• Dr Peter Chew

Aspirin and Pre-eclampsia (Pregnancy Hypertension)

D, a 37 year-old nurse, was surprised and puzzled when I prescribed aspirin for her present pregnancy. She was at 13 weeks of gestation. “Doc,” she asked, “isn’t aspirin used for headache and for patients recovering from a stroke or heart attack? Why is it given during pregnancy?” In her first pregnancy 2 years ago, she had severe pre-eclampsia at the last trimester of pregnancy. An emergency Caesarean section was performed at 34 weeks gestation to prevent serious life-threatening complications to the mother and the foetus. Fortunately, her baby weighing 1.2 kg survived albeit staying in the neonatal intensive care unit for a while. I explained to her that low-dose aspirin was given for two reasons. It relaxes the uterine blood vessels and keeps the flow of nutrients and oxygen to the baby. It also delays and prevents the onset of pre-eclampsia.


What is Pre-eclampsia? Pre-eclampsia is a pregnancy complication characterized by high blood pressure, protein in the urine and swelling in the legs, face and hands. It affects about 10 per cent of first pregnancies and the symptoms and signs usually begin after 20 weeks of pregnancy. Left untreated, pre-eclampsia can lead to serious and even fatal maternal consequences such as stroke, seizure, as well as kidney, liver and heart failure. The baby may die from premature birth, early separation from the placenta and asphyxia. The growth of the baby is also affected from malfunction of the placenta. The cause of pre-eclampsia is still unknown. Medical conditions such as hypertension, kidney disease and diabetes are associated with a higher risk of developing pre-eclampsia. How does aspirin help in pre-eclampsia? Research studies have suggested that low-dose aspirin helps prevent or delay the onset of pre-eclampsia in 2 ways: 1. It inhibits thromboxane, a hormone that raises blood pressure and is elevated in women with pre-eclampsia. 2. Aspirin also improves blood flow across the placenta, by dilating the uterine arteries. Inadequate placental blood supply plays a key role in initiating pre-eclampsia. According to a comprehensive review of the scientific evidence by the USPSTF(U.S. Preventive Services Task Force) in 2014, prenatal aspirin has been shown to reduce the risk of pre-eclampsia by 24%. Risks of taking low-dose aspirin in pregnancy Maternal Risks: Scientific studies have shown that consumption of low-dose aspirin during pregnancy does not increase the risk of bleeding complications such as early placental separation and postpartum hemorrhage.


Fetal Risks: Several systematic reviews have shown intake of aspirin does not increase the risk of congenital anomalies. There have been no adverse fetal or neonatal outcomes. Recommended use of prenatal use of low-dose aspirin According to the USPSTF guidelines for the prevention of preeclampsia which is supported by the American College of Obstetricians and Gynecologists, low-dose aspirin (81 mg/day) as prophylaxis is recommended in women at high risk of preeclampsia and should be initiated between 12 weeks and 28 weeks of gestation (optimally before 16 weeks) and continued daily until delivery.

The criteria for high-risk patients include:

  • History of severe pre-eclampsia

  • Multiple pregnancy

  • Chronic hypertension

  • Type 1 and 2 Diabetes

  • Kidney disease

  • Autoimmune diseases e.g. SLE

D understood the benefits of taking low-dose aspirin to reduce the risk of pre-eclampsia, premature birth and intrauterine growth restriction in her present pregnancy. She took the medication with good compliance. Her antenatal course remained uneventful with normal blood pressure. She opted for a repeat cesarean section at 38 weeks gestation and delivered a healthy normal baby boy weighing 3 Kg.

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