Indications for Aspirin Prophylaxis

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CCRMC OBGYN Prenatal Guideline
Consultation available 24 hours per day from OB on-call at 925-370-5608 or via page/amion, via inbasket to OB dept member or by calling Perinatologist at 510-444-0790 during the day and 510-204-1572 after hours.
Consultation appointments or transfer of care to more experienced prenatal clinician available at major clinics sites—see consultation guidelines for more information.

Criteria for Aspirin Prophylaxis in Pregnancy


In large met analysis aspirin prophylaxis from 12-16 weeks in pregnancies at high risk for preeclampsia, risk of preeclampsia decreased by 24%, preterm birth due to preeclampsia by 14%, IUGR by 20%. We recommend using 81mg daily although one study suggests the best dose might be 150mg daily. Some experts recommend 162mg (two tabs) daily. The risk of low dose ASA in pregnant is thought to be negligible and there is no demonstrated increased risk of abruption, postpartum hemorrhage, fetal harm, intracranial bleeding, congenital anomalies.
We recommend using the USPSTF Guidelines to determine candidates for aspirin prophylaxis to prevent preeclampsia.
https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/low-dose-aspirin-use-for-the-prevention-of-morbidity-and-mortality-from-preeclampsia-preventive-medication

Criteria is one of the following major risk factors for preeclampsia.
  • History of preeclampsia, especially when accompanied by and adverse outcome
  • Multifetal gestation
  • Chronic Hypertension --> BP > 140/90 or taking antihypertensive medication
  • Diabetes Type 1 or Type 2
  • Renal Disease
  • Autoimmune disease (SLE, antiphospholipid syndrome)

or several of these moderate risk factors:
  1. Nulliparity or
  2. > 10 years since last birth
  3. Age > 35
  4. H/o preeclampsia in mother or sister
  5. Age ≥35 yearsAfrican
  6. American race
  7. Low socioeconomic level
  8. Previous small for gestational age infant *
  9. Previous stillbirth *

At CCRMC/UBCP Maternal-Fetal Medicine also recommend ASA prophylaxis for:
  • Prior documented or convincing history of SGA baby
  • Prior unexplained fetal demise in the second or third trimester

Timing of Prophylaxis

  • Benefit shown if started between 12-16 weeks gestation. Unclear benefit if started later than 16 weeks EGA. ACOG suggests starting up to 28 weeks gestation if not started earlier as recommended.
  • OK to start earlier in first trimester no concern for ectopic
  • We suggest stopping ASA at 37 weeks, or one week before delivery if planned prior to 37 weeks EGA. It is considered safe to continue until delivery.