Monoamniotic Twin Studies

1.  Perinatal Outcome of Monoamniotic Twin Pregnancies, February 2009. 
http://journals.lww.com/greenjournal/fulltext/2009/02000/perinatal_outcome_of_monoamniotic_twin_pregnancies.17.aspx  (Full Article)

Abstact:  

OBJECTIVE: To study perinatal mortality and neonatal morbidity in a large cohort of monoamniotic twin pregnancies with special emphasis to the gestational age-specific mortality.
METHODS: The study included monoamniotic twin pregnancies delivered in 10 perinatal centers in the Netherlands between January 2000 and December 2007.
RESULTS: A total of 98 monoamniotic pregnancies were included. The perinatal mortality rate (20 weeks of gestation through 28 days of life) was 19%; after exclusion of fetuses with lethal anomalies, the rate was 17%. After 32 weeks of gestation, only two pregnancies were complicated by perinatal mortality (4%). The incidence of twin–twin transfusion syndrome was 6%. The incidence of congenital heart anomalies and cerebral injury was 4% and 5%, respectively.
CONCLUSION: The current incidence of perinatal mortality in monoamniotic twins is considerably lower than in previous decades, but it is still high and occurs throughout pregnancy.


2.  Heyborne  Study, Received for publication February 27, 2004; revised May 21, 2004; accepted June 2, 2004.  

Email us for a copy of this study. (Abstract below from:  http://www.ajog.org/article/S0002-9378%2804%2900637-4/abstract)

Abstract: 
STUDY DESIGN: This was a multicenter retrospective cohort analysis of 96 monoamniotic twin gestations from 11 university and private perinatal practices. Overall mortality rates were calculated. The risk of intrauterine fetal death and neonatal morbidity was compared among women who were observed as inpatients versus outpatients. 
RESULTS: The overall mortality rate from enrollment was 19.8% (mean gestational age at enrollment, 17.4 weeks). The perinatal mortality and corrected perinatal mortality rates were 15.4% and 12.6%, respectively. Eighty-seven women had both twins who were surviving at 24 weeks of gestation; 43 women were admitted electively for inpatient surveillance at a median gestational age of 26.5 weeks; the remainder of the women were followed as outpatients and admitted only for routine obstetric indications (median gestational age, 30.1 weeks). No intrauterine fetal deaths occurred in any hospitalized patient. The risk of intrauterine fetal death in women who were followed as outpatients was 14.8% (13/88) versus 0 for women who were followed as inpatients (P !.001). There also were statistically significant improvements in birth weight, gestational age at delivery, and neonatal morbidity for women who were followed as inpatients. 
CONCLUSION: We observed improved neonatal survival and decreased perinatal morbidity among women who were admitted electively for inpatient fetal monitoring.


3.  Case Report:  Cord entanglement in monchorionic monoamniotic twins.  Eserdag S, Zulfikaroglu E, Ozer A.  2010.
http://www.bmj.sk/2010/11112-11.pdf  (Full Article)
Abstract:  Monochorionic monoamniotic twin gestations have been associated with perinatal mortality rates as high as 28% to 47%.  Umbilical cord entanglements and knots, twin-to-twin transfusion syndrome, congenital anomalies, prematurity and intertwine locking during labor are responsible for their high perinatal morbidity and mortality.  We report here two cases of cord entanglements:  One of them associated with twin-to-twin transfusion syndrome with gross vascular anastomoses and a massive cord entanglement.  The other one was associated with cesarean section due to dystocia of cord entanglement o the second fetus after vaginal birth of the first one.  There is still no consensus in literature for the management and the mode of delivery of these rarely encountered cases.  Full Tex in free PDF www.bmj.sk.


4.  Monochorionic monoamniotic twins:  neonatal outcome.  L Cordero, A Franco and S D Joy.  Received 3 October 2005; Revised 8 December 2005; Accepted 19 December 2005; Published online 9 February 2006.
http://www.nature.com/jp/journal/v26/n3/full/7211457a.html  (Full Article)

Abstract: 
BACKGROUND: Monochorionic monoamniotic twins (MoMo) occur in one of 10 000 pregnancies. Cord entanglement, malformations, twin-to-twin transfusion syndrome (TTS) and prematurity are responsible for their high perinatal morbidity and mortality.
OBJECTIVE:  To report our experience with 36 sets of MoMo twins (1990 to 2005) and to provide updated information for counseling.
METHODS:  Chorionicity was determined by placental examination, gestational age and TTS clinically and by sonography. Intrauterine growth restriction (IUGR) was diagnosed with a twin-specific nomogram.
RESULTS:  Cord entanglement was observed in 15 pregnancies, but only one twin with entanglement and a true knot, experienced related morbidity. Four of 71 live births were IUGR. Malformations were diagnosed prenatally (one hypoplastic left heart and one body stalk) and postnatally (one vertebral anomalies-anal atresia-tracheoesophageal fistula-renal defect (VATER) and two lung hypoplasias). Twin-to-twin transfusion syndrome affected three sets of twins. Five twin sets delivered before 31, 19 sets at 31 to 32 and 12 sets at 33 to 34 weeks. Six of 71 (8%) twins died (four malformations, one TTS and one 26 weeks premature). Head ultrasounds in 59 of 65 survivors showed two (3%) periventricular leukomalacia, five (9%) Grade I–II intraventricular hemorrhage and 52 (88%) normal.
CONCLUSIONS:  Monochorionic monoamniotic twins remain a group at risk for cord entanglement, congenital malformations, TTS and prematurity. Although their neonatal mortality and morbidity is high, outcomes for survival are better than anticipated.


5.  Monoamniotic twin pregnancy, Henry Roque and Charles Lockwood, September 2011,
Email us for a copy of this study, abstract below from:  http://www.uptodate.com/contents/monoamniotic-twin-pregnancy?source=search_result&search=monoamniotic+twin+pregnancy&selectedTitle=1~10

Abstract:  

INTRODUCTION
Monoamniotic twin pregnancies result from division of a single fertilized oocyte. The fetal membranes consist of one amnion and one chorion (figure 1). These pregnancies are relatively rare and characterized by a high risk of fetal complications, which will be reviewed in the following discussion.
INCIDENCE


The incidence of monoamniotic twins is approximately 1 in 10,000 pregnancies. Monoamnionicity is the least common pattern of twin placentation, affecting only 1 to 5 percent of monozygotic twin gestations [1-3]. (See "Twin pregnancy: Prenatal issues", section on 'Incidence and epidemiology'.)
PATHOGENESIS
Timing of postfertilization division determines placentation in twins:
Diamniotic, dichorionic placentation occurs with division prior to the morula stage (within three days post fertilization).
Diamniotic, monochorionic placentation occurs with division between days 4 and 8 post fertilization.
Monoamniotic, monochorionic placentation occurs with division between days 8 and 12 post fertilization.
Division at or after day 13 results in conjoined twins.
The factors responsible for timing of egg division are not known.