|Classification and external resources|
Vasa praevia (vasa previa AE) is an obstetric complication in which fetal blood vessels cross or run near the external orifice of the uterus. These vessels are at risk of rupture when the supporting membranes rupture, as they are unsupported by the umbilical cord or placental tissue.
Vasa previa is present when fetal vessels traverse the fetal membranes over the internal cervical os. These vessels may be from either a velamentous insertion of the umbilical cord or may be joining an accessory (succenturiate) placental lobe to the main disk of the placenta. If these fetal vessels rupture the bleeding is from the fetoplacental circulation, and fetal exsanguination will rapidly occur, leading to fetal death.
Vasa previa is seen more commonly with velamentous insertion of the umbilical cord, accessory placental lobes (succenturiate or bilobate placenta), multiple gestation, IVF pregnancy. In IVF pregnancies incidences as high as one in 300 have 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 in vitro fertilisation pregnancies have all been postulated.
- The classic triad of the vasa praevia is: membrane rupture, painless vaginal bleeding and fetal bradycardia.
- This is rarely confirmed before delivery but may be suspected when antenatal sono-gram with color-flow Doppler reveals a vessel crossing the membranes over the internal cervical os.
- The diagnosis is usually confirmed after delivery on examination of the placenta and fetal membranes.
- Alkali denaturation test detects the presence of fetal hemoglobin in vaginal blood, as fetal hemoglobin is resistant to denaturation in presence of 1% NaOH.
- Also detection of fetal hemoglobin in vaginal bleeding is diagnostic.
- Yasmine Derbala, MD; Frantisek Grochal, MD; Philippe Jeanty, MD, PhD (2007). "Vasa previa". Journal of Prenatal Medicine 2007 1 (1): 2–13.Full text
- Lijoi A, Brady J (2003). "Vasa previa diagnosis and management.". J Am Board Fam Pract 16 (6): 543–8. doi:10.3122/jabfm.16.6.543. PMID 14963081.Full text
- Lee W, Lee V, Kirk J, Sloan C, Smith R, Comstock C (2000). "Vasa previa: prenatal diagnosis, natural evolution, and clinical outcome.". Obstet Gynecol 95 (4): 572–6. doi:10.1016/S0029-7844(99)00600-6. PMID 10725492.
- Bhide A, Thilaganathan B (2004). "Recent advances in the management of placenta previa.". Curr Opin Obstet Gynecol 16 (6): 447–51. doi:10.1097/00001703-200412000-00002. PMID 15534438.
- Oyelese Y, Smulian J (2006). "Placenta previa, placenta accreta, and vasa previa.". Obstet Gynecol 107 (4): 927–41. doi:10.1097/01.AOG.0000207559.15715.98. PMID 16582134.
7. Textbook of Obstetrics by D.C. Dutta 7th edition, page 259