Curious scenario of changes in incidence of preterm births during COVID-19 pandemic. Pointers for future research?

Dear Editor,

Preterm births (PB) have always baffled researchers across the world and the exact etiopathogenesis is still unknown. However, the major risk factors for PB include intrauterine infection, medical disorders complicating pregnancies like diabetes and hypertension, antepartum hemorrhage, and maternal or fetal stress [1]. There are several other factors including environmental exposure such as air pollution and lifestyle factors which could also play a role [1].

A prospective observational study on perinatal outcome from Nepal done from nine referral hospitals from January to May, 2020 reported raising PB during COVID-19 related lockdown period when compared to pre-lockdown times [2]. Authors have hypothesized that increase in PB could be due to distress of COVID-19-related social restrictions and psychosocial stress during pregnancy [2]. Reduction in number of total institutional deliveries, overcrowding and increased proportion of high risk deliveries could have played a role. This is however in stark contrast with data coming out from developed nations [[3], [4], [5]]. Ever since the COVID-19 pandemic broke out in early 2020, NICUs from developed nations started observing a peculiar trend of reduction in the number of preterm births (PB) [3]. There were independent news reports from NICUs of Australia, Canada, USA, Ireland and Denmark and now is quickly becoming a global phenomenon in developed nations [[3], [4], [5]]. Researchers from Denmark found that the number of premature infants born < 28 weeks gestation had dropped by a staggering 90 percent compared to pre-COVID times [3]. In Calgary, Canada, the PB less than 32 weeks gestation has approximately reduced by 40 % and PB with birth weight of < 1 kg has fallen by 50 % [4]. A 73 % reduction in the rate of VLBW deliveries was found in Ireland when compared to pre-COVID data [5].

The reduction in PB could be attributed to the cumulative influence of socio-environmental factors related to COVID preventive measures on pregnant mothers. The most plausible explanation could be the overall reduction in infectious diseases during COVID pandemic. This can be attributed to the strict lockdown measures enforced in most countries along with increased public health awareness and practice of personal hygiene (social distancing, use of face mask, hand sanitizers) and environmental hygiene (Clean water, Food hygiene, Housing sanitation, school/public place/workplace sanitation). Another major contributing factor would be the reduction in stress levels, as most pregnant women are either ‘not working’ or ‘working from home’ during this pandemic contributing to reduction in ‘work’ related stress. Air pollution, a definite risk factor for PB, has reduced during this COVID-19 lockdown period [1]. Other possible contributing factors could be reduction of access to addictive substances, increased time for personal care, more time with family members, restricted travel, reduced time spent outdoors, reduced in-person hospital visits etc. There is enough evidence linking the factors like infection, stress and pollution to PB [1].

These conflicting observations are based on the early trends which might change as the pandemic progresses. There is a possibility of reversal in this trend when lockdown restrictions are lifted. It is extremely important to study this conflicting data from developed and developing nations in detail to understand the pathogenesis of ever-puzzling PB and to develop possible prevention strategies.

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Contributions

TA and VS conceived the concept. TA and VS reviewed the literature and drafted the initial version of the manuscript which was critically reviewed by VB. All authors contributed to drafting of the manuscript and approved the final version of the manuscript. VB shall act as guarantor of the paper.

Funding source

None.

Declaration of Competing Interest

None declared.