National population prevalence of antibodies to SARS-CoV-2 among pregnant women in Scotland during the second wave of the COVID-19 pandemic: a prospective national sero-survey

McAuley, Andrew; Gousias, Petros; Hassan, Taimoor; Rashid, Lorna; Richardson, Claire; Reid, Graham; Templeton, Kate; McGuire, Jacqueline; Wise, Helen; McVicar, Louise; Jenks, Sara; Gunn, Robyn; Dickson, Elizabeth; Stock, Sarah J.; Stockton, Angela; Waugh, Craig; Wood, Rachael; McMenamin, Jim; Robertson, Chris; Goldberg, David J.; Palmateer, Norah E.

Objectives To determine SARS-CoV-2 seroprevalence among pregnant women in the Scottish population during the second wave of the COVID-19 pandemic. Study design/Methods: We tested 13,428 residual samples retrieved from pregnant women participating in first trimester combined ultrasound and biochemical screening for fetal trisomy (CUBS) across Scotland for SARS-CoV-2 antibodies over a 6-month period from November 2020-April 2021. Seroprevalence estimates were adjusted for the sensitivity and specificity of the assays and weighted to reference populations. Results Seroprevalence rates in the antenatal samples significantly increased from 5.5% (95% CI 4.7%-6.5%) in the 5-week period up to and including ISO week 51 (w/b Monday 14th December 2020) to 11.3% (95% CI 10.1%-12.6%) in the 5-week period up to and including ISO week 14 (w/b Monday 05th April 2021). Increasing seroprevalence trends across the second wave were observed among all age-groups. Conclusions By the end of the second wave of the COVID-19 pandemic, around one in 10 women tested around the end of the first trimester of pregnancy had antibodies to SARS-CoV-2 suggesting that the vast majority were still susceptible to COVID-19 as they progressed to the later stages of pregnancy, when risks from infection are elevated for both mother and baby.