USE OF ASPIRIN IN PREGNANCY

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(Date of issue: July 2014, Version: 2)

This is a UKTIS monograph for use by health care professionals. For case-specific advice please contact UKTIS on 0344 892 0909. To report an exposure please download and complete a pregnancy reporting form. Please encourage all women to complete an online reporting form.

A corresponding patient information leaflet on aspirin use in pregnancy is available at www.medicinesinpregnancy.org.

Summary

Low-dose aspirin (75-300mg/day) is used as an antiplatelet medication in the prophylaxis of thromboembolic cerebrovascular disease, myocardial infarction and pre-eclampsia. Higher doses of aspirin (up to 4g/day) are used in the control of mild to moderate pain and pyrexia. 

There is a large body of evidence that shows no association between the use of low-dose aspirin (LDA) during pregnancy and increased risk of spontaneous abortion or stillbirth. Fewer data are available regarding aspirin use at analgesic doses, but again no association with these two outcomes has been reported. 

Various malformations have been reported following therapeutic maternal use of aspirin during pregnancy, however with the exception of a possible increased incidence of gastroschisis, no specific pattern of malformations has been observed and a causal association with aspirin has not been proven.

There is no evidence of an increased incidence of low birth weight, intrauterine growth retardation or prematurity following low dose aspirin exposure in utero. A meta-analysis of the available data suggested that initiation of treatment with low dose aspirin before 16 weeks gestation in women at risk of pre-eclampsia and other placenta-mediated adverse pregnancy outcomes may have a protective effect on the incidence of fetal growth restriction, preterm delivery and perinatal death. No studies which investigated the incidence of low birth weight, intrauterine growth retardation or prematurity following maternal aspirin use at analgesic doses were found.

Chronic exposure to analgesic doses of aspirin >300mg/day from 30 weeks of pregnancy may be associated with neonatal bleeding complications (particularly in premature infants) and premature closure of the ductus arteriosus (DA), resulting in pulmonary vasculature abnormalities and persistent pulmonary hypertension of the newborn (PPHN). These effects have not been reported with low dose aspirin use.

Carcinogenicity in the offspring in relation to in utero aspirin exposure has not been extensively studied. Children exposed to analgesic doses of aspirin in utero were no more likely to develop leukaemia at one year of age than those not exposed. No studies investigating carcinogenicity following use of low dose aspirin in pregnancy were located. 

Two studies suggest no increased risk of impaired neurodevelopment after in utero LDA exposure. Two other studies which yielded conflicting results regarding IQ following in utero exposure did not report on maternal dose.

Regular use of analgesic doses of aspirin in the third trimester should be avoided if possible. In circumstances where the maternal clinical condition requires treatment with analgesic doses of aspirin during the third trimester, discussion with an obstetrician regarding fetal monitoring for oligohydramnios and DA patency is recommended. The neonate should also be monitored for bleeding complications, particularly if preterm. Exposure to therapeutic doses of aspirin prior to the third trimester would not be considered an indication for any additional fetal monitoring. 

NOTE: This monograph refers only to use of aspirin in therapeutic dosage (up to 4g/day). For exposure to aspirin in excess of 4g/day please refer to the aspirin overdose in pregnancy monograph.

This document is regularly reviewed and updated. Only use UKTIS monographs downloaded directly from TOXBASE.org or UKTIS.org to be sure you are using the most up-to-date version.

This is a summary of the full UKTIS monograph for health care professionals and should not be used in isolation. The full UKTIS monograph and access to any hyperlinked related documents is available to health care professionals at www.toxbase.org.

If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.

If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.

Disclaimer: Every effort has been made to ensure that this monograph was accurate and up-to-date at the time of writing, however it cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes of the measures recommended. The final decision regarding which treatment is used for an individual patient remains the clinical responsibility of the prescriber. This material may be freely reproduced for education and not for profit purposes within the UK National Health Service, however no linking to this website or reproduction by or for commercial organisations is permitted without the express written permission of this service. This document is regularly reviewed and updated. Only use UKTIS monographs downloaded directly from TOXBASE.org or UKTIS.org to ensure you are using the most up-to-date version.