Low placental weight and altered metabolic scaling after severe acute respiratory syndrome coronavirus type 2 infection during pregnancy: a prospective multicentric study.

OBJECTIVES

A higher risk for adverse pregnancy outcome is associated with SARS-CoV-2 infection, which could be partially explained by an altered placental function. Since histopathology is often unspecific, we aimed to assess placental weight, birthweight/placental-weight (b/p) ratio and the metabolic scaling exponent ß, an indicator of a normal fetal-placental growth, in order to analyze the placental function.

METHODS

We included 153 singleton pregnancies with SARS-CoV-2 positive PCR in our study, who delivered at three referring hospitals in Switzerland. Placental weight and b/p ratio were compared to published reference charts. Logistic regression analysis investigated the role of time of infection and other confounding factors on placental weight. The scaling exponent β was compared to the reference value of ¾.

RESULTS

Placental weight was inferior or equal to the 10th centile in 42.5%(65/153) and to the 3rd centile in 19%(29/153) of the cases. The risk of low placental weight was not influenced by the trimester of infection. B/p ratio was >50th centile in 80.4%(123/153) of the cases. Incidence of fetal growth restriction, preeclampsia and gestational diabetes was 11.8%(18/153), 3.3%(5/153) and 19.6%(30/153). Linear regression modelling revealed a pathologic metabolic scaling exponent β of 0.871±0.064 (R2=0.56).

CONCLUSION

SARS-CoV-2 during pregnancy was associated with a higher incidence of low placental weight, an increased b/p ratio and an abnormal scaling exponent β in our cohort. This could be particularly relevant for the yet controversial issue of increased stillbirth rate in SARS-CoV-2 infection during pregnancy. In this regard, intensified fetal surveillance should be mandatory in these pregnancies.