Birth rates in Canada and the United States dropped sharply in March 2020, months before any lockdown baby bust could have shown up, and the drop did not happen in comparable European countries. Two statisticians argue the missing babies belonged to people who would have flown in from abroad to give birth, and they use the gap to put a first number on how common such births are.
The study, by Amit N. Sawant and Mats J. Stensrud of the Chair of Biostatistics at the Ecole Polytechnique Fédérale de Lausanne in Switzerland, was published online in the American Journal of Epidemiology on August 19, 2024 (read the paper).
A natural experiment in closed borders
Almost everyone who gave birth in mid-2020 had conceived before COVID-19 was on anyone’s radar, so family planning in response to the pandemic cannot explain a fall in births between March and November 2020. Effects of lockdowns on conception would only appear around 38 weeks later, from December 2020 onward, and that is exactly when European countries saw their dip.
What did change at once was travel. Between March and June 2020, international air travel fell by almost 98% compared with a year earlier, and land borders closed too. Expatriates, international students, new immigrants and others who planned to give birth in North America were stuck. The authors call them incoming individuals.
The researchers gathered monthly live births from January 2016 to December 2021 for Canada, the US and European countries. They used two methods built on different assumptions: an interrupted time series, which compares each country with its own seasonal trend, and a difference-in-differences analysis, which compares Canada and the US with European countries whose birth trends had moved in parallel before the pandemic, namely Austria, Belgium and Slovenia.
Thousands of missing births a month
The time series analysis estimated that Canada had about 8,700 fewer births than expected between March and November 2020, and the US about 60,000 fewer. Per month, that is 970 births in Canada, or 3.2% of all births, and 6,700 in the US, or 2.2%.
The comparison with Europe gave similar answers: declines of 2.8% in Canada and 3.4% in the US over the same months. The shortfall persisted through 2021, at 2.6% in Canada and 3.5% in the US, even after the post-lockdown baby boom.
The authors tested other explanations. Changes in preterm births and stillbirths were far too small to account for the drop. Abortions in the US rose by about 15,000 in 2020, in line with an existing upward trend. A jump in Canadian abortion numbers came with a change in how they were counted, so the data could not explain the decline either.
As a check, they looked at Hong Kong, a known destination for birth tourism from mainland China. Births there fell by 40% in 2013 when anti-birth-tourism quotas came in, and by 23% from March to November 2020.
What the estimate can and cannot say
The authors list limits. Not all travel stopped, and some migrants may have left North America during the pandemic, which could also lower births. On the other hand, residents who would normally travel elsewhere to give birth were also stuck, which would make their 2% to 3% estimate conservative.
Until now, they write, the share of births to recent international arrivals had been “unknown and infeasible to study.” A border closure nobody planned turned it into a measurable number: roughly one birth in every 30 to 50.
Study Details:
- Title: Explaining the sharp decline in birth rates in Canada and the United States in 2020
- Authors: Amit N. Sawant, Mats J. Stensrud
- Journal: American Journal of Epidemiology
- Publication Date: August 19, 2024
- DOI: 10.1093/aje/kwae274