Extracted from Survival Guide to Midwifery, 2nd Edition (2012) Diane M. Fraser and Margaret A. Cooper, Oxford; Churchill Livingstone: 2012. Courtesy Elsevier

Blood pressure (BP) is taken to ascertain normality and provide a baseline reading for comparison throughout pregnancy.

• Systolic BP may be falsely elevated if the woman is nervous or anxious; a full bladder can cause an increase in BP
• The woman should be seated or resting in a lateral position on the couch when BP is taken
• A systolic BP of 140mmHg or diastolic pressure of 90mmHg at booking is indicative of hypertension and will need careful monitoring throughout pregnancy

Sphygmomanometers should be calibrated for use in pregnancy and regularly maintained. The correct size cuff for the woman should be used - BP can be overestimated as a result of using a cuff of inadequate size relative to the arm circumference. Two cuffs should be available with inflation bladders of 35cm for normal use and 42cm for large arms. BP should be recorded as accurately as possible to the nearest 2mmHg. BP over 140/90mmHg when accompanied by proteinuria (>1+ on dipstick, or >0.3g/L in a clean catch specimen) is suspicious for pre-eclampsia. BP over 140/90mmHg in the absence of proteinuria but accompanied by headache, blurred vision, abdominal/epigastric pain or altered biochemistry may also indicate pre-eclampsia.

Hypertension

May be chronic and pre-existing prior to pregnancy or gestational, developing during pregnancy with or without other signs of pre-eclampsia.