INTRODUCTION
The relationship of SARS-CoV-2 and pregnancy has been under study since the outset of the coronavirus pandemic. Evidence shows that pregnant women with COVID-19 are at an increased risk of severe pregnancy complications, including preeclampsia (PE), admission at the intensive care unit, preterm birth or maternal mortality1.
One of the first studies about COVID-19 and pregnancy, published in February 2020, suggested an increased PE incidence amongst pregnant women with COVID-192. This was confirmed in a systematic review published online in March 2020, where a PE incidence of 14.6% was observed in pregnant women with COVID-193, as compared with 2-8% in the general population4. INTERCOVID, a prospective comparative study matching pregnant women with and without COVID-19, showed that the risk of developing PE/eclampsia was almost 4 times greater in women with COVID-191. Subsequent analysis of the same population examining PE incidence showed a risk ratio of 1.95 (95%CI: 1.38-2.75)5. Recently, a large meta-analysis that included 28 studies showed an increased PE incidence risk, with an odds ratio of 1.62 (95%CI: 1.45-1.82)6.
Different theories have been suggested regarding the association between PE and COVID-195–9. One of them hypothesises that PE and COVID-19 are associated due to sharing risk factors for endothelial damage, such as obesity, hypertension, diabetes and maternal age. In that case, PE in the preclinical stage could be an additional risk factor for endothelial damage, thereby increasing the risk of developing COVID-19, mostly in its severe forms. The question is whether preexisting endothelial damage due to abnormal trophoblastic invasion increases the risk of developing COVID-19 and its severity, or whether the association between both conditions is driven by the fact that COVID-19 and PE share risk factors increasing the risk of both conditions. If preexisting endothelial damage due to abnormal trophoblastic invasion10 makes patients more vulnerable to COVID-19 (or more likely to develop a severe form of COVID-19), women with COVID-19 would have lower placental growth factor (PlGF) levels and increased mean uterine artery pulsatility index (UtAPI) as compared to the reference population.
The primary aim of this study was to examine baseline risk factors, as well as biochemical and biophysical markers measured in the first-trimester combined screening for PE in pregnant women with COVID-19 versus the general population. The secondary aim was to compare these baseline characteristics and markers between women with mild and severe COVID-19.