RT Book, Section
A1 Bianchi, Diana W.
A1 Crombleholme, Timothy M.
A1 D'Alton, Mary E.
A1 Malone, Fergal D.
SR Print(0)
ID 1106401476
T1 Monoamniotic Twins
T2 Fetology: Diagnosis and Management of the Fetal Patient, 2e
YR 2015
FD 2015
PB McGraw-Hill Education
PP New York, NY
SN 978-0-07-144201-5
LK obgyn.mhmedical.com/content.aspx?aid=1106401476
RD 2024/04/20
AB Key  PointsMonoamniotic  twinning  is  a  rare  form  of  twinning  where  both  twins  occupy  a  single  amniotic  sac.This  form  of  twinning  occurs  when  a  single  embryo  splits  during  postovulation  days  8  to  10.The  most  common  way  to  diagnose  monoamniotic  twins  antenatally  is  failure  to  visualize  a  dividing  membrane  in  the  presence  of  a  single  placental  mass  and  like-gender  twins.  During  the  first  trimester,  the  presence  of  two  embryos  in  a  single  sac,  but  with  only  one  yolk  sac,  is  highly  suggestive  of  monoamnionicity.These  pregnancies  are  at  risk  for  significant  perinatal  morbidity  and  mortality.  This  has  been  attributed  to  preterm  delivery,  intrauterine  growth  restriction,  congenital  anomalies,  vascular  anastomoses  between  twins,  and  umbilical  cord  entanglement  or  cord  accidents.Intense  antenatal  surveillance  and  timed  delivery  has  been  shown  to  improve  outcomes.  This  typically  takes  the  form  of  elective  hospitalization  with  daily  nonstress  testing  at  24  to  26  weeks’  gestation,  and  increased  frequency  of  testing  if  variable  decelerations  are  noted.Elective  delivery  at  32  to  34  weeks’  gestation  is  recommended  if  fetal  testing  remains  reassuring  and  cesarean  delivery  is  most  commonly  recommended.