Population
We included women with pre-eclampsia and normotensive pregnancies who
were recruited to the PROVE biobank and database at Tygerberg Hospital,
Cape Town, South Africa. Tygerberg Hospital is a referral hospital that
manages only high-risk pregnancies and delivers over 7000 women a year.
The PROVE biobank is an ongoing collaborative project that recruits
women with pre-eclampsia and control pregnancies to facilitate research
in the field of pre-eclampsia and in particular pre-eclampsia with
severe features, focusing on eclampsia and pulmonary oedema. The study
is registered with ISCRTN, registration number ISRCTN10623443. PROVE
collects the recommended predictors and core-outcome sets recommended by
CoLab to facilitate data sharing in preeclampsia
research.11
For this study, we included women with singleton pregnancies who were
able to speak and understand English, Xhosa or Afrikaans. Exclusion
criteria included known neurological or cardiac disease. For
normotensive women, additional exclusion criteria were chronic
hypertension and diabetes mellitus. We included women with eclampsia,
pulmonary oedema (as an example of pre-eclampsia with severe features),
pre-eclampsia without complications and normotensive pregnancies.
Pre-eclampsia was defined according to the NICE
guidelines.12 Eclampsia was confirmed when
pre-eclampsia was complicated by generalized tonic-clonic seizures in
the absence of another etiology. Pulmonary oedema was diagnosed when
there was worsening dyspnea, fine bibasal inspiratory crackles on
auscultation and features of pulmonary oedema on chest x-ray. Women were
considered to have pre-eclampsia without severe features if they did not
meet the NICE guidelines classification of severe
pre-eclampsia.12 Pregnancies were considered to be
normotensive if the women consistently had a systolic blood pressure
below 140 mmHg and a diastolic blood pressure below 90 mmHg during
pregnancy. Hemolysis, Elevated Liver Enzymes and Low Platelets syndrome
(HELLP) was defined according to NICE guidelines12 and
renal impairment was defined as a serum creatinine above 120 umol/L.
Baseline data were obtained by interview and extraction from medical
records. All data were entered and stored using REDCap (Research
Electronic Data Capture) tools hosted at Stellenbosch
University.13, 14 Data were double checked for
accuracy and controlled with original data collection forms.