Two kinds of pregnant patient with COVID, and only one was ill from it

Early in the pandemic, "pregnant women hospitalised with COVID-19" covered two
very different situations, and counting them together obscured both.

• Women admitted because of COVID-19 — worsening respiratory status
• Women admitted for pregnancy-related treatment or procedures, such as
  delivery, who were found to have COVID-19 on routine testing

This study, across eight US health care centres, 1 March – 30 May 2020,
separates them.

The outcomes for the first group

Nearly a third into intensive care. That is the figure that describes the
disease, and it would be diluted to a much smaller number if the women admitted
to give birth were counted alongside.

And the risk factors that distinguished them

**Prepregnancy obesity and gestational diabetes were more prevalent among the
women admitted for COVID-19** than among those admitted for pregnancy care who
happened to test positive.

Same virus, same weeks, same hospitals — and the ones who became ill enough to
be admitted for it were more likely to have those two conditions. That is what
a risk factor looks like when the comparison group is well chosen: the second
group functions as a sample of pregnant women with SARS-CoV-2 who were not
hospitalised for it.

Why the distinction had to be made deliberately

Universal testing on labour wards was becoming standard in 2020, which meant
hospitals began detecting asymptomatic infection in every woman who came in to
give birth. Those cases entered the same surveillance counts as the women in
intensive care.

Without separating them, the apparent severity of COVID-19 in pregnancy falls
as testing expands — not because the disease changed, but because the
denominator did. **"Reason for admission" is the variable that keeps the
numbers honest**, and it is the same distinction COVID-NET built into its
hospitalisation surveillance for the same reason.

Pregnant women might be at increased risk of severe illness from SARS-CoV-2,
and this is one of the early studies that could say so with a comparison rather
than an impression.

Source: Centers for Disease Control and Prevention, MMWR.