What fetal medicine specialists should know about the monochorionic placenta

Birth of a Healthy Monozygotic Twin Foal with Hydrops and a Dead Co-Twin

Transfer of in vitro-produced (IVP) equine embryos is associated with a higher incidence of monozygotic multiple pregnancies, but this remains a rarity. The outcome of monozygotic twin gestation is poor, and good management techniques are lacking. In addition, hydrops conditions are exceptional in horses, with hydroallantois occurring more frequently than hydramnion. Most hydrops conditions will lead to compromise or death of the foal and mare. A 6-year-old multiparous standardbred recipient mare, 332 days pregnant, diagnosed with a monozygotic twin and hydrops with a dead co-twin, gave birth with an assisted vaginal delivery. The dead foal, previously determined at 9 months by ultrasound, turned out to have the dimensions and hair corresponding to an 8-month-old foal. The other foal was born alive and considered healthy and normal-sized for its age. Both mare and foal were discharged from the clinic one week after parturition. This report is the first to describe the birth of a healthy foal born from a monozygotic twin pregnancy in the presence of hydrops, following transfer of a single IVP equine embryo. In addition, it is rare to find a non-macerated, non-mummified dead co-twin after fetal death at 8 months together with a healthy full-term foal.

Counselling in Fetal Medicine: Complications of Monochorionic Diamniotic Twin Pregnancies

Twin pregnancies are at increased risk of morbidity and mortality compared to singletons. Among all twins, monochorionic pregnancies are at higher risk of specific and non-specific complications compared to dichorionic pregnancies. Therefore, it is of great importance to properly counsel future parents with monochorionic pregnancies regarding the risks of adverse outcomes and the modalities of monitoring and intervention of the potential complications. Conditions related to the monochorionicity include twin-to-twin transfusion syndrome (TTTS), twin reversed arterial perfusion sequence (TRAP), and twin anemia polycythemia syndrome (TAPS); other complications include selective fetal growth restriction (sFGR) and congenital anomalies. This review aims to summarize the information available in the current literature regarding the complications in monochorionic diamniotic twin pregnancies, including outcomes and guideline recommendations about the clinical surveillance, management, and timing of interventions of these conditions that should be included in counselling in routine clinical practice.

The High-Risk Profile of Selective Growth Restriction in Monochorionic Twin Pregnancies

The present review aims to provide a critical appraisal of the sonographic diagnosis and follow-up and to evaluate the optimal clinical management of monochorionic twin pregnancies where one of the twins is complicated by selective fetal growth restriction (sFGR). The classification is based on the umbilical artery (UA) diastolic flow reflecting the outcome. If the sFGR twin has positive diastolic flow (Type I) then the prognosis is good, and it does not require close surveillance. Biweekly or weekly sonographic and Doppler surveillance and fetal monitoring are recommended strategies to detect unpredictable complications in type II and type III forms, which are defined by persistently absent/reverse end-diastolic flow (AREDF) or cyclically intermittent absent/reverse end-diastolic flow (iAREDF) in the umbilical waveforms, respectively. The latest forms are associated with an increased risk of unexpected fetal demise of the smaller twin and 10-20% risk of neurological injury in the larger twin in addition to the overall risk of prematurity. The clinical course can be affected by elective fetal therapy ('dichorinization' of the placenta with laser or selective fetal reduction) or elective delivery in the presence of severe fetal deterioration. The prediction of the clinical outcome in complicated cases of type II and III sFGR cases remains elusive. Novel routines in fetal and placental scans in order to predict neurological impairments and unexpected fetal death to optimize the delivery time-point are needed.

Are there differences between monochorionic twin placentas after spontaneous and assisted conception?

INTRODUCTION

No data are available on the placental characteristics of monochorionic twin pregnancies conceived by in vitro fertilization (IVF). This study investigates the differences between placentas from monochorionic diamniotic (MCDA) twin pregnancies conceived spontaneously and those conceived after IVF.

METHODS

This is a retrospective analysis of placental data from a consecutive series of MCDA twin pregnancies followed from the first trimester. The following placental characteristics were compared between IVF versus spontaneous MCDA pregnancies: placental sharing and birth weight discordance relative to placental sharing, the placental angioarchitecture (number, type, and size of anastomoses), and the umbilical cord insertion types.

RESULTS

Of the 256 MCDA placentas included in this analysis, 32 (12%) were conceived through IVF and 224 (88%) spontaneously. MCDA twin placentas after IVF did not differ significantly from MCDA twin placentas after spontaneous conception regarding placental sharing, birthweight discordance relative to sharing discordance, and angioarchitecture. There was a trend toward more discordant cord insertions (combination eccentric and velamentous) in IVF (25%) than in spontaneously conceived placentas (12%) (P = 0.05).

DISCUSSION

No differences could be demonstrated between MCDA placentation after spontaneous conception and IVF. Any differences in pregnancy outcome between spontaneous and IVF conceived MCDA twins may not be related to differences in placental sharing, angioarchitecture and cord insertion type.