Enoxaparin
MedicationLow-molecular-weight heparin anticoagulant
Research strength: 3 / 5
Lepercq et al.'s 2001 cohort included 624 pregnancies; among 693 live births, it reported 17 major birth defects (2.5%) with no separate first-trimester estimate, and its authors did not attribute fetal or newborn events to enoxaparin. The FDA label describes the 2.5% rate as similar to background, notes that adequate controlled pregnancy studies are lacking, and calls for bleeding monitoring; it also warns of valve thrombosis in pregnant patients with mechanical heart valves. The FDA boxed warning states: "Epidural or spinal hematomas may occur in patients who are anticoagulated with low molecular weight heparins (LMWH) or heparinoids and are receiving neuraxial anesthesia or undergoing spinal puncture. These hematomas may result in long-term or permanent paralysis." FDA labeling delays catheter placement or removal at least 12 hours after lower doses and 24 hours after higher doses; the accessible September 16, 2025 ASRA version recommends 12 and 24 hours before neuraxial needle placement, and ACOG's public bulletin page does not show its detailed timing intervals. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- DailyMed: enoxaparin sodium injection labelDrug company label
- Lepercq et al., BJOG 2001, retrospective pregnancy cohortUS government
- Rowan et al., American Journal of Obstetrics and Gynecology 2001US government
- ACOG Practice Bulletin No. 196: Thromboembolism in PregnancyProfessional society
- ASRA fifth-edition regional anesthesia guideline
Research strength: 3 / 5
Lepercq et al.'s 2001 cohort included 624 pregnancies; among 693 live births, it reported 17 major birth defects (2.5%) with no separate second-trimester estimate, and its authors did not attribute fetal or newborn events to enoxaparin. The FDA label describes the 2.5% rate as similar to background, notes that adequate controlled pregnancy studies are lacking, and calls for bleeding monitoring; it also warns of valve thrombosis in pregnant patients with mechanical heart valves. The FDA boxed warning states: "Epidural or spinal hematomas may occur in patients who are anticoagulated with low molecular weight heparins (LMWH) or heparinoids and are receiving neuraxial anesthesia or undergoing spinal puncture. These hematomas may result in long-term or permanent paralysis." FDA labeling delays catheter placement or removal at least 12 hours after lower doses and 24 hours after higher doses; the accessible September 16, 2025 ASRA version recommends 12 and 24 hours before neuraxial needle placement, and ACOG's public bulletin page does not show its detailed timing intervals. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
Research strength: 3 / 5
The FDA label gives no separate third-trimester estimate, says adequate controlled pregnancy studies are lacking and calls for bleeding monitoring; it says a shorter-acting anticoagulant should be considered as delivery approaches and warns of valve thrombosis in pregnant patients with mechanical heart valves. ASH suggests scheduled delivery after stopping therapeutic-dose LMWH for VTE, but not scheduled delivery that interrupts prophylactic-dose LMWH. The FDA boxed warning states: "Epidural or spinal hematomas may occur in patients who are anticoagulated with low molecular weight heparins (LMWH) or heparinoids and are receiving neuraxial anesthesia or undergoing spinal puncture. These hematomas may result in long-term or permanent paralysis." FDA labeling delays catheter placement or removal at least 12 hours after lower doses and 24 hours after higher doses; the accessible September 16, 2025 ASRA version recommends 12 and 24 hours before neuraxial needle placement, and ACOG's public bulletin page does not show its detailed timing intervals. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- DailyMed: enoxaparin sodium injection labelDrug company label
- ASH 2018 pregnancy VTE guidelineUS government
- ACOG Practice Bulletin No. 196: Thromboembolism in PregnancyProfessional society
- ASRA fifth-edition regional anesthesia guideline
Enoxaparin — Breastfeeding
Research strength: 3 / 5
LactMed reports that a study of 12 fully breastfed term newborns found no detectable anti-Xa activity and no bleeding during maternal enoxaparin use. LactMed says enoxaparin is not expected to enter milk or be absorbed, and that no special precautions are required; the FDA label says human milk transfer and effects on the breastfed child are unknown. NHS SPS expects negligible milk transfer but advises monitoring infants for rare bruising or unusual bleeding, and limits its guidance to healthy, full-term infants. ASH lists LMWH among options for people who need anticoagulation while breastfeeding. Ask your provider about your situation.
