"How is antenatally diagnosed vasa previa managed? "

Vasa previa is a condition in which fetal blood vessels cross over or near the internal cervical os leaving the blood vessels  vulnerable to rupture. Risk factors for vasa previa include IVF, second trimester placenta previa, low lying placenta,bilobed and succenturiate -lobed placentas.

For cases of confirmed vasa previa in the third trimester the Royal College of Obstetricians and Gynaecologists (RCOG), suggests admission to a unit with appropriate neonatal facilities between 28 and 32 weeks of gestation, administration of corticosteroids for fetal lung maturity because of the risk of preterm delivery,  and elective caesarean section between 35 and 37 weeks of gestation.

The Society of Obstetricians and Gynaecologists of Canada suggests that all cases of vasa previa diagnosed antenatally should receive glucocorticoids at 28 to 32 weeks, and that consideration should be given to hospitalization at 30 to 32 weeks in a facility where appropriate neonatal services are available. In selected asymptomatic patients outpatient management may be an option if the patient has a long closed cervix on transvaginal sonography.

Hull and Resnick follow patients using transvaginal ultrasound  assessment of the cervical length weekly from at least 30 weeks. If  the cervical length remains  greater or equal to 2.5 cm out of hospital management continues. .Steroids are given at 34 weeks and the mother delivered between 34 and 35 weeks by cesarean section. Delivery at 34 to 35 weeks of gestation may balance the risk of perinatal death with the risks of infant mortality, respiratory distress syndrome, mental retardation, and cerebral palsy.

REERENCES:
1. Placenta praevia, placenta praevia accreta and  vasa praevia: diagnosis and management. RCOG Green-top Guideline No. 27.  Royal College of Obstetricians and Gynaecologists, 2011 
http://www.rcog.org.uk/files/rcog-corp/GTG27PlacentaPraeviaJanuary2011.pdf
2. Gagnon R, et. al., Maternal Fetal Medicine Committee.Guidelines for the management of vasa previa J Obstet Gynaecol Can. 2009 Aug;31(8):748-60. PMID: 19772710
http://sogc.org/wp-content/uploads/2013/01/gui231CPG0908.pdf
3. Hull AD and Resnick R. Placenta Previa, Placenta Accreta, Abruptio Placenta, and Vasa Previa. In: Creasy RK, Resnik R, Iams JD, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 6th ed. Philadelphia, Pa.: Saunders/Elsevier; 2009:729-730.
4. 2. Robinson BK, Grobman WA. Effectiveness of timing strategies for delivery of individuals with vasa previa. Obstet Gynecol. 2011 Mar;117(3):542-9.PMID:21343756