Characterised by:
1st trimester exposure: Chondrodysplasia punctata (mild form)
Nasal hypoplasia (severe form)
2nd/3rd trimester exposure: Optic atrophy & mental retardation
Risk to the fetus varies b/w 4-7%
Fetal risk is dose-dependent & embryopathy is most severe when exposure occurs b/w 6-12 weeks of pregnancy
Fetal risk has been found to be low if the maternal warfarin dose is less than 5mg. But, the fetus is unavoidably overdosed compared with its mother because the fetal liver produces small amounts of vitamin K dependent clotting factors and the molecules of maternal procoagulants are too large to cross the placental barrier.
This risk has been showed to be reduced or rather eliminated by the use of UFH b/w 6-12 weeks of pregnancy
