Participants
This was a retrospective study of 2676 deliveries at our institution
from January 2019 to June 2021. In our hospital, when a cesarean section
was necessary (or is considered highly likely), we performed blood tests
(complete blood counts, biochemical tests including kidney and liver
function, coagulation tests, and tests for infectious diseases including
HIV), chest radiography, and electrocardiography as preoperative tests,
within at least one month of delivery. All twin pregnancies underwent
preoperative examinations. After excluding 965 patients (including 959
cases in which blood tests were not performed, three cases of missing
data, and three cases of triplet pregnancy), we finally enrolled
1711 patients pregnant with 1547
singleton pregnancies and 164 twin pregnancies who underwent renal
function tests (serum blood urea nitrogen [BUN], creatinine, and
estimated glomerular filtration rate [eGFR]) within at least one
month of delivery (Supplementary Figure 1). The study conformed to the
principles outlined in the Declaration of Helsinki of 1964. This study
was approved by the Ethics Committee of the Japanese Red Cross Nagoya
Daiichi Hospital, Nagoya, Japan (approval number: 2021-422).