Hypertensive disorders complicate around 10 % of pregnancies and are a major cause of maternal and perinatal morbidity [1]. Blood pressure measurement is therefore an important component of routine antenatal screening and is carried out at every antenatal visit during pregnancy [2]. Self-monitoring of blood pressure at home is becoming more popular and makes frequent measurements possible at home in a well-known environment [3]. The recent COVID-19 pandemic underlined the advantages of home blood pressure monitoring (HBPM) in pregnancy enabling women to continue with frequent blood pressure monitoring and reduce the number of face-to-face appointments with the health services [4].

There has been debate regarding whether clinic and home blood pressure measurements in pregnancy are equivalent [5]. The International Society for the Study of Hypertension in Pregnancy (ISSHP) consider home blood pressure readings to be 5 mmHg lower than clinical readings and recommend a threshold for hypertension at ≥135/85 mmHg for home readings based on expert opinion [6]. However, the evidence base on HBPM during pregnancy to guide such recommendations is sparse. Only a limited number of small studies have compared blood pressure readings obtained at home with those from the clinic with conflicting results [5], [7]. A recent systematic review and meta-analysis including 15 studies reported blood pressures to be lower at home than in the clinic with a difference of 4/3 mmHg for systolic (sBP) and diastolic blood pressure (dBP), respectively [7]. However, substantial heterogeneity and potential publication bias was present, with variation in results by hypertensive status and the authors concluded that the literature regarding the equivalency of clinic and home blood pressure was not definitive, with more research needed. It therefore remains uncertain whether there is a general difference between the two modalities for blood pressure measurement in pregnancy.

The aim of this study was to compare clinic and home blood pressure readings in normotensive women at higher risk of pregnancy hypertension in the antenatal period from gestational week 20+0 until 40+0 in order to evaluate differences between the two modalities.