Study population and design
The data for this study were derived from prospective screening for
adverse obstetric outcomes in women attending for routine pregnancy care
at 19+0-24+6 weeks’ gestation at
King’s College Hospital and Medway Maritime Hospital, UK, between 2011
and 2020. In this visit we first, recorded maternal demographic
characteristics and medical history as self-reported by the patients,
second, carried out an ultrasound examination for fetal anatomy and
measurement of fetal head circumference, abdominal circumference and
femur length to calculate the EFW by the Hadlock formula9, because a systematic review identified this as
being the most accurate model 10, and third, measured
the left and right UtA-PI either by transvaginal or transabdominal color
Doppler ultrasound and calculated the mean value of the two arteries11,12. The majority of UtA-PI measurements were
carried out transvaginally because at the same time we were measuring
cervical length; the transabdominal approach was used when women
declined transvaginal sonography. Gestational age was determined from
measurement of fetal crown-rump length at 11-13 weeks or the fetal head
circumference at 19-24 weeks13,14. The same study
population was used for development and validation of the model based on
multivariable logistic regression analysis for prediction of placental
dysfunction related stillbirth1.
The inclusion criteria for this study were singleton pregnancies that
delivered a phenotypically normal live birth or stillbirth at> 24 weeks’ gestation. We excluded pregnancies with
known aneuploidies, major fetal abnormalities, those ending in a
miscarriage or termination of pregnancy. There was no patient
involvement in the design of the study.