“The causes of preterm birth have been so elusive, despite considerable efforts,” said Dr. Denise Jamieson, an obstetrician at Emory University’s School of Medicine in Atlanta who was not involved in the new study. Even though the global study found a dip of only about 4 percent, “I think any reduction in preterm birth is noteworthy and important,” she said.
“The next step is to really look at the why,” Dr. Jamieson added.
Dr. Azad and Dr. Roy Philip, a co-author of the new paper and also the Irish neonatologist at University Maternity Hospital Limerick who in 2020 found a striking drop in very early births at his hospital, both said it was possible that lockdowns had quite different effects on different groups of people. A pregnant person like Ms. Becker who was able to stay home in a low-stress environment, with good support, might have benefited. A frontline worker without health insurance might have had a different experience.
In this way, the findings highlighted how much is still unknown about what causes preterm birth. “Even if there are 52 million births in the study, it is not going to immediately answer all the questions,” Dr. Philip said. “But at least this should trigger people to look more closely at what is ideal during pregnancy.”
The study also highlighted the uneven preterm birthrates across different countries. Across the five years of data, the United States had the highest preterm birthrate of any high-income nation included — just shy of 10 percent. Finland’s rate, by contrast, was below 6 percent.
The disparity isn’t surprising, Dr. Jamieson said. “Unfortunately, the United States is an outlier for a lot of important maternal and infant health outcomes when you compare it to other high-income countries.”
Future research could use this global data set to investigate such variations in maternal health. Dr. Azad said she had originally hoped to dig into the drivers of preterm birth during lockdown, not just its frequency: Were changes in air pollution correlated with changes in early births? What about hygiene, or income, or access to health care? But she lacked funding to investigate further, Dr. Azad said, and now those other projects that were deferred early in the pandemic have caught up with her and her colleagues.
Dr. Azad doubts one of her tweets today could launch a huge international research effort. People in spring 2020 had “this burning desire to do something, to either help the pandemic or make something of it,” she said. Some researchers even worked on the project without pay. “I’m a scientist; I don’t like using the word ‘magical,’” she said. “But it was kind of magical.”
Now the mysteries of preterm birth will have to wait for other investigators, Dr. Azad said, adding, “We don’t all have that extra time anymore.”