The risk of dying from Covid-19 in pregnancy

Update 2 November. This post was written when there were few reliable estimates. This is no longer the case. For the WHO best estimate click here.

For the facts click here.  This is my interpretation.

It’s not zero, 13/73 (18%) of pregnant women with Covid-19, whose cases made it into the newspapers, died (click here). But this must be an overestimate. Covid may not have caused all the deaths, and there will be selective reporting.

In the scientific papers 16/367 (4%) of women died (click here). These data should be more reliable, in that we can can be confident, at least for the women reported in detail from Iran (S67 & S70), that Covid-19 caused the deaths. The other 7 cases from Brazil and Mexico (S66) include less detail, and some were identified only from newspaper reports, so the cause of death must be in some doubt. There is also a more serious problem. All the deaths were reported in studies of maternal death due to Covid-19. Mothers who survived in the relevant regions were not reported. This must also be an overestimate.

Restricting analysis to the the larger series probably gives a better estimate. In Wuhan 0/109, Netherlands 0/91, Lombardy 0/42, NY Presbyterian/Columbia 0/33 mothers died. In total that’s zero deaths out of 275 pregnant women with Covid-19.

But the death rate can’t be zero. Some women really did die, and many mothers in the larger series were seriously ill and nearly died. In the Whuhan series (S55 here) 9/109 pregnant women had severe disease (hypoxaemia) although only one required ventilation. In the Netherlands 5/91 (S41, here), Lombardy 7/42 (S32 here), & NY Presbyterian/Columbia 2/33 (S41 here), needed intensive care. That’s 14/166 (8%) in total. There have been other reports of pregnant women who were seriously ill (S69, S50, S28, S19, S3 here).

Mortality for non-pregnant people, age 16-49, with Covid-19, who needed intensive care is 24% (ICNARC).  If pregnant women on intensive care had the same mortality, this would correspond to a 2% overall mortality. Not zero. But significantly lower than the biased newspaper rate of 18% or the biased “all scientific reports” rate of 4%.

A two percent maternal mortality rate from Covid-19 is my best guess.

Let’s put this in context. 98% of women who develop Covid-19 in pregnancy will survive. But the background risk of mothers dying in pregnancy these days is only 0.01%. This means the risk of a mother dying, if she gets Covid-19, may be 200 times greater than the background risk in pregnancy.

Covid-19 is a serious disease. Don’t underestimate it.

Jim Thornton

Edited noon 3 May.