Analysis of data from the UK and US registries of pregnancies with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection shows that preterm delivery occurred in a higher proportion of women with SARS-CoV-2 infection compared to contemporaneous and historical national data. Meanwhile, the proportions of pregnancies affected by stillbirth, a small-for-gestational-age infant or early neonatal death were comparable to those in historical and contemporaneous UK and US data.
The study, published in Ultrasound in Obstetrics and Gynecology, used data from the UK and global Pregnancy and Neonatal outcomes in COVID-19 (PAN-COVID) registry and the US American Academy of Pediatrics Section on Neonatal Perinatal Medicine (AAP SONPM) National Perinatal COVID-19 registry.
The study team looked at data of 4,005 pregnant women with suspected or confirmed SARS-CoV-2 infection. Of these women, 1,606 were from the PAN-COVID registry, which includes pregnancies with suspected or confirmed maternal SARS-CoV-2 infection at any stage in pregnancy, while 2,399 were from the AAP SONPM registry, which includes pregnancies with positive maternal testing for SARS-CoV-2 from 14 days before delivery to 3 days after delivery. All the women gave birth between January and August 2020.
“Pregnant women should be counselled that SARS-CoV-2 infection increases the risk of preterm delivery but not stillbirth, early neonatal death or a small baby,” wrote Edward Mullins, Imperial College London, London, UK, and colleagues. “Healthcare providers should recommend SARS-CoV-2 vaccination in pregnant women and women planning pregnancy, alongside enhanced social distancing.”
The researchers found that preterm delivery occurred in 12.0% of all women in PAN-COVID, in 16.2% of those women with confirmed infection in PAN-COVID and in 15.7% of women in AAP SONPM, which they noted was 60% higher in PAN-COVID than is expected for England and Wales based on the Office of National Statistics (ONS) data for January-September 2020 (7.5%), and 57% higher in AAP SONPM than expected based on US National Vital Statistics Reports for 2018 (10%). The majority of preterm deliveries occurred between 32+0 and 36+6 weeks’ gestation. Meanwhile, spontaneous onset of pre-term labour followed by preterm vaginal delivery occurred in 2.5% of all women in PAN-COVID, in 3.5% of those with confirmed infection and in 3.7% of those in AAP SONPM.
“As the proportion of women with spontaneous labour and preterm vaginal delivery was low, a high proportion of preterm deliveries may have been due to physician concern about adverse effects of SARS-CoV-2 infection on the maternal or fetal condition,” the authors explained.
On the other hand, neither registry reported any neonatal deaths attributable to SARS-CoV-2 infection. The proportion of pregnancies affected by early neonatal death, noted the authors, was no higher than would be expected based on England and Wales ONS data (0.2%) or the US CDC data (0.38%). Similarly, the proportion of pregnancies resulting in stillbirth (1 in 200) was comparable to that reported in a UK population surveillance study (5.64 per 1,000 total births), slightly greater than that reported in provisional ONS data for January to September 2020 (0.39%), and comparable to that reported in the US National Vital Statistics System data (611.7 per 100,000 live births).
In both registries, the authors reported that suspected or confirmed SARS-CoV-2 infection resulted in fewer than 10% of babies being born small for gestational age and did not change the expected distribution of birth weight z-scores.
Meanwhile, the researchers found that maternal deaths related to suspected or confirmed SARS-CoV-2 infection were uncommon in both the PAN-COVID and AAP SONPM registries, with the rates of 0.50% in all women in PAN-COVID, 0.46% in those women with confirmed infection and 0.17% in women in AAP SONPM. Nonetheless, they pointed out that the rate was higher than expected based on UK and US population data, which was likely explained by underascertainment of women affected by milder or asymptomatic infection in pregnancy in the PAN-COVID registry although not in the AAP SONPM registry.
“The data presented support strong guidance for enhanced precautions to prevent SARS-CoV-2 infection in pregnancy, particularly in the context of increased risks of preterm delivery and maternal mortality, and for priority vaccination of women planning pregnancy,” the authors concluded.