Antiphospholipid Syndrome in Pregnancy
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Direct answer
Antiphospholipid syndrome is an autoimmune condition with persistent antiphospholipid antibodies and either vascular thrombosis or pregnancy morbidity. In pregnancy it causes recurrent miscarriage, fetal death after 10 weeks, early severe pre-eclampsia and placental insufficiency. Lupus anticoagulant, anticardiolipin and anti-beta2 glycoprotein I antibodies establish the diagnosis, and treatment is low-dose aspirin with heparin, with the heparin intensity set by thrombotic history.
What you must remember
- Diagnostic antibodies: lupus anticoagulant, anticardiolipin IgG or IgM, and anti-beta2 glycoprotein I antibody, persistent on repeat testing at least 12 weeks apart.
- Clinical criteria: thrombosis, or pregnancy morbidity such as three or more unexplained consecutive miscarriages before 10 weeks, one fetal death at 10 weeks or more, or preterm birth before 34 weeks from severe pre-eclampsia or placental insufficiency.
- Classification: the Sydney criteria, a revision of the Sapporo criteria published in 2006, remain the classic standard, and newer classification criteria also exist.
- Lupus anticoagulant: prolonged clotting time in phospholipid-dependent tests that does not correct on mixing.
- Obstetric therapy: low-dose aspirin plus prophylactic heparin for obstetric APS without thrombosis.
- Thrombotic APS: therapeutic heparin with aspirin, continued through pregnancy.
- Warfarin: avoided in pregnancy because it is teratogenic, so heparin is used instead.
- Postpartum: anticoagulation continues for about six weeks after delivery.
A pathway from suspicion to treatment
A 33-year-old with two early losses and a prolonged aPTT is referred before her next conception. Confirmation needs repeat antibody testing, and the phenotype decides whether she needs therapeutic heparin or prophylactic heparin with aspirin.
- Suspect in recurrent loss: test for antiphospholipid antibodies after recurrent unexplained losses or any thrombosis, and check for SLE.
- Repeat to confirm: repeat positive tests at least 12 weeks apart before labelling APS.
- Define the phenotype: separate thrombotic from obstetric APS, since treatment differs.
- Start therapy early: low-dose aspirin with heparin for obstetric APS, and therapeutic heparin where there is prior thrombosis.
- Monitor the fetus: serial growth scans and Doppler, since placental insufficiency can develop late.
- Continue postpartum: keep anticoagulation for about six weeks after delivery, and review the plan for future pregnancies.
Antenatal care for these women is shared between obstetric and haematology teams, and the plan is reviewed again before every future pregnancy.
Where the exam tries to catch you
APS questions test the diagnosis criteria and the choice of heparin over warfarin, rather than the pathophysiology alone.
- Trap: "Warfarin is the standard anticoagulant for APS in pregnancy." Correct: warfarin is teratogenic, so heparin is used throughout pregnancy.
- Trap: "Aspirin alone is enough for obstetric APS." Correct: obstetric APS is commonly treated with aspirin plus prophylactic heparin.
- Trap: "One positive antibody test confirms APS." Correct: persistence on repeat testing at least 12 weeks apart is required.
Frequently asked questions
What are the Sydney criteria for antiphospholipid syndrome?
The Sydney criteria require at least one clinical criterion, either vascular thrombosis or pregnancy morbidity, together with persistent lupus anticoagulant, anticardiolipin or anti-beta2 glycoprotein I antibodies. They were revised in 2006 and remain the classic standard, although newer classification criteria exist.
Which pregnancy losses count as obstetric morbidity in antiphospholipid syndrome?
Obstetric morbidity in antiphospholipid syndrome includes three or more unexplained consecutive miscarriages before 10 weeks, one fetal death at 10 weeks or more with a morphologically normal fetus, and preterm birth before 34 weeks from severe pre-eclampsia or placental insufficiency. Other causes must be excluded first.
What treatment is used for obstetric antiphospholipid syndrome?
Obstetric antiphospholipid syndrome without thrombosis is treated with low-dose aspirin and prophylactic heparin, usually low molecular weight heparin. Thrombotic antiphospholipid syndrome needs therapeutic heparin, and warfarin is avoided in pregnancy.
Why is warfarin avoided in antiphospholipid syndrome during pregnancy?
Warfarin is avoided in antiphospholipid syndrome during pregnancy because it is teratogenic, causing embryopathy when given in the early weeks. Heparin is preferred throughout pregnancy, and the decision is made with haematology and obstetric input.