Health and published in The Lancet suggests that exposure to high temperatures in early pregnancy may not only harm the fetus during pregnancy, but may also increase the fetus's risk of developing childhood malignancies in the future [1].

1. The risk of teratogenicity caused by high temperature in early pregnancy

Systematic reviews and meta-analyses have found a wealth of evidence to support the impact of fever during pregnancy on fetal health: when the core body temperature of pregnant women rises by more than 2°C (fever ≥ 39°C), the risk of fetal neural tube defects, congenital heart disease, and cleft lip and palate will increase significantly, and timely use of antipyretic drugs can play a protective role and reduce the risk of fetal developmental abnormalities caused by fever [2]. In addition to high fever caused by disease.

In addition to high fever caused by disease, high environmental temperatures can also have an adverse effect on fetal development. An environmental science study based on 34 years of official Hungarian statistical data showed that the longer a woman is exposed to hot weather (average temperature > 25°C, which is the average temperature. Considering the low temperature at night, it means that the temperature will be higher during the day) in early pregnancy, the more likely she will have an early miscarriage that is not clinically monitored [3]. Several studies have found that bathing methods such as hot tubs and saunas may raise the core body temperature of pregnant women to dangerous levels, thereby increasing the risk of multiple birth defects and the incidence of miscarriage. The higher the temperature and the longer the exposure time, the more significant some risks are [4,5]. However, moderate to intense prenatal exercise does not cause high fever or increase the risk of congenital abnormalities [4].

Based on these studies, clinically, active cooling measures are often required for fever in early pregnancy, and the cause of the fever should be found and targeted treatment should be given. In the process of prenatal examination, whether there has been a high fever in early pregnancy is also an important reference for assessing pregnancy risks.

2. High temperatures increase the risk of acute lymphoblastic leukemia in children

Previous studies have focused on the effects of heat exposure during pregnancy on embryonic and fetal development, but this study from the Yale School of Public Health is the first to directly assess the association between heat exposure during pregnancy and childhood cancer risk.

The study included 6,258 children with ALL and 307,579 children without the disease and found a significant association between high ambient temperature in early pregnancy and risk of childhood ALL, with the strongest association observed in Latino and non-Latino white participants at gestational week 8. During this week, children exposed to an average ambient temperature of 30°C had nearly double the risk of ALL compared with an average ambient temperature of 10°C.

The researchers analyzed: Early pregnancy is a critical period for the development of the hematopoietic system, and lymphocyte production begins around the 8th week of pregnancy. Harmful interference during the critical period of tissue development may have far-reaching effects, which may be the reason why exposure to high temperature environment in the 8th week of pregnancy has the strongest association with childhood acute lymphoblastic leukemia. Childhood acute lymphoblastic leukemia often originates prenatally, and the association found in this study confirms this theory. However, the mechanism of this association is not yet clear. Researchers speculate that it may be related to epigenetic changes, inflammation or oxidative stress.

3. Our suggestions

Fever, as an obvious disease symptom, often receives sufficient attention, but the impact of high ambient temperature on pregnant women has not yet attracted sufficient attention from the public or even medical staff. With extreme high temperature weather becoming more and more frequent, the health risks of high temperature are becoming more and more worthy of vigilance. Considering the impact of high ambient temperature on early pregnancy and fetal development, women who are preparing for pregnancy and those who are already pregnant should pay special attention to the comfort of the environment, stay in a high temperature environment as little as possible, avoid overheating the water when bathing, and try to shorten the hot bath time to reduce the potential risks brought by high ambient temperature.

Many people are afraid to take medicine or seek medical treatment when they are sick or have a fever because they are worried that the medicine will affect the fetus. In fact, almost every regular medicine has safe medication recommendations for special groups such as pregnancy, lactation, and children. When clinicians prescribe medicines to these special groups, they need to weigh the pros and cons and try to choose medicines with low or no risks to pregnancy and breastfeeding. If high-risk medicines have to be used due to treatment needs, it is often necessary to explain in detail to the patient. Therefore, there is generally no need to worry about medical staff in regular hospitals using drugs that are harmful to the fetus without authorization. Compared with drugs with controllable risks and medical staff with reliable professional skills, diseases and symptoms such as infection and fever may be more likely to cause adverse effects or even serious consequences on pregnant women and fetuses. Therefore, if you experience fever or other discomfort symptoms during pregnancy, you must seek medical attention and standardized treatment in a timely manner.

In recent years, the problem of global warming has become increasingly serious, and scholars in various fields have been continuously studying and following up. From the perspective of medicine, the impact of ambient temperature on human health may be greater than we imagined. There may be more public health problems in the future. Of course, there must be corresponding strategies to deal with them.

References:

[1] Rogne T, Wang R, Wang P, et al. High ambient temperature in pregnancy and risk of acute childhood lymphoblastic leukaemia: an observational study. Lancet Planet Health. 2024;8(7):e506-e514. doi:10.1016/S2542-5196(24)00121-9.

[2] Dreier JW, Andersen AM, Berg-Beckhoff G. Systematic review and meta-analyses: fever in pregnancy and health impacts in the offspring. Pediatrics. 2014;133(3):e674-e688. doi:10.1542/peds.2013-3205

[3] Hajdu T, Hajdu G. Post-conception heat exposure increases clinically unobserved pregnancy losses. Sci Rep. 2021;11(1):1987. Published 2021 Jan 21. doi:10.1038/s41598-021-81496-x

[4] Graham JM Jr. Update on the gestational effects of maternal hyperthermia. Birth Defects Res. 2020;112(12):943-952. doi:10.1002/bdr2.1696

[5] Li DK, Janevic T, Odouli R, Liu L. Hot tub use during pregnancy and the risk of miscarriage. Am J Epidemiol. 2003;158(10):931-937. doi:10.1093/aje/kwg243

Author: Doctor Flying Knife Cutting Rain

Reviewer: Lan Yibing, deputy chief physician, Department of Obstetrics and Gynecology, Zhejiang University School of Medicine

The article is produced by Science Popularization China-Creation Cultivation Program. Please indicate the source when reprinting.