fever during pregnancy

Fever during the first trimester of pregnancy is thought to lead to severe congenital malformations in children. Sass and colleagues recently investigated the links between fever during pregnancy and congenital malformations in a Danish cohort.


Fever is typically the body’s response to fight off infection. It consists of an increase in body temperature, which can disrupt normal protein formation. This can lead to the disruption of cell membranes, cell death, and disruption or stroke in the placenta. For women experiencing fever during pregnancy, these disruptions can result in congenital malformations in their children.

Sass and colleagues used the Danish National Birth Cohort study to investigate the effects of fever during the first trimester of pregnancy on congenital malformations in children. A total of 77,344 women reported a pregnancy and information about fever during pregnancy in this cohort study. The researchers then investigated the relationship of reported fever and congenital malformation in the first three and a half years of a child’s life. The results were recently reported in BMC Pregnancy and Childbirth.

A total of 8,321 women reported a fever during the first trimester of their pregnancy. There were 2,876 infants who were later diagnosed with a congenital malformation during the first three and a half years. There was no link between reporting fever in the first trimester and infant malformation. However, among infants with a congenital malformation, fever during the first trimester of pregnancy was associated with a higher risk of malformations in the face and neck, including the eye and ear, and in the genitals, as well as a reduced risk of malformations in the nervous system, urinary tract, or respiratory system.

It’s possible that fever during pregnancy does not appear to be linked to significant malformations because it actually causes such severe malformations that fetuses are miscarried early on, or that women who received prenatal screening for malformations aborted these fetuses, so that they did not show up in the cohort study. The women who enrolled in the cohort study may also be a relatively healthier population than the general population. These results are contrary to most other work on the links between fever during pregnancy and congenital malformations, and future work must address the potential biases in the cohort study.

Written by C.I. Villamil

Reference: Sass et al. Fever in pregnancy and the risk of congenital malformations. BMC Pregnancy and Childbirth (2017) 17:413.

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