Are pregnant women at higher risk from COVID-19? A Swedish study

A new study published by the Public Health Agency of Sweden in its Brief Report shows that compared to non-pregnant women, pregnant and postpartum women with COVID-19 have a higher risk of requiring intensive care.

It was towards the start of April 2020 that the Public Health Agency of Sweden (PHAS) observed a shift in the number of pregnant and postpartum women who were being admitted to the intensive care unit (ICU) in Sweden because of confirmed COVID-19. Since the available literature did not provide a clear-cut answer, the current study aims at assessing the risk presented by pregnancy in terms of increased susceptibility to, the severity of, and poorer outcomes as a result of COVID-19.

How was the study carried out?

The researchers first looked at the number of pregnant women with COVID-19 treated in ICUs in Sweden and compared this with the number of non-pregnant women with the infection who required ICU care. The data is taken from the Swedish Intensive Care Registry (SIR) and provides a list of all such cases.

In most Swedish ICUs, the presence of laboratory-confirmed COVID-19 or influenza is also documented using a special reporting module, which helps to pick out pregnant women as well as those who have given birth.

The investigators collected data on all women between 20 and 45 years old who had COVID-19 between March 19, 2020, and April 20, 2020. In ascertaining the risk of requiring ICU admission in pregnancy or postpartum, it was found to be difficult to separate the pregnancy-related or other causes for ICU care from the COVID-19-related causes. As a result, the whole group of COVID-19-positive women who were pregnant or had just given birth was included in the analysis.

Using population data from the Swedish population registry, they found that on December 31, 2019, there were over 1.6 million women in this age group. There were around 1.16 million births, according to the 2018 Swedish Birth Registry. Assuming that deliveries occurred at the same rate throughout the year, at about 320 per day, and the gestational age of 40 weeks, the researchers estimated that about 95,000 women were pregnant during the study period.

To account for the number of stillbirths and miscarriages, the researchers included another 50% in the first sensitivity analysis. In the second, they included only those women who required invasive mechanical ventilation since pregnant women might be more readily admitted to the ICU than others. The third analysis used both aspects.

As a control group, and to understand how many patients would need ICU care in an epidemic, the researchers looked at the total number of pregnant women in this age group who required intensive care with influenza, in the flu season of 2015-16, was collected. The total number of pregnant women in Sweden in the same period was also estimated.

What did the study show?

There were 53 women in the age group 20-45 with COVID-19 who required ICU admission in the study period. This includes 13 pregnant and newly postpartum women. The age ranged from 20-35 years, with pregnancy term between weeks 13 and 40.

Some women had gestational diabetes, and others had obesity. Seven of them delivered the baby, five by Cesarean section. Of these, two were for non-obstetric reasons, namely, COVID-19 symptoms.

There were seven pregnant women in all who needed mechanical ventilation compared to the 29 (out of 40) non-pregnant women. The median stay in the ICU was six days.

The incidence of COVID-19 cases requiring intensive care in Sweden was 14.4/100,000 for pregnant or postpartum women, and 2.5/100,000 for non-pregnant women in this age group. The sensitivity analyses showed the same trend, with an incidence of 7.4 and 1.8 per 100,000 for pregnant and non-pregnant women, respectively, when considering only those women who underwent invasive mechanical ventilation.

The analysis covering the risk of requiring ICU care in the flu season was about 4 and 1.8 per 100,000 pregnant and non-pregnant women, respectively. The relative risk of receiving intensive care was, therefore, higher for pregnant and postpartum women with COVID-19 than for non-pregnant women with COVID-19 in the same age group, in all analyses.

The scientists acknowledge that they could not find out why each woman was admitted to the ICU, whether pregnant or non-pregnant, other than all of them had tested positive for COVID-19. The number of women in the sample was very small, moreover.

Why is the research important?

The research findings prompted immediate responses from the PHAS. Sweden also began a joint investigation into the effect of COVID-19 on pregnancy and the fetus/newborn, using data from various national registries.

The paper concludes, “Pregnant women should be cautious considering the potentially severe consequences of SARS-CoV-2 infection and those with additional risk factors such as overweight or obesity, hypertension, and gestational diabetes should take extra precautions.”

Journal reference:
Dr. Liji Thomas

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.

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