Study design and participants
The data were derived from prospective screening for pregnancy
complications in women with singleton pregnancies attending their first
routine hospital visit at 11 + 0 to 13 + 6 weeks of gestation at King’s
College Hospital, London or Medway Maritime Hospital, Kent from March
2006 to November 2020. The visit included recording of maternal
demographic characteristics and medical history, measurement of maternal
weight and height and ultrasound examination for the measurement of the
fetal crown–rump length (CRL) and to determine gestational
age24, measurement of the fetal nuchal translucency
thickness, as part of screening for trisomies25, and
examination of the fetal anatomy for the diagnosis of major fetal
defects26.
Participants completed a questionnaire, which was then reviewed by a
doctor together with the woman. Patient characteristics included
maternal age, racial origin (white, black, South Asian, East Asian, and
mixed), method of conception (natural or assisted by IVF or use of
ovulation drugs), cigarette smoking during pregnancy, medical history of
chronic hypertension, diabetes mellitus, systemic lupus erythematosus
(SLE) or antiphospholipid syndrome (APS), family history of preeclampsia
in the mother of the patient, and obstetric history that included parity
(parous or nulliparous if no previous pregnancies at ≥24 weeks’
gestation), previous pregnancy with PE and previous pregnancy with
delivery of small for gestational age (SGA) neonate with birth weight
<10th percentile of The Fetal Medicine
Foundation fetal and neonatal population weight
charts.27
The inclusion criteria for this study were singleton pregnancies
delivering a non-malformed live birth or stillbirth at ≥24 weeks’
gestation. We excluded pregnancies with aneuploidies and major fetal
abnormalities. Women gave written informed consent to take part in the
study which was approved by the NHS Research Ethics Committee. There was
no patient involvement in the design of the study.