Last reviewed: 2026-10-16
Pregnancy
Lepercq et al. (2001) retrospectively reviewed case notes from 55 French perinatal centers between 1988 and 1997: 624 pregnancies in 604 women, with enoxaparin used for acute treatment in 49 cases and thromboprophylaxis in 574. Among 693 live births, 17 major congenital abnormalities (2.5%) and 10 serious neonatal hemorrhages (1.4%) were reported; the authors judged none of the fetal or neonatal adverse events related to enoxaparin. The study was retrospective and was not a controlled comparison of enoxaparin with no treatment. The FDA label summarizes this cohort but lists 14 neonatal hemorrhages, while the primary abstract lists 10 serious neonatal hemorrhages; the differing descriptions may reflect different definitions, so the counts are not combined. A separate prospective audit by Rowan et al. (2001) followed 14 pregnancies in 11 women with mechanical heart valves receiving therapeutic enoxaparin plus aspirin. One participant with a documented valve thrombosis before treatment had a recurrence during treatment; the authors said efficacy in preventing valve thrombosis remained uncertain. The FDA label warns that enoxaparin used for thromboprophylaxis in pregnant patients with mechanical prosthetic valves may result in valve thrombosis.
Breastfeeding
LactMed (last revised 2025-11-15) reports no published maternal milk levels or infant drug levels. It summarizes a 1996 study of 12 fully breastfed term neonates whose mothers received 20 or 40 mg of enoxaparin daily: infant anti-Xa activity was undetectable at 5 to 7 days after birth, and no infant bleeding was observed. The infant anti-Xa study did not measure enoxaparin concentration in breast milk. LactMed infers that transfer and absorption are unlikely based on the molecule's large size and lack of oral bioavailability. NHS SPS (published 2024-01-19) says negligible milk transfer is expected, infant effects have not been reported, and recommends monitoring for unusual bruising or bleeding; its recommendations apply to healthy, full-term infants. ASH recommends LMWH as an option for breastfeeding people who need anticoagulation. The product label says it is unknown whether enoxaparin enters human milk and gives no information on effects in breastfed children or milk production.
Enoxaparin sodium is an injectable low-molecular-weight heparin anticoagulant. The cited DailyMed label describes its action through antithrombin and states that its multiple-dose vial contains benzyl alcohol as a preservative. That excipient detail is specific to the cited label's vial and should not be generalized to every enoxaparin product.
What was tested
The 2001 Lepercq study reviewed records across 55 French perinatal centers and included varying enoxaparin doses, treatment lengths, and indications; it reported pregnancy, maternal, fetal, and neonatal outcomes but no trimester-specific estimates. The 2001 Rowan prospective audit studied therapeutic enoxaparin plus aspirin in 14 pregnancies among 11 women with mechanical heart valves, with monthly predose and 4-hour postdose anti-Xa measurements. The LactMed breastfeeding evidence includes one small study of 12 term infants with anti-Xa activity measured after at least 5 days of breastfeeding; no published human milk concentrations were found.
How to describe breastfeeding evidence and infant monitoring
- Source A says
- The DailyMed label says it is unknown whether enoxaparin enters human milk and that there is no information about effects on breastfed children or milk production. LactMed says no special precautions are required. (DailyMed: enoxaparin sodium injection label, LactMed: Enoxaparin)
- Source B says
- NHS SPS expects negligible milk transfer and says infant effects have not been reported, but advises monitoring for rare bruising or unusual bleeding. ASH lists LMWH as an option for breastfeeding people who need anticoagulation. (NHS SPS: Using heparins during breastfeeding, ASH 2018 pregnancy VTE guideline)
- Why they differ
- The label reports that human milk transfer and infant effects are unknown. LactMed and NHS SPS use the large molecule size, expected low absorption, and a very small infant study to describe likely exposure; NHS SPS adds precautionary monitoring.
- What the evidence shows overall
- The evidence supports a compatible rating for breastfeeding, but the direct infant evidence is limited to a small series and case reports. NHS SPS limits its guidance to healthy, full-term infants and advises monitoring, while LactMed says no special precautions are required.
- The FDA label says pregnant patients receiving enoxaparin should be monitored for bleeding or excessive anticoagulation and that use of a shorter-acting anticoagulant should be considered as delivery approaches. (DailyMed: enoxaparin sodium injection label)
- ASH suggests scheduled delivery with prior discontinuation for therapeutic-dose LMWH used to treat VTE, but suggests against scheduled delivery with discontinuation of prophylactic-dose LMWH compared with allowing spontaneous labor. (ASH 2018 pregnancy VTE guideline)
- ASRA recommends at least 12 hours after low-dose LMWH and at least 24 hours after high-dose LMWH before neuraxial needle placement. ASRA says its recommendations should be applied to parturients, while allowing that urgent high-risk cases may require individualized exceptions. (ASRA fifth-edition regional anesthesia guideline)
- NHS SPS advises monitoring breastfed infants for rare bruising or unusual bleeding and limits its recommendations to healthy, full-term infants. (NHS SPS: Using heparins during breastfeeding)
- DailyMed says the benzyl alcohol in the multiple-dose vial may cross the placenta and states that preservative-free formulations should be used where possible if enoxaparin is needed during pregnancy. (DailyMed: enoxaparin sodium injection label)
General research, not specific to pregnancy.
EMA's 2021 review said a causal link between enoxaparin and acute generalized exanthematous pustulosis was a reasonable possibility and recommended changes to product information. In 2023, PRAC asked enoxaparin manufacturers to assess angiokeratoma in a future periodic safety report; this was a request for further assessment, not a conclusion that enoxaparin caused it.
- In November 2021, PRAC considered a causal relationship between enoxaparin and acute generalized exanthematous pustulosis to be at least a reasonable possibility and recommended amending product information. (EMA CHMP scientific conclusions for enoxaparin, 11 November 2021)
- In April 2023, PRAC requested assessment of angiokeratoma in the next periodic safety report for enoxaparin; the record does not state a causal conclusion. (EMA PRAC recommendations on signals, 11-14 April 2023)
- DailyMed: enoxaparin sodium injection labelDrug company labelTertiary
- Lepercq et al., BJOG 2001, retrospective pregnancy cohortUS governmentPrimaryIndependent check
- Rowan et al., American Journal of Obstetrics and Gynecology 2001US governmentPrimaryIndependent check
- LactMed: EnoxaparinUS governmentSecondaryPage dated 2025-11-15
- Guillonneau et al., breastfeeding during maternal enoxaparin treatmentUS governmentPrimary
- NHS SPS: Using heparins during breastfeedingUK governmentSecondaryPage dated 2024-01-19Independent check
- ACOG Practice Bulletin No. 196: Thromboembolism in PregnancyProfessional societySecondaryIndependent check
- ASH 2018 pregnancy VTE guidelineUS governmentSecondaryIndependent check
- ASRA fifth-edition regional anesthesia guidelineSecondaryPage dated 2025-09-16Independent check
- EMA CHMP scientific conclusions for enoxaparin, 11 November 2021EU agencySecondaryPage dated 2021-11-11European guidance
- EMA PRAC recommendations on signals, 11-14 April 2023EU agencySecondaryPage dated 2023-05-08European guidance
Last reviewed 2026-10-16
Independent check 2026-10-16
Not yet clinician-reviewed
Ask your provider about your situation.
Similar medications
- Dalteparin
- Heparin