The curious impact of COVID on premature births

The causes of prematurity are still largely unknown. From an immunological perspective, pregnancy is a particularly delicate time. It requires a careful balance for our bodies: nurturing a growing foetus (ultimately a "foreign" body), fending off infections, whilst at the same time avoiding an overly strong immune response that could affect the foetus...

The only thing scientists can state with certainty is that to reduce the risk of prematurity, it is important to be in good health, and that smoking as well as gestational diabetes have negative consequences on pregnancy. But beyond that, prematurity often remains multifactorial.

Premature births have drastically decreased worldwide, as studies have shown in India [1], Ireland [2], the Netherlands [3] and Denmark [4].

The most widely cited hypotheses

Among the hypotheses for this decline:

• a reduction in air pollution,
• fewer infections and pathogenic germs circulating, thanks to barrier measures and isolation,
• a reduction in work-related stress or commuting,
• a reduction in activity (particularly standing or physically demanding work), which, when too intense, increases the risk of premature birth,
• an extension of maternity leave, particularly before birth.

The hypothesis of reduced air pollution is currently the most widely cited, as several studies have shown that pollution increases the risk of premature birth [9].

The alternative hypothesis

With COVID, there was also a reduction in prenatal visits and in-person check-ups. Could it be that a certain proportion of premature births were due to medical intervention? As if a reduction in care and diagnoses had led to fewer treatments and interventions — and paradoxically had also led to an increase in full-term pregnancies. The hypothesis is that the absence of follow-up may have led to fewer unnecessary interventions, when sometimes doing nothing proved to be the best course of action…

More to follow!

This phenomenon should not overshadow the fact that COVID infection remains problematic in pregnant women, due to the increased risk of premature birth and the risk of developing severe forms of the illness.

In an American study published in November 2020, it appears that the rate of premature birth was higher in these pregnancies (12.9% versus the usual 10.2%) [10].

Another study of 400,000 women aged between 15 and 44, who were pregnant, COVID-19 positive and symptomatic [11], showed that pregnant women were at greater risk of developing severe forms of the illness.

One hypothesis is that pregnancy brings about physiological changes that would increase the risks (changes in immune response, reduced respiratory capacity, higher risk of blood clots or thrombosis...).

No need to panic, though — just be extra careful when pregnant!

If you'd like to explore the topic of immunity further, read our article onBreastfeeding and immunity.