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Accompanying a video on MSN News today (17th jan 023) is the following statement :

Pregnant women who catch Covid are SEVEN times more likely to die, warns new research. They are also at a "significantly elevated" risk of being admitted to intensive care and 23 times more likely to develop pneumonia, according to the study published in BMJ Global Health. In addition, the findings suggest that Covid during pregnancy also increases the risk that the baby will need to be admitted to intensive care. Scientists say their findings add urgency to calls for more women of childbearing age to get vaccinated Lead author Professor Emily Smith, of the George Washington University Milken Institute School of Public Health in the US said: “This study provides the most comprehensive evidence to date suggesting that Covid-19 is a threat during pregnancy.

The only recent BMJ Global Health study I can find on the subject does not make any such claim (that I can find) and states :

Taken together, this analysis of 12 studies including 13 136 pregnant women from 12 countries indicates that SARS-CoV-2 infection at any time during pregnancy increases the risk of maternal mortality, severe maternal morbidities and adverse newborn outcomes. These findings underscore the need for global efforts to prevent COVID-19 during pregnancy through targeted administration of vaccines and non-pharmaceutical interventions.

Is this 'seven times' morbidity claim true ?

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    The abstract of the paper you quote mentions a relative risk of 7.68 for mortality in the abstract, which fits to the claim in the MSN article.
    – Mad Scientist
    Jan 17, 2023 at 13:55
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    @NigelJ, you could also post that as an answer to your own question. (I don't think you should delete your question.)
    – Ben Bolker
    Jan 17, 2023 at 14:26
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    7 times more likely than whom? 7 times more likely than pregnant women who do not get COVID? 7 times more likely than non-pregnant women who get COVID? 7 times more likely than dancing bears?
    – shoover
    Jan 18, 2023 at 3:55
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    @shoover as compared with uninfected pregnant women, conclusion being SARS-CoV-2 infection at any time during pregnancy increases the risk of maternal death by 7.68
    – Timmetje
    Jan 18, 2023 at 9:58
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    @CristobolPolychronopolis The mortality of pregnant women in the UK has risen since 2020 by about 2.0%. This is due to Covid-19, as the above study proves.
    – Nigel J
    Jan 19, 2023 at 21:30

2 Answers 2

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An estimate of being roughly seven times more likely to die is a reasonable summary of the information in the paper you linked yourself. The sentence in the abstract is

Pregnant women with SARS-CoV-2 infection—as compared with uninfected pregnant women—were at significantly increased risk of maternal mortality (10 studies; n=1490; RR 7.68, 95% CI 1.70 to 34.61)

The RR 7.68 means that the relative risk is 7.68 higher for pregnant women with a SARS-CoV-2 infection compared to pregnant women without infection. The studies contained a total of n=1490 pregnant women (I'm not sure whether this is the number of women with infection or the total). The last bit means a 95% CI convidence interval for the estimated relative risk is somewhere between 1.70 and 34.61. Hence there is fairly high convidence that the risk is increased but by how much the risk is increased is very uncertain.

Another useful number for context is the general maternal mortality during child birth which in the US is around 20 per 100.000 birth (source). This number of deaths is estimated to be increased by a factor of around 7 due to a SARS-CoV-2 infection.

Edit: JonathanReez claims that the answer should be inconclusive so a here a few more words on what the study claims (and is correct in claiming) and what it doesn't.

First one can compute backwards that with a base rate of maternal mortality of around 20 per 100.000 and an RR of 7.68 comes out to exactly two deaths in their sample of n=1490 (equivalent to an observed maternal mortality of around 150 per 100.000 in the sample).

This turns this into a classical probability problem. The null hypothesis is that there is no effect due to corona. So how likely is it to observe 2 deaths in 1490 women if the maternal death rate is 20 per 100.000? It turns out this probability is smaller than 5% (but bigger than 1%). Hence one can conclude with 95% confidence that women with a corona infection suffer a higher maternal mortality than women without (which is what the study says). We couldn't make the same conclusion with 99% confidence.

Trying to estimate how much bigger the maternal mortality rate actually is is very difficult due to the limited data. The 2 observed deaths lead to an estimate of 7.68 higher than normal but whether the actual increase is more around twice as big or more around 30 times as big cannot be concluded from the data (the study computes this as a 95% confidence that the effect is in the interval [1.70, 34.61]).

Additionally the claim is only saying that women with a corona infection have higher maternal mortality. It does not claim that the higher mortality is due to the corona infection. This could be the case but it could also be the case that there is a confounding factor that increases both the risk of a corona infection and maternal mortality (for example race or poverty). This question cannot easily be answered with the limited amount of data and the study doesn't make any claims in this direction.

