GuidelinesOther guideline
Anticoagulation
The guidelines recommend management of common obstetric conditions at primary and referral level, based on local experience and evidence-based practice. They are not intended as strict protocols nor as standard operating procedures, but rather as a guide to safe effective management of common obstetric problems. The guidelines should be most useful to interns, medical officers and registrars.
Indications for full anticoagulation
- Mechanical heart valve replacement
- Atrial fibrillation
- Tight mitral stenosis (valve area <1 cm2)
- Dilated cardiomyopathy
- Primary pulmonary hypertension
- Known thrombophilias
- Thromboembolism during the pregnancy
- History of two or more previous episodes of thromboembolism
Full anticoagulation in pregnancy
- 4-13 weeks: heparin ±10 000 units 8 hourly SC
- 14-36 weeks: warfarin 2.5-10 mg daily orally
- 37-42 weeks: heparin ±10 000 units 8 hourly SC
Alternative full anticoagulation regimen
- This is preferred for women with venous thromboembolism, and may, in consultation with cardiologists, be considered for women with mechanical valves.
- Enoxaparin 1 mg/kg 12 hourly SC
- Keep anti-factor Xa levels at 1.0 - 1.2 U/mL (3 hours after injection)
Management of anticoagulated pregnant women
- Order a second trimester ultrasound scan (23 weeks) to exclude fetal abnormality
- The safest anticoagulation regimen for the woman with a mechanical valve replacement is warfarin
- For women on warfarin, ensure INR of 2.5 – 3.5 for those with mechanical valves, and INR 2.0 – 3.0 for women in atrial fibrillation.
- If on warfarin, admit to hospital at 36 weeks to switch her to heparin
- For women on heparin, monitor PTT daily at 12:00, and adjust to 2.0 - 2.5 x control. Blood for PTT must be taken at the same interval from the last dose of heparin, half-way between doses
- If on heparin or enoxaparin at term, discontinue these agents 24 hours before starting induction of labour or commencing elective caesarean section
- Do not give heparin during labour, unless specifically requested by a consultant or cardiologist
- Epidural and spinal anaesthesia are contraindicated
- Avoid cuts and tears at delivery if possible
- Ensure haemostasis during perineal suturing or at caesarean section
- Women fully anticoagulated on warfarin who present in labour may need caesarean section to protect the baby against intracranial bleeding. Give 2 units of fresh frozen plasma to prevent maternal intraoperative bleeding
- Restart pre-pregnancy warfarin on the first postnatal day but continue SC heparin until INR is within therapeutic range, then discharge with follow up arrangements
Notes on anticoagulants
- The teratogenic effect of warfarin is limited to between the 4 to 12 weeks gestation, resulting in a warfarin embryopathy.
- It may also result in spontaneous fetal cerebral bleeds in the 2nd trimester
- For acute bleeding resulting from warfarin use, the antidote is fresh frozen plasma 1-2 units. Vitamin K 5 mg IV takes effect in 6-12 hours
- Heparin/enoxaparin does not cross the placenta, but may (especially unfactionated heparin) cause maternal alopecia, osteoporosis and alopecia
- Heparin antidote is protamine sulphate: give 1 mg for each 50 units of the hourly dose of continuously administered heparin or 1 mg for each 100 units of the last intermittent dose. Dilute in 20 mL saline and give IV over 5 minutes