Prenatal screening and diagnosis of aneuploidy in multiple pregnancies

Determining the cause of intrauterine fetal death in monochorionic twins: A case report

Background

Determining the cause of intrauterine fetal death is essential for patients to manage their next pregnancy. However, in the majority of cases of fetal death, the cause remains unexplained despite comprehensive evaluation, especially in the cases of twins. Among twin pregnancies, conditions of monochorionic twinning, commonly regarded as monozygotic, are more complicated than dichorionic ones.

Case summary

We systematically evaluated the cause of fetal death for a Han Chinese woman with monochorionic twinning following in vitro fertilization/embryo transfer. Discrepant karyotypes were unexpectedly discovered between the twins. One fetus had an aneuploid male karyotype (46, XY), dup (9) (p24.3-q13), and the other had a normal female karyotype (46, XX). We considered that the male died of aberration of chromosome 9 and the female died of subsequent acute exsanguination through vascular anastomosis.

Conclusion

This study demonstrated the importance of recognizing the presence of monochorionic dizygotic twinning and the challenges of clinical management for twins following in vitro fertilization/double embryo transfer.

Ultrasound screening for complications in twin pregnancy

In the decades since the introduction of ultrasound into routine obstetric practice, the advantages of ultrasound have moved beyond the simple ability to identify multiple pregnancies antenatally to the possibility of screening them for fetal anomalies, pre-eclampsia, preterm birth, and the complications specific to monochorionic pregnancies. Screening studies have often excluded twins because physiological differences impact on the validity and sensitivity of the screening tests in routine use in singletons, and therefore, the evidence of screening performance in multiple pregnancy lags behind the evidence from singleton pregnancies. In general, most pregnancy complications are more common in twin pregnancy, but screening tests are less accurate or well validated. In this review article we present the current state of the evidence and avenues for future research relating to the use of ultrasound and screening for complications in twin pregnancies, including the monochorionicity-related pathologies, such as twin-twin transfusion syndrome, selective growth restriction, twin anaemia-polycythaemia sequence and twin reversed arterial perfusion sequence.

Pregnancy associated plasma protein-A2: a novel biomarker for Down syndrome

INTRODUCTION

In an effort to improve prenatal screening for Trisomy 21, we evaluated pregnancy associated plasma protein-A2 (PAPP-A2) as a potential novel second trimester biomarker for Trisomy 21.

METHODS

Trisomy 21 and normal control mid-trimester placental samples were subjected to quantitative rt PCR analysis of seven genes we had previously found to be differentially expressed in Trisomy 21 placentae. The localization and differential expression of PAPP-A2 in second trimester placentae from normal and Trisomy 21 pregnancies was determined by immunohistochemistry. PAPP-A2 maternal serum protein levels in ten Trisomy 21 and ten diploid pregnancies were compared by Western blotting. Maternal serum PAPP-A2 levels were measured in 30 Down syndrome cases and 142 normal controls, using ELISA. Regression analysis was used to determine the correlation of PAPP-A2 with other existing markers of Trisomy 21.

RESULTS

PAPP-A2 (aka PLAC 3) mRNA and protein expression were both increased in Down syndrome placentae as compared to diploid placentae. PAPP-A2 was also increased in maternal serum from Down syndrome pregnancies as compared to diploid pregnancies. PAPP-A2 expression correlated weakly with established markers.

DISCUSSION

This work takes advantage of our previously performed systematic approach to the discovery of novel maternal serum biomarkers for Trisomy 21, using cDNA microarray analysis. Beginning with the validation of the microarray results, we have tracked PAPP-A2 overexpression in Down syndrome from placental mRNA to maternal serum protein.

CONCLUSION

PAPP-A2 could serve as an additional maternal serum marker in prenatal screening for Trisomy 21.