Use the fifth Korotkoff sound

The measurement of diastolic blood pressure during pregnancy offers plenty of scope for error. Most people still use a mercury sphygmomanometer, with all the pitfalls that are familiar outside obstetrics–“white coat” hypertension, digit preference, cuff size, differences between arms, and poorly calibrated equipment. To these should be added the influence of posture and gestation in a pregnant woman, so any advance in getting it right is to be welcomed. There is now good evidence to support using the fifth Korotkoff sound when measuring diastolic blood pressure in pregnancy.

Although measuring blood pressure and detecting hypertension remain at the core of antenatal monitoring, there has long been uncertainty about whether to record diastolic pressure as the point when the sounds muffle (Korotkoff phase IV) or when they disappear (phase V). The World Health Organisation recommends the use of phase IV,1 …