Study design and population
This was a retrospective observational study of all pregnant women who booked for antenatal care and delivery at University College London Hospital NHS Foundation, UK, between March 2019 and December 2022. The inclusion criteria for this study were singleton pregnancies resulting in the livebirth or stillbirth of an infant without any serious congenital anomalies at ≥ 24 weeks gestation. We excluded patients who declined first trimester combined screening testing (CST) for trisomy 21, 13 and 18, since PAPP-A results were not available for this cohort. We also excluded those who did not have a BP recorded from their booking visit and those who were lost to follow-up. Data on maternal characteristics and pregnancy outcomes were collected from the hospital maternity records. Gestational age was determined by crown–rump length (CRL) measurement performed at the 1st trimester scan between 11+2 to 14+1weeks.
Standard care, using the NICE guidance, identified women at their booking midwifery or Obstetric appointment as high risk of developing PE if they had any one major factor (hypertensive disease in previous pregnancy, chronic kidney disease, autoimmune disease, diabetes mellitus or chronic hypertension) or any two moderate factors (first pregnancy at age ≥ 40 years, interpregnancy interval > 10 years, body mass index at first visit ≥ 35 kg/m2 or family history of PE). The current recommendation by NICE is that all women who screen positive by this method should be offered aspirin prophylaxis of 150mg until 36 weeks’ gestation. Subsequent pregnancy management including the need for third trimester fetal growth surveillance or need for earlier induction of labour was scheduled as recommended by NICE.12 Maternal serum PAPP-A was measured in those who consented to CST. Only those with MAP taken according to standardised protocols by midwives or healthcare assistants were included in the study.
PE was defined according to the International Society for the Study of Hypertension (2014) guidelines by having, in addition to hypertension, at least 1 of the following problems: renal involvement (proteinuria 300 mg/24 h and/or creatinine 90 mmol/L or 1 mg/dL), liver impairment (transaminases >70 IU/L), neurologic complications (e.g. eclampsia), thrombocytopenia (platelet count <150,000/mL), uteroplacental dysfunction (e.g. fetal growth restriction).13 In addition, according to gestational age at diagnosis, PE was subdivided into preterm PE with onset at <37 weeks’ of gestation and term PE with onset beyond 37 weeks. SGA was defined as birthweight <5thpercentile for gestational age.14