There are three types of vasa previa. Types 1 and 2 were described by Catanzarite et al. In Type 1, there is a velamentous insertion with vessels running over the cervix. In Type 2, unprotected vessels run between lobes of a bilobed or succenturiate lobed placenta. In Type 3, a portion of the placenta overlying the cervix undergoes atrophy. In this type, there is a normal placental cord insertion and the placenta has only one lobe. However, vessels at a margin of the placenta are exposed. Risk factors
Vasa previa is seen more commonly with velamentous insertion of the umbilical cord, accessory placental lobes (succenturiate or bilobate placenta), multiple gestation, and in vitro fertilisation pregnancy. In IVF pregnancies, incidence as high as one in 300 has been reported. The reasons for this association are not clear, but disturbed orientation of the blastocyst at implantation, vanishing embryos and the increased frequency of placental morphological variations in IVF pregnancies have all been postulated. Diagnosis
The classic triad of the vasa praevia is: membrane rupture, painless vaginal bleeding and fetal bradycardia or fetal death. Prior to the advent of ultrasound, this diagnosis was most often made after a stillbirth or neonatal death in which the mother had ruptured her membranes, had some bleeding, and delivered an exsanguinated baby. In these cases, examination of the placenta and membranes after delivery would show evidence of a velamentous cord insertion with rupture of the vessels.
Because these patients are at risk for preterm delivery, it is recommended that steroids should be given to promote fetal lung maturation. When bleeding occurs, the patient goes into labor, or if the membranes rupture, immediate treatment with an emergency caesarean delivery is usually indicated. See also
Placenta praevia

References
External links

International Vasa Previa Foundation