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  • I'm trying to think of a way that your first sentence could be improved to include some mention that the "SEVEN times" is only the preliminary number. I feel like people will fixate on that 7x, and if future research shows it as higher or lower people will panic or dismiss the research respectively. Also, does the research do anything to establish cause and effect? I wouldn't be surprised to hear that the increased pregnancy risk is because of risky behaviors that also led them to catch Covid.
    – Rob Watts
    Jan 18, 2023 at 22:32
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    @RobWatts I changed the first sentence. Afaik the study only talks about correlation. I think the number of deaths is (fortunately) way too small to take any more detailed conclusions like trying to look into causes. See also the huge convidence interval on how big the effect actually is.
    – quarague
    Jan 19, 2023 at 6:39
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    @EarlGrey I found numbers by race, with worst = 41 per 100,000 for black women, and best = 11 per 100,000 for hispanic women.
    – gnasher729
    Jan 20, 2023 at 18:13
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    @JonathanReez a) Presumably there are not that many more women in the US that were pregnant and had a covid infection and b) The study did their math correctly. With n=1490 and 2 deaths you can exclude the null hypothesis of no effect due to Covid with 95% confidence (but not with say 99% confidence) but the estimated range of the size of the effect is huge (somewhere between 1.7 to 35 times worse with 95% confidence). As this is a meta study I suppose that is all the data there is.
    – quarague
    Jan 21, 2023 at 10:18
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    Was the risk for pregnant women higher than for non-pregnant women of the same age? Every activity has a risk X, and Covid has a risk Y, and you divide Y by X and say “if you do X then Covid increases your risk by Y/X + 1”. So it could be that if you are pregnant, you should get vaccinated. If you like red wine, you should be vaccinated. If you eat vegan or no vegetables at all. You should get vaccinated. If you usually drive drunk at excessive speed, no need to get vaccinated.
    – gnasher729
    Jan 21, 2023 at 17:49
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The CDC has data on all-cause maternal mortality from 2018, 2019 and 2020:

Year Number of live births Number of maternal deaths Maternal mortality rate
2018 3,791,712 658 17.4
2019 3,747,540 754 20.1
2020 3,613,647 861 23.8

A maternal death is defined by the World Health Organization as, “the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and the site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes”

As we can see from the data, only 0.02% of pregnancies end with a maternal death, so this is a very rare event to begin with. We also see that 2020 wasn't exceptionally bad, as the increase in mortality from 2018 to 2019 (20.1/17.4 = 15%) was similar to the increase in 2020 (23.8 / 20.1 = 18%). COVID might've have had some impact on mortality during pregnancy but it's not easily visible in mortality statistics.

The other answer links to studies that attempt to quantify the relative risks of having a COVID infection but their cohorts are far too small to meaningfully study an event with a 0.02% probability. So I'd say the answer to this question is inconclusive, as we simply don't have enough data to provide a meaningful answer. Compare this to, say, all-cause mortality statistics for people above the age of 65 where there's a clear increased during the pandemic and little argument over the severity of the virus.

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    If you account for the fact that other industrialized countries have a maternal mortality of around 5, other countries much poorer than the US manage values around 20 and these numbers have been decreasing globally for decades, a 15% increase is exceptionally bad, even more so if it happens 2 years in a row. Somewhere the US health care system is failing badly in its maternal care and whatever the reason is, it seems to be getting worse. This is probably unrelated to corona though.
    – quarague
    Jan 21, 2023 at 11:57
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    The pre-vaccine COVID infection fatality rate in the childbearing age cohort was approximately 1/1000. 7x higher risk would be 0.7%. If the COVID IFR for pregnant women was 0.2/1000, pregnancy would be protective against COVID. Using the base maternal mortality rate is incorrect as the comparison is COVID deaths in pregnant vs not pregnant. The speculative math in this answer is therefore entirely incorrect.
    – CJR
    Jan 21, 2023 at 14:16
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    You don't have any idea what the number of infections is, COVID infections in 2020 were between 5-10% of the population and we were protecting vulnerable populations with NPIs. There is a reason that you need to do control-matched studies for this and that you can't extrapolate off the base mortality rate.
    – CJR
    Jan 21, 2023 at 15:37
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    The other study had 38 deaths in the COVID cohort and 3 deaths in the non COVID cohort. You again misinterpreted the abstract because of your misunderstanding of the proper base rate.
    – CJR
    Jan 21, 2023 at 15:52
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    Table 3 - Maternal Deaths is 38/368 and 3/1122 for COVID and non COVID cohorts respectively (a better question would be what is the quality of the underlying studies and if they're stratified but that reanalysis is out of scope here IMO)
    – CJR
    Jan 21, 2023 at 15:56

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