Ultrasonographic criteria for the prenatal diagnosis of placental chorionicity in twin gestations

Monofetal death in multiple pregnancies: risks for the co-twin, risk factors and obstetrical management

The intrauterine death of one fetus in the case of multiple pregnancies can have an impact on the development of the surviving twin. Based on a single-centre retrospective personal study of 248 multiple pregnancies, 10 of which presented a monofetal intrauterine death, the authors observed the type of placentation, the age and cause of the death, the way in which pregnancy continued and the outcome of the surviving twin. This investigation also includes a review of published documents. Monochorial pregnancies were more frequently encountered in the case of monofetal death in utero. The etiology of the death was not always found and one surviving twin presented lesions as microcephaly convulsions and was retarded on a psychomotor level. In this series these complications did not exist when the pregnancy was bichorial. The authors conclude by demonstrating the major risk of fetal contamination for a live twin coexisting with a dead twin in the case on monochorial pregnancy. Other parameters (cause of death, gestational age at death, delay and duration of cohabitation), do not seem to be significant. It would appear to be of fundamental importance to establish an accurate diagnosis of placentation and to implement specific surveillance of monochorial pregnancies. A decision tree is suggested for use in the case of monofetal death.

Early and simple determination of chorionic and amniotic type in multifetal gestations in the first fourteen weeks by high-frequency transvaginal ultrasonography

OBJECTIVE

Our aim was to determine the chorionic and amniotic types in multifetal pregnancies with transvaginal ultrasonography at > or = 14 weeks' gestation.

STUDY DESIGN

Two hundred twelve multifetal pregnancies were scanned transvaginally at or before 14 weeks' gestation. The number of fetuses and the chorionic and amniotic type were determined ultrasonographically. Of the 212 patients, 54 were delivered at our institution, and 43 of these 54 had pathologic evaluation of the placenta. Ultrasonographic and pathologic correlation of the chorionic and amniotic type was assessed in this group.

RESULTS

Ultrasonographic evaluation of the 212 pregnancies demonstrated 64 twin, 87 triplet, 41 quadruplet, 18 quintuplet, 1 sextuplet, and 1 septuplet gestation. Nine of the twin pregnancies were monochorionic-diamniotic; two of the triplets were dichorionic-triamniotic, and four of the quadruplets were trichorionic-quadraamniotic. In the 43 patients with both ultrasonographic and pathologic assessment, there were 40 twins, five of which were monochoronic diamniotic type. All three triplets were trichorionic-triamniotic type. In all 43 transvaginal ultrasonography correctly predicted the chorionic and amniotic type as determined by the pathologic findings.

CONCLUSIONS

Transvaginal ultrasonography at < or = 14 weeks can easily and accurately determine the chorionic and amniotic type in multifetal pregnancies.

First-trimester genetic diagnosis in multiple pregnancy: principles and potential pitfalls

Both the principles of first-trimester genetic diagnosis in multiple pregnancy and the special considerations required to avoid potential diagnostic pitfalls are presented. The experience consisted of 65 cases of twins and one case of quadruplets. Dichorionic twins were recognized by sonography in 54 cases. Transabdominal aspiration was generally preferred to transcervical for obtaining chorionic tissue, although in two cases both approaches were used. Diagnostic error following erroneous sampling was reported in 3 out of 54 sets of dichorionic twins (5.5 per cent). When like-sex dichorionic twins cannot be differentiated by cytogenetic or DNA polymorphism studies, amniocentesis should be recommended to confirm the reliability of the result on chorionic tissue.