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Preclampsia screening

What is pre-eclampsia?

Pre-eclampsia (PE) is a serious complication of pregnancy that can affect both pregnant women and their unborn baby (or babies).  It is the most common medical condition in pregnancy, affecting around 5 percent of all pregnancies. It is characterised by high blood pressure, swelling along with rapid weight gain due to fluid retention, and protein in the urine. It can range from mild to severe and can affect various systems of the body. PE frequently coexists with poor placental function (placental insufficiency). It can therefore restrict your baby's growth. It can also cause premature separation of the placenta (placental abruption). Aside from major pregnancy complications such as fetal death in utero and maternal stroke, it is the leading cause of medically indicated preterm birth when it is diagnosed in pregnancy.

 

Are some women more likely to develop pre-eclampsia?

The exact cause of pre-eclampsia is not known but there are recognised risk factors. You're more likely to get pre-eclampsia in a first pregnancy or if you had it in a previous pregnancy. You are also more at risk if you are older, overweight, have a chronic medical problem that affects your blood system, including high blood pressure, lupus, kidney problems, or diabetes, or if your mum had pre-eclampsia. Smoking and multiple pregnancy also increases your risk. 

 

Can my risk of preeclampsia be assessed?

Your risk of developing pre-eclampsia later in pregnancy can be assessed in the first trimester of pregnancy.

Your obstetrician will refer you for a blood test at 10 weeks to test for pregnancy associated plasma protein A (PAPP-A) and placental growth factor (PlGF).

You then need an ultrasound between 11 and 14 weeks. You will be asked to fill out a form with your personal history. Your blood pressure will be taken and the blood flow in the uterine arteries will be measured with ultrasound. At the same time the early anatomy of your baby will be assessed for structural abnormalities.  

Recent advances in medicine have shown that by combining 4 parameters in the first trimester of pregnancy comprising:

  • Maternal demographic characteristics obtained by taking her clinical history;
  • Serum biochemical markers of pregnancy associated plasma protein A (PAPP-A) and placental growth factor (PlGF);
  • Maternal mean arterial blood pressure performed between 11 weeks 2 days and 13 weeks 6 days
  • Ultrasound of the maternal uterine arteries performed between 11 weeks 2 days and 13 weeks 6 days,

It is possible to reliably detect up to

  • 89% of the most severe form of PE or early onset PE, which is defined as onset before 34 weeks gestation;
  • 75% of moderate PE or preterm PE, defined as onset between 34 and 37 weeks; and
  • 47% of mild PE or term PE, defined as onset after 37 weeks

This level of detection is achievable with a false positive rate of 10%.  In other words, 10% of all pregnant women undergoing PE screening using the above method will be given a high risk result without eventually developing the condition.

At our practices we use the Fetal Medicine Foundation algorithm to calculate the risk for preeclampsia based on the 4 parameters mentioned above. The risk of developing pre-eclampsia before 34 weeks, before 37 weeks and before 42 weeks will be calculated and reported back to your obstetrician. There is no extra charge for this assessment. The cost is the same as a normal 12-14 week ultrasound. You will however be charged separately by the laboratory for the 10 week blood test your doctor organised. 

Pre-eclampsia prevention

The aim of preventative care is to delay or prevent the onset of pre-eclampsia in order for the pregnancy to be prolonged, allowing the fetus to grow and mature safely. There is no certain method of preventing pre-eclampsia but there is evidence to suggest that a single daily low-dose of aspirin commenced before 16 weeks gestation may help prevent the disease.