This document discusses anticoagulation options during pregnancy for conditions requiring it, such as mechanical heart valves or blood clotting disorders. It describes that warfarin, unfractionated heparin, and low-molecular weight heparin are the three most common agents considered. While warfarin is very effective, it can harm the fetus if used in early pregnancy. Unfractionated heparin and low-molecular weight heparin do not cross the placenta and are safer options for early pregnancy, with low-molecular weight heparin requiring anti-Xa level monitoring. The document provides guidelines for using warfarin or heparins based on the trimester and any needed dose

1. Anticoagulation during
pregnancy
Dr. Sayeedur Rahman Khan Rumi
MD Cardiology Final Part Student
National Heart Foundation Hospital & Research Institute

2. Conditions requiring anticoagulation during
pregnancy include -
• Mechanical prosthetic heart valves
• Chronic atrial fibrillation
• Acute venous thromboembolism
• Eisenmenger syndrome
• Antiphospholipid antibody syndrome, and
• Inherited deficiencies predisposing to
thromboembolism

3. The three most common agents considered for use
during pregnancy are –
• Unfractionated heparin (UFH),
• Low-molecular-weight heparin (LMWH)
• Warfarin

4. Warfarin
• Warfarin freely crosses the placental barrier and can
adversely affect fetal development.
• It has been associated with a high incidence of
spontaneous abortion, prematurity, still birth, and fetal
bleeding.
• Warfarin can cause neonatal intracranial hemorrhage
or a retroplacental hematoma.
• Warfarin is considered safe during breast-feeding.

5. • Warfarin is the most effective anticoagulant for
preventing maternal thromboembolic events
during pregnancy.
• The risk of thromboembolic events using warfarin
throughout pregnancy is <4%, compared with 33%
with the use of UFH throughout pregnancy.
• Warfarin is an FDA class X during the first trimester
and is best considered a class B drug for the
remainder of pregnancy.

6. Warfarin Embryopathy Syndrome
• Fetal bone and cartilage
formation abnormalities
• Facial abnormalities,
optic atrophy, digital
abnormalities, epithelial
changes, and mental
impairment.
• Incidence: 4% to 10%
• The risk is highest when
warfarin is administered
during the 6th - 12th
week of gestation.
• The risks are dose-
dependent, a dose of < 5
mg daily have the lowest
risks (3%).

7. Unfractionated heparin
• UFH does not cross the placenta, and does not
have any teratogenic effects.
• Associated with -
Maternal osteoporosis
Hemorrhage
Thrombocytopenia, or thrombosis (HITT)
High incidence of thromboembolic events with
older generation mechanical valves
• Route: IV / SC
• Dose: based on an activated partial thromboplastin
time (aPTT) of 2 to 3 times the control level

8. Low-molecular-weight heparin
• Its advantages over UFH –
More predictable anticoagulant response
Lower incidences of HITT and osteoporosis.
• It does not cross the placenta
• SC twice-daily dosing
• It is essential to monitor anti-Xa levels. (The
4-hour-post dose target anti-Xa level varies
between 0.7 to 1.2)

9. 2014 AHA/ACC Guideline for the
Management
of Patients With Valvular Heart Disease:
Prosthetic Valves in Pregnancy

10. CLASS I
• Therapeutic anticoagulation with frequent monitoring is
recommended for all pregnant patients with a
mechanical prosthesis. (Level of Evidence: B)
• Warfarin is recommended in pregnant patients with a
mechanical prosthesis to achieve a therapeutic INR in the
second and third trimesters. (Level of Evidence: B)
• Discontinuation of warfarin with initiation of intravenous
UFH (with an activated partial thromboplastin time [aPTT] >2 times
control) is recommended before planned vaginal delivery
in pregnant patients with a mechanical prosthesis. (Level
of Evidence: C)
• Low-dose aspirin (75mg to 100mg) once per day is
recommended for pregnant patients in the second and
third trimesters with either a mechanical prosthesis or
bioprosthesis. (Level of Evidence: C)

11. CLASS IIa
• Continuation of warfarin during the first trimester is
reasonable if the dose of warfarin to achieve a
therapeutic INR is 5 mg per day or less. (Level of
Evidence: B)
• Dose-adjusted LMWH at least 2 times per day (with a
target anti-Xa level of 0.8 U/mL to 1.2 U/mL, 4 to 6 hours
postpose) during the first trimester is reasonable if the
dose of warfarin is >5 mg/day to achieve a therapeutic
INR. (Level of Evidence: B)
• Dose-adjusted continuous intravenous UFH (with an aPTT
at least 2 times control) during the first trimester is
reasonable if the dose of warfarin is >5 mg/day to
achieve a therapeutic INR. (Level of Evidence: B)

12. CLASS IIb
• Dose-adjusted LMWH at least 2 times per day (with a
target anti-Xa level of 0.8 U/mL to 1.2 U/mL, 4 to 6 hours postdose)
during the first trimester may be reasonable if the dose
of warfarin is ≤5 mg/day to achieve a therapeutic INR.
(Level of Evidence: B)
• Dose-adjusted continuous infusion of UFH (with aPTT at
least 2 times control) during the first trimester may be
reasonable if the dose of warfarin is ≤5 mg/day to
achieve a therapeutic INR. (Level of Evidence: B)

13. CLASS III: Harm
• LMWH should not be administered to pregnant
patients with mechanical prostheses unless anti-Xa
levels are monitored 4 to 6 hours after administration
(Level of Evidence: B)

14. Thank you