What are the effects of Acetylsalicylic acid (Aspirin) on pregnancy?

From the Guidelines

Aspirin should be used with caution during pregnancy, and low-dose aspirin (81mg daily) may be recommended for certain high-risk pregnant women to prevent preeclampsia, typically starting between 12-16 weeks of pregnancy and continuing until delivery, as supported by the US Preventive Services Task Force recommendation statement 1. When considering the use of aspirin during pregnancy, it is essential to weigh the potential benefits against the potential harms. The evidence suggests that low-dose aspirin use seems to have no short-term harms during pregnancy, with no statistically significant increase in placental abruption, perinatal mortality, or postpartum hemorrhage 1. Some key points to consider include:

• Low-dose aspirin may be beneficial for women at increased risk for preeclampsia, with a pooled relative risk of 0.81 [CI, 0.65 to 1.01] for perinatal mortality 1.
• There is limited evidence on long-term outcomes in offspring from in utero exposure to low-dose aspirin, but one observational study found no difference in the rate of cryptorchidism between male infants exposed to aspirin and those who were not 1.
• Regular-strength aspirin (325mg) should be avoided, especially in the third trimester, due to the potential for complications such as premature closure of the fetal ductus arteriosus, delayed labor, increased bleeding during delivery, and pregnancy loss.
• Acetaminophen (Tylenol) is typically the safer first-line option for pain relief or fever during pregnancy. It is crucial for pregnant women to consult their healthcare provider before taking aspirin or any other medication, as the risks and benefits must be individually assessed based on their specific medical situation 1.

From the FDA Drug Label

If pregnant or breast-feeding ask a health professional before use. it is especially important to use aspirin during the last 3 months of pregnancy unless definitely directed to do so by a doctor because it my cause problems in the unborn child or complications during delivery. Aspirin use during pregnancy, especially in the last 3 months, is not recommended unless directed by a doctor due to potential problems in the unborn child or complications during delivery 2.

• Key consideration: Consult a health professional before using aspirin during pregnancy or breast-feeding.
• Main precaution: Avoid using aspirin in the last 3 months of pregnancy unless medically necessary.

From the Research

Aspirin Use During Pregnancy

• Aspirin has been used during pregnancy to prevent or delay the onset of preeclampsia, with low-dose aspirin considered safe and associated with a low likelihood of serious maternal or fetal complications 3.
• The American College of Obstetricians and Gynecologists recommends daily low-dose aspirin beginning in the late first trimester for women with a history of early-onset preeclampsia and preterm delivery at less than 34 0/7 weeks of gestation, or for women with more than one prior pregnancy complicated by preeclampsia 3.
• Low-dose aspirin (81 mg/day) 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 3.

Indications for Aspirin Use

• Women at risk of preeclampsia are defined based on the presence of one or more high-risk factors (history of preeclampsia, multifetal gestation, renal disease, autoimmune disease, type 1 or type 2 diabetes, and chronic hypertension) or more than one of several moderate-risk factors (first pregnancy, maternal age of 35 years or older, a body mass index greater than 30, family history of preeclampsia, sociodemographic characteristics, and personal history factors) 3.
• Aspirin has been proven efficient to prevent pre-eclampsia and fetal growth restriction in high-risk patients 4.
• The benefits of prescribing aspirin have been demonstrated neither for vascular placental disease prevention in low risk patients, nor in cases of unexplained recurrent miscarriages 4.

Optimal Dosage of Aspirin

• A dosage of 80-100 mg/day is recommended for preventing preeclampsia in high-risk pregnant women, although individual circumstances should be considered for optimizing the balance between effectiveness and safety 5.
• Different doses of aspirin showed a reduction in preeclampsia incidence, but there was no significant difference in efficacy between the dosage groups 5.
• Side effects did not significantly differ between placebo and different aspirin dosage groups 5.

Clinical Practice Guidelines

• There is general agreement in the reported indications for aspirin intake in pregnancy, with prior preeclampsia and maternal medical co-morbidity associated with increased risk of preeclampsia being the major indications for aspirin intake 6.
• There was heterogeneity in the recommendations provided by the different clinical practice guidelines as regards the gestational age at which aspirin should be commenced 6.
• The quality of clinical practice guidelines on aspirin use in pregnancy was assessed using the "The Appraisal of Guidelines for REsearch and Evaluation (AGREE II)" tool 6.