Pre-eclampsia rarely happens before the 20th week of pregnancy. Most cases occur after 24-26 weeks and usually towards the end of pregnancy.
Although less common, the condition can also develop for the first time during the first six weeks after the birth.
Most people only experience mild symptoms, but it's important to manage the condition, in case severe symptoms or complications develop. Generally, the earlier pre-eclampsia, develops the more severe the condition will be.
Early signs and symptoms
Initially, pre-eclampsia causes:
You probably won't notice any symptoms of either of these, 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 doesn't suggest pre-eclampsia. However, if protein in the urine is found at the same time as high blood pressure, it's a good indicator of the condition.
Read more about diagnosing pre-eclampsia.
As pre-eclampsia progresses, it may cause:
- severe headaches
- vision problems, such as blurring or seeing flashing lights
- severe heartburn
- pain just below the ribs
- nausea or vomiting
- excessive weight gain caused by fluid retention
- feeling very unwell
- sudden increase in oedema – swelling of the feet, ankles, face and hands
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 when the midwife or doctor measures you.