Antiphospholipid Syndrome Testing for Intrauterine Fetal Death

Diagnostic Criteria and Testing

IUFD at 16 weeks meets the clinical criteria for obstetric antiphospholipid syndrome, which is defined as fetal loss at or after 10 weeks' gestation, according to the American College of Rheumatology 1
The American College of Rheumatology specifically includes fetal death ≥10 weeks as one of the three obstetric manifestations that, combined with positive laboratory findings, establishes the diagnosis 1

Order the complete panel of three antiphospholipid antibodies, including lupus anticoagulant (LAC), anticardiolipin antibodies (aCL), and anti-β2-glycoprotein I antibodies (aβ2GPI), to fully characterize the antibody profile 2, 3
All three tests should be performed on the same sample to fully characterize the antibody profile 3
Positive results must be confirmed with repeat testing at least 12 weeks later to distinguish persistent from transient antibody positivity 2, 3
Triple positivity (LAC + aCL + aβ2GPI of the same isotype) indicates the highest risk of recurrent pregnancy complications 2, 3

The presence of lupus anticoagulant is the strongest predictor of adverse outcomes 3
The American College of Rheumatology recommends considering testing for SLE and other autoimmune conditions, given the high rate of co-occurrence with APS 1, 4
APS diagnosis has implications beyond pregnancy, including ongoing thrombotic risk requiring long-term management 1