Daily Low-Dose Aspirin Recommended to Prevent Preeclampsia, Preterm Birth

September 12, 2014
Michael R. Page, PharmD, RPh

Roughly 1 in every 3 obstetric complications are related to preeclampsia.

Roughly 1 in every 3 obstetric complications are related to preeclampsia.

Worldwide, 2% to 8% of all pregnant women develop preeclampsia, resulting in harm to both the mother and fetus.

Of the obstetric complications that occur in the United States each year, approximately 1 in 3 are related to preeclampsia. Additionally, preeclampsia and eclampsia cause approximately 12% of all maternal deaths in the country.1

To improve these statistics, new preventive recommendations from the United States Preventive Services Task Force (USPSTF) advise women at high risk for developing preeclampsia to take an 81-mg tablet of aspirin daily, starting at 12 to 28 weeks of gestation.1

Risk Factors and Signs

Factors that place women at high risk for preeclampsia include1:

  • Past cases of preeclampsia
  • Simultaneous fetal gestation
  • Chronic hypertension
  • Type 1 or type 2 diabetes mellitus
  • Having renal disease, and
  • Having any autoimmune disease

Each of these factors increases a pregnant woman’s risk of developing preeclampsia to approximately 8%.1

Laboratory abnormalities associated with preeclampsia include high blood pressure (140/90 mm Hg), and, in women who are beyond 20 weeks' gestation, high protein levels in urine (0.3 grams or more excreted in urine within 24 hours). Other abnormalities associated with preeclampsia include thrombocytopenia, impaired liver function, renal insufficiency, pulmonary edema, and cerebral or visual disturbances.1

Magnitude of Benefit and Evidence Base

Among women at high risk for developing preeclampsia, a daily dose of 60 to 150 mg of aspirin reduces the likelihood of developing preeclampsia by approximately 24%, preterm birth caused by preeclampsia by 14%, and intrauterine growth restriction by 20%.1,2

The change to recommendations occurred primarily as a result of a systematic evidence review and meta-analysis published in the May 2014 edition of the Annals of Internal Medicine. Of the qualifying studies obtained, the researchers included 2 large studies, 13 smaller studies, 6 randomized controlled trials, and 2 observational studies in their analysis.2-7

Based on an absolute risk reduction between 2% and 5%, the researchers estimated that, in order to prevent 1 additional case of preeclampsia, between 20 and 50 additional patients at high risk for the pregnancy complication would need to take a low-dose aspirin daily. Similarly, preventing 1 case of intrauterine growth restriction would require treating 20 to 100 additional patients with aspirin, while preventing 1 additional case of preterm birth would require treating 25 to 50 additional patients.2

Risks of Treatment

Use of aspirin in pregnant women was not associated with any adverse outcomes in those at high risk for preeclampsia. Importantly, however, the studies included in the metaanalysis did not evaluate long-term outcomes. Therefore, future studies may be required to fully elucidate the risks of aspirin use during pregnancy. As with any recommendation, it is important to take into account each patient’s clinical condition, risk factors, and medical history.2

References:

1. Lefevre M; for the US Preventive Services Task Force. Low-dose aspirin use for the prevention of morbidity and mortality from Preeclampsia: US Preventive Services Task Force recommendation statement [published online September 9, 2014]. Ann Intern Med. 2014.

2. Henderson JT, Whitlock EP, O'Connor E, Senger CA, Thompson JH, Rowland MG. Low-dose aspirin for prevention of morbidity and mortality from preeclampsia: a systematic evidence review for the US Preventive Services Task Force. Ann Intern Med. 2014;160(10):695-703.

3. Sibai BM, Caritis SN, Thom E, et al. Prevention of preeclampsia with low-dose aspirin in healthy, nulliparous pregnant women. The National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units. N Engl J Med. 1993;329(17):1213-1218.

4. Caritis S, Sibai B, Hauth J, et al. Low-dose aspirin to prevent preeclampsia in women at high risk. National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units. N Engl J Med. 1998;338(11):701-705.

5. Duley L, Henderson-Smart DJ, Meher S, King JF. Antiplatelet agents for preventing pre-eclampsia and its complications. Cochrane Database Syst Rev. 2007.

6. Askie LM, Duley L, Henderson-Smart DJ, Stewart LA; PARIS Collaborative Group. Antiplatelet agents for prevention of pre-eclampsia: a meta-analysis of individual patient data. Lancet. 2007;369(9575):1791-1798.

7. CLASP collaborative group. Low dose aspirin in pregnancy and early childhood development: follow up of the collaborative low dose aspirin study in pregnancy. CLASP collaborative group. Br J Obstet Gynaecol. 1995;102(11):861-868.