Distribution of diandric and digynic triploidy depending on gestational age.

PURPOSE: To establish the distribution of diandric and digynic triploidy depending on gestational age. METHODS: 107 triploid samples tested prospectively in a single genetic department during a four-year period were analyzed for parental origin of triploidy by Quantitative Fluorescent Polymerase Chain Reaction (QF-PCR) (n=95) with the use of matching parental samples or by MS-MLPA (n=12), when parental samples were unavailable. Tested pregnancies were divided into three subgroups with regard to the gestational age at spontaneous pregnancy loss: <11 gestational weeks, 11-14 gestational weeks, and >14 gestational weeks. RESULTS: Diandric triploidy constituted overall 44.9% (46.5% in samples miscarried <11 gestational weeks, 64.3% in samples miscarried between 11 and 14 gestational weeks, and 27.8% in pregnancies which survived >14 gestational weeks). CONCLUSIONS: The distribution of diandric and digynic triploidy depends on gestational age. The majority of diandric triploid pregnancies is lost in the first trimester of pregnancy. In the second trimester, diandric cases are at least twice less frequent than digynic ones.

Usefulness of methylation-specific multiplex ligation-dependent probe amplification for identification of parental origin of triploidy.

Triploidy is a genetic aberration resulting from an extra haploid set of chromosomes of paternal (diandric) or maternal (digynic) origin. Diandric cases, opposite to digynic ones, may lead to gestational trophoblastic neoplasia (GTN) or generate maternal complications, therefore their identification is crucial, but reproