Introduction
High blood pressure in pregnancy can be categorised into 3 types:
Essential Hypertension
Essential hypertension is when the mother has pre-existing high blood pressure BEFORE she became pregnant. Often, the mother will already be on medication for the blood pressure through her GP, and sometimes this medication may need changing as it is not appropriate to take it during pregnancy.
Anyone with essential hypertension contemplating pregnancy should have a pre pregnancy check with their GP or obstetrician so medications can be reviewed and any pre pregnancy testing of the mother’s medical state relevant to a pregnancy can be performed.
Management involves close monitoring of blood pressure and the mother’s health with regular visits, occasional increases in medication to control blood pressure, and close surveillance of fetal growth and wellbeing, often with an extra growth ultrasound or two. An induction of labour around the 38-39 week mark may also be required. The presence of essential hypertension increases the risk of pre-eclampsia developing during the pregnancy (see below).
Pregnancy Induced Hypertension (PIH)
As the name implies, this is high blood pressure that during the pregnancy in a woman who has not had high blood pressure before. High blood pressure is generally considered to be blood pressure consistently over 140 / 90mmHg. It most often occurs late in the pregnancy, generally after 36 weeks or so.
Sometimes, earlier onset pregnancy induced hypertension may need medication to keep the blood pressure under control to maintain a healthy placenta and thus healthy baby. Close monitoring of the baby’s weight and placental function will be required during the pregnancy with extra formal scans. Sometimes, earlier delivery may be indicated if there are concerns about baby’s growth between scans, or evidence that the placental function is deteriorating.
If good control of blood pressure is achieved during the pregnancy, and ultrasound scans are reassuring with regards to fetal growth and the placental function, the pregnancy can safely be left until after 38 weeks to allow baby to mature as much as possible in the uterus. Often, an induction of labour will be required for PIH around the 38–40-week mark to prevent the onset of pre-eclampsia.
Pre-eclampsia
Pre-eclampsia is a very serious condition of pregnancy which is defined as high blood pressure and protein loss in the urine greater than that considered to be normal protein loss in pregnancy. This may be associated with blood test abnormalities involving the liver, kidneys, and general blood cell counts.
Untreated, pre-eclampsia can progress to eclampsia, which results in the mother developing seizures, which can result in brain damage for mother and baby, or even rarely death of both mother baby.
The only cure for pre-eclampsia is to deliver the baby and ultimately the placenta, which is thought to be the cause of pre-eclampsia. Pre-eclampsia varies in its severity, and certainly if the pregnancy is still at a premature stage, and the pre-eclampsia is not at a severe stage, then admission to hospital and intensive monitoring may be possible to try and gain some further maturity for the pregnancy before delivery of the baby becomes mandatory.
Should the gestation of the baby be particularly premature, transfer to a large centre like The Royal Brisbane and Women’s Hospital may be necessary, due to the need for a neonatal intensive care unit (NICU) for babies born under 32 weeks gestation.
The method of delivery of the baby in cases of pre-eclampsia will depend on the severity of the pre-eclampsia, gestation of the baby, and favourability of the mother for induction of labour.
Almost always, severe pre-eclampsia and premature delivery of the baby will require a Caesarean Section. Less severe pre-eclampsia conditions after 37 weeks will often allow for induction of labour to be considered.
In severe cases of pre-eclampsia though, regardless of the gestation, close monitoring of the mother will be required for at least 24 hours after the delivery as the risk of seizures is still present for this time. Often an infusion of a medicine called Magnesium will be required to protect the mother from seizures also.