Raised blood pressure during pregnancy is cause for concern.

Pre-eclampsia (PET) is a condition that only occurs in pregnancy, usually after the 20th week, and comprises a combination of raised blood pressure (hypertension), protein in the urine (proteinuria) and swelling (oedema) of the ankles, hands or face.

Ankle oedema is common in pregnancy and is usually of no significance, but, if severe, it can be a feature of PET. PET is mild in most instances but is always of concern to the doctor because complications can arise in the mother and foetus when it is severe. Sometimes, some persons might have PET superimposed on their hypertension.

The causes of PET are unknown. It is believed to be related to problems in the placental blood vessels. These factors increase the risk of PET: first pregnancy, above 40 years, previous history of PET, a body mass index of 35 or more, weight of 90kg or more, long interval between pregnancies (more than 10 years apart), multiple pregnancy (twins or triplets), medical conditions (like raised blood pressure, diabetes or kidney problems), and family members with PET.

PET affects both mother and baby. It affects placental development, leading to slower growth of the foetus. This is due to a decreased placental blood supply which leads to reduced oxygen and nutrient supply to the developing foetus. The amniotic fluid surrounding the foetus might decrease. If the placenta is severely affected, the foetus might be distressed in the uterus. It might also not be able to take the stress of labour.

Severe PET, if untreated, can lead to eclampsia in which there are one or more fits just like that of epilepsy. It is estimated that severe PET and eclampsia occurs in one in 200 and one in 2,000 pregnancies respectively. Fits are life threatening for both mother and baby.

Eclampsia may be associated with failure of kidney, liver or lung function. A combined failure of these organs, called the HELLP syndrome, is life threatening. In this condition, red blood cells break down, liver cells are damaged and there are clotting problems because of low levels of blood platelets.

Diagnosis

There are usually no symptoms in mild PET, which is usually detected at routine antenatal examination. A diagnosis of PET is made when at least two of its characteristics are present. Although the severity of PET is based mainly on blood pressure and proteinuria, other organs may be involved, with symptoms referable to them.

Severe PET usually develops late in pregnancy and/or soon after the baby is born. The symptoms include: headache, vision symptoms like blurred vision or flashes of light, sudden swelling of the limbs, excessive weight gain due to fluid retention, nausea and/or vomiting, abdominal pain, shortness of breath and confusion.

Mild PET is usually monitored with regular checking of the blood pressure and urine at the antenatal clinic. If the blood pressure is rising or there is severe PET, the patient is monitored in the hospital. The objective is to control the blood pressure and prevent fits from occurring. The blood pressure and urine are checked regularly. Blood tests may be carried out to check on clotting, kidney, and liver functions. Foetal growth and well-being are monitored with ultrasound and the foetal heart is checked regularly.

Medicines which are given by mouth or via a drip, to control the blood pressure and/or prevent fits, do not harm the baby.

Obstetricians are divided as to the treatment of women whose diastolic blood pressure is between 100mmHg and 110mmHg. Although medicines will decrease the risk of severe PET, it appears to lead to a small reduction in the baby’s birth weight. Methyldopa has been found safe in long-term follow-up of delivered babies whilst there are similar benefits reported for labetalol. The newer medicines like the angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor-blocking drugs (ARB) and diuretics are usually not used because of unacceptable foetal adverse effects in the first two classes of medicines and because it is contraindicated in the last class.

The only way to prevent the development of severe PET and/or eclampsia is to deliver the baby.

When there is severe PET with a risk of eclampsia, magnesium sulphate is usually prescribed. This medicine is used when a decision has been made to deliver the baby and for 24 hours after delivery or 24 hours after the last fit, whichever is the last. During magnesium sulphate therapy, there will be regular assessment of the respiratory rate, oxygen saturation, reflexes and urine output.

When there are eclamptic fits, attention is focused on the airway, breathing and circulation. Magnesium sulphate is the first line medicine for controlling the fits whether they are initial or recurrent. Once the situation is stabilised, arrangements will be made to deliver the baby.

As each pregnancy is unique. The timing and mode of delivery will depend on the patient’s particular circumstances. The obstetrician will discuss with the patient and her spouse the various options available, which is dependent on how severe the PET is and the foetal condition.

The obstetrician will try to achieve a delivery after 36 weeks of pregnancy. If the PET is not severe, there will be regular monitoring to check that it is safe to continue with the pregnancy until such time when labour starts spontaneously or is induced. During this period, medicines will be prescribed to keep the blood pressure under control.

Management challenge

If the symptoms worsen or the PET is affecting the patient and/or foetus, early delivery will be advised. If the foetus is premature, an injection of steroids may be given to help the foetal lungs mature so that breathing difficulties can be averted after the baby’s birth.

If the cervix is favourable, induction of labour will be carried out. An epidural is usually advised to provide pain relief and to control the blood pressure, which will usually be raised during the course of labour. If the cervix is unfavourable or there are other maternal or foetal considerations present, a Caesarean section will be carried out. There will be continued monitoring of the mother after the baby is born. This is because about half of women who develop eclampsia do so after the delivery.

If the blood pressure is still raised six weeks after the baby’s birth or there is still proteinuria, a referral will be made to a physician or nephrologist to check on the kidney function.

If there has been severe PET or eclampsia, it is advisable to consult your general practitioner or obstetrician prior to starting another pregnancy. About 20% of women may develop PET in a subsequent pregnancy. Some women may have residual organ damage due to the complications of the condition. An assessment of risk factors will be made and preventive treatment may be instituted.

PET poses a continuous management challenge for the obstetrician. While attempting to get the foetus to as near a mature state as possible, he or she has to also ensure that the mother’s blood pressure is controlled and prevent the PET from getting severe, when the risk of eclamptic fits increases. The obstetrician’s efforts are influenced by the fact that the only way to stop the progress of the PET is to deliver the baby.

Source: Dr Milton Lum