Pre-eclampsia rarely happens before the 20th week of pregnancy. Most cases occur in the third trimester, after 24-26 weeks.
Although less common, the condition can also develop for the first time during the first six weeks after the birth.
Generally, the earlier pre-eclampsia develops the more severe the condition will be.
Initially, pre-eclampsia causes:
You probably won't notice these symptoms, but your GP or midwife should pick them up during your routine antenatal appointments.
High blood pressure affects 10-15% of all pregnant women, so this alone does not suggest pre-eclampsia. However, if protein in the urine is found at the same time as high blood pressure, it is a good indicator of the condition.
Read more about diagnosing pre-eclampsia.
As pre-eclampsia develops, it can cause fluid retention (oedema), which often leads to the sudden swelling of the feet, ankles, face and hands.
Oedema is another common symptom of pregnancy, but it tends to be in the lower parts of the body, such as the feet and ankles. It will gradually build up during the day. If the swelling is sudden and it particularly affects the face and hands, it could be pre-eclampsia.
As pre-eclampsia progresses, it may cause:
- severe headaches
- vision problems, such as blurring or seeing flashing lights
- pain just below the ribs
- excessive weight gain caused by fluid retention
- feeling very unwell
If you notice any symptoms of pre-eclampsia, seek medical advice immediately by calling your GP surgery or NHS 111.
Without immediate treatment, pre-eclampsia may lead to a number of serious complications, including:
- convulsions (eclampsia)
- HELLP syndrome, a combined liver and blood clotting disorder
However, these complications are rare. Read more about the complications of pre-eclampsia.
Signs in the unborn baby
The main sign of pre-eclampsia in the unborn baby is slow growth. This is caused by poor blood supply through the placenta to the baby.
The growing baby receives less oxygen and fewer nutrients than it should, which can affect development. This is called intra-uterine or foetal growth restriction.
If your baby is growing more slowly than usual, this will normally be picked up during your antenatal appointments.