The causes of premature, or preterm, birth have long been a medical mystery. But this year, amidst a raging pandemic, the international medical community reported a curious phenomenon: preterm births drastically declined around the world. Now researchers are scrambling to understand what has caused this decline in the hopes of finally understanding the intricacies of preterm birth.
One of these researchers is Jennifer Culhane, an associate research scientist for Yale’s School of Medicine. Culhane and her colleagues are currently running a large-scale study focused on the decline in preterm births specifically in the U.S. during the COVID-19 lockdowns. We talked to Culhane about her research work and why preterm birth continues to be such a mystery.
Despite the fact that we live in a world with amazing medical and technological advances, we still know very little about preterm birth. Why is it so hard to understand its causes?
It is a complex and relatively common disorder. There is not one thing that leads to preterm birth. It’s not just one big river, there are lots of tributaries which makes it complicated. Preterm birth is also what we call idiopathic. This means you can’t put your finger on a precise explanation. And it’s extremely difficult to fix a problem when you do not understand its origins.
The immunology of pregnancy is still a field that has lots of room to grow. If you think about it, pregnancy is an exquisitely complicated moment for the immune system because you basically have what we call an allograft, or a foreign body growing in someone else’s body. It is this finetune balancing act between permitting this allograft [the fetus] to grow, warding off infection, and not having an aggressive immune response that would be harmful to the fetus. [Pregnancy] is really an amazingly complicated system.
Many areas of research that focus solely on issues related to women’s health can have trouble finding funding. Do you think that sexism is part of the reason why there is a lack of funding for preterm birth research?
I would absolutely endorse that idea though I don’t have these facts at my fingertips. For example, look at the funding for the National Institute of Child Health and Human Development (NICHD) compared to the National Cancer Institute. I think that, yes, there is probably a degree of sexism in this whole thing. We have lagged seriously behind in overall understanding of pregnancy physiology. And I would venture to say that we really have no effective treatments for these types of preterm births.
In our recent history, we have not had a breakthrough that has led to a consistent understanding [about preterm birth]. And way more importantly, we haven’t seen any movement in the racial and ethnic disparity in that rate. Black women still have unacceptably higher rates of adverse birth outcomes, like prematurity, compared to white women.
So there is a lot the medical community still doesn’t know about preterm birth. But what do they know about decreasing the chances of preterm birth?
Be healthy. We know that cigarettes and diabetes are very bad during pregnancy. So control your blood sugar and no cigarettes, that’s pretty much all we know.
This summer medical practitioners from countries around the world including India, Nepal, Ireland, and Denmark recorded a significant decline in preterm births. What can you tell us about this phenomenon?
To clarify, we’re not talking about pregnant women that had COVID. We actually think we see worse reproductive outcomes among COVID positive pregnant women, especially symptomatic ones. We’re talking about some consequence of the COVID era that has broadly influenced the health of pregnant women. It’s really fascinating if it’s true. But I am not 100 percent convinced yet.
There’s been a lot of speculation [about this year’s declines in preterm birth rates] including: a reduction in air pollution, to people touching each other less (meaning there is less communication of all other infectious things like colds), to a reduction in stress.
There’s also this other interesting idea that, during COVID, the amount of prenatal care visits that women were having—the face to face visits—went down a lot. Could it be that a certain proportion of preterm births are what we might call iatrogenic [meaning it is caused by medical treatment]? It’s something to explore as well, whether a reduction in the amount of diagnostic work in pregnancy led to less intervention, which paradoxically, could have led to better birth outcomes. Sometimes doing nothing is better.
I have not heard of other hypotheses to date, but the point is that nobody knows. So what we’ve learned in the past year is…nothing. Because we don’t yet know if this is a real reduction in the rate of preterm birth in the COVID era. Exploring the epidemiology of what’s going on is critical.
And that is exactly what you and your team are doing now. You are currently working on a research study focused on the decline in preterm birth in the US during COVID-19 lockdowns. Can you tell us more about this study and what you are hoping to learn?
We are working with big insurance companies to look at the data and to look at the rates of preterm birth in some of the socio-demographic characteristics of women. We’re also looking at things like changes in clinical care.
We will get down this road in two ways: we will be able to confirm whether or not there is a reduction in preterm birth rates and we can look at who these changes affected. Did [preterm birth rates] go up or down differently by race, ethnicity, or insurance status? We can look for care patterns that changed during COVID. From there, we can attempt to look at the association between those patterns in care and the risk of preterm birth.
We have to be really modest about what we know and what we don’t know. Something large changed, everybody knows this. People behaved and lived differently for the most part. But studying these things is really hard.
What is the most important goal you have when it comes to better understanding preterm birth?
The immunology of pregnancy is hugely important. That one is going to help [the medical community] enormously. But we also really want to know why black women have such high rates [of preterm birth]. We still don’t understand why this is happening so that would be my holy grail. I want to know what is underpinning this racial and ethnic disparity. In this country we have a ridiculously high rate of preterm birth and a totally unacceptable racial disparity in preterm birth.
This interview has been edited and condensed for clarity.