I'm back! Today: COVID Pregnancy, Again

(Toddler teeth next time...)

I’m back. I feel energized. Lots of ups and downs last week but Saturday was a good day. There is a lot to be done, but I hope we can start to move forward. For those of you who were disappointed with the outcome, I hope we can all find a way to come together.

I promised toddler teeth last week and I’m on it, but for Thursday. I wanted, today, to address a new study on pregnancy and COVID that many of you emailed about. And I thought it was also a good time to step back and talk through some of the bigger picture questions people are sending about whether this is a good time to get pregnant.

New CDC Study on Pregnancy

A couple of weeks ago, a new study was released from the CDC on pregnancy and COVID-19, which made for somewhat scary reading and headlines. The basic conclusion was symptomatic pregnant women were more likely to have serious complications — including death — from COVID-19. You can see the study here.

Before we talk about what we should conclude from this particular paper, it is useful to take a step back to ask what we knew before. I’ve talked this through in the past (see here and here) and we have a long entry at COVID-Explained. In general, the risk of COVID-19 infection in pregnant women seems to be similar to comparable non-pregnant women. There does not seem to be any sizable risk to infants, although there is some evidence of slightly increases in prematurity among symptomatic women (although there is also evidence that the pandemic has decreased rates of preterm birth in general).

What is true is that being pregnant puts you in a higher risk category in general and for related diseases (for example, the flu) pregnant women are at higher risk for serious illness. Prior to this paper, we had some evidence suggesting slightly elevated risks of serious illness for symptomatic pregnant women with COVID-19. This risk elevation seemed to be small; smaller than, for example, the seasonal flu.

This new study is, mostly, consistent with this. What the authors do is use data on about 409,000 women with symptomatic COVID reported through the CDC Notifiable Disease system. About 6% of these women were pregnant. The authors compare outcomes for women who are pregnant and those who are not — including hospitalization, need for ventilation and death — and find slightly elevated risks in women who are pregnant. The differences appear in some groups and not others; they are apparent largely in Hispanic and Black women, and in older mothers.

This paper cannot say anything about the risk of COVID-19 infection in pregnant women, since the entire sample includes those with symptomatic COVID-19. Nor can they speak to asymptomatic disease. Their analysis is focused on symptomatic cases, and the question of whether conditional on being symptomatic, pregnant women are higher risk.

What this paper adds to existing work is a very large sample size. What it lacks, though, is a representative sample and complete data. This starts at the top: in their data there are 1.3 million women of childbearing age, but pregnancy status is only collected for 400,000 of them. It’s unclear why only these women.

Perhaps more problematic, many observations are missing variables. And I mean many. For example: One of the outcomes analyzed is ICU admission; this variable is missing for three quarters of the sample. On another outcome — need for more invasive ventilation — the data is missing for 80% of women. Even for death, a quarter of the sample is missing data. In all of these cases there are at least some differences in the degree to which the data is missing across pregnant versus non-pregnant women.

The authors deal with the missing data by imputation. Basically, they assume the variables are zero in most cases if they are missing. If we do not observe if someone had invasive ventilation or died, they assume they did not. That’s probably right most of the time, but it isn’t likely to be right all of the time, and since their effects are small…this could really matter.

I also worried about some aspects of the analysis. When the authors look at the relationship between pregnancy and various outcomes, they adjust for age, ethnicity and a couple of health issues. But, notably, they do not adjust for differences in severe obesity, which is much more common among the pregnant population and we know is a very significant COVID-19 risk factor.

Overall, this paper’s conclusions do not differ much from what I think we might have expected, but given the data quality I’m not sure I think we learn much at all. If anything, we can say that pregnancy is a time to be more careful about all illness. But this shouldn’t cause you to panic.

Should I get Pregnant?

Throughout the pandemic, people have asked me variants of the question “Should I get pregnant now?” In March, it was “Should I wait until June?” In the summer, it was “Should I wait for a vaccine?” Now, we’ve moved to “If I’m pregnant, maybe I cannot get the vaccine, so I should wait? Or not wait?”

Let me start quickly with the vaccine question. A number of people have raised concerns that pregnant women will be left out of vaccination since the vaccine trials typically do not include them. Similar concerns have been raised with children. What if we get a vaccine and we haven’t tested it in kids and pregnant women so they are excluded while everyone else gets in?

I think this concern is overblown. When a vaccine is approved, young women and children will not be at the front of the line, pregnant or not, given their low risk. And we will not be in a position to vaccinate everyone right away. While we are busy vaccinating older adults, there will be time for safety evaluations in other groups. In the end, I doubt pregnant women will much behind everyone else (and they could be ahead). So, let’s put this concern aside.

But even without this, the question remains. At the risk of being a broken record, allow me to suggest you consider first “Framing the Question”. In many ways, I think this is the key step in this decision. What does waiting really mean? Does it mean next month? Six months? A year from now?

Hysterical media rhetoric around results like the above notwithstanding, we are starting to get something of a clearer picture around COVID-19 and pregnancy. It doesn’t seem to be like Zika, or SARS or MERS, where there were key pregnancy-specific risks associated with infection. On the other hand, pregnancy during the pandemic is going to have its challenges — certainly, obstetric care will not look quite the same — and illness risks should always be taken with more caution when pregnant. Put simply: if you had to pick whether to be pregnant during the COVID-19 pandemic or at another time, you’d pick the other time. But if this is the right time, the pandemic shouldn’t rule it out.

The reason timing matters so much is that the COVID-19 pandemic is not going to be over, like, next week or even next month. Even if we have an approved vaccine by the end of the calendar year, widespread availability will be slower and it is simply going to take time for things to get back to normal. If your choice is to try to get pregnant now or three months from now, I don’t expect things will look very different (they could be! I just think it’s not something we’d predict).

On the other hand, if you’re thinking about now versus three years from now, it seems more likely things will be different. Most of us are not thinking pregnancy on that time frame, but some are.

The decision to try for a baby (or try for another one) is never very easy. Even in the absence of COVID-19, there may always be reasons to try now, and reasons to wait. And even once you try, it doesn’t always work out with the timing you expected. COVID-19 is going to be part of the equation, but not the whole thing.

(Oh, and if you do decide to go for it, I have a book for that!)


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