SARS-CoV-2 infection in early first-trimester miscarriages: a prospective observational study

Research question: Is there an association between SARS-CoV-2 infection and first-trimester miscarriage? Design: This multicentre prospective study included a cohort of women with first-trimester miscarriages registered consecutively by seven Spanish hospitals where universal PCR screening for SARS-CoV-2 infection was implemented with both miscarriages and deliveries. The incidence of SARS-CoV-2 infection among women with first-trimester miscarriages was compared with the rate registered in women on admission to the delivery ward within the same time frame using a mixed-effects Poisson regression analysis, considering 'hospital' as random effect. The characteristics of SARS-CoV-2 positive and negative patients who miscarried were compared through two-sided univariable analyses. Results: A total of 301 miscarriages were registered, 11 (3.7%) to SARS-CoV-2 infected and 290 to non-infected women. In the same time frame as the miscarriages, 1936 deliveries were registered, 44 [2.3%] of them were SARS-CoV-2 infected. No differences in terms of SARS-CoV-2 infection incidence were observed between infected miscarriages and infected deliveries (P = 0.233). Regarding the differences observed between miscarriages in SARS-CoV-2 positive and negative women, more inevitable miscarriages occurred in the group of infected women (36.4% versus 16.5% in noninfected women; P = 0.004), and there was greater surgical management of miscarriages (27.3% versus 8.2% in noninfected women; P = 0.036), probably in line with the greater number of inevitable miscarriages observed in this group. Conclusions: No association between SARS-CoV-2 infection and risk of first-trimester miscarriage was observed; however, the type of miscarriage seems to differ between SARS-CoV-2 positive and negative women, with inevitable miscarriage being more frequent among infected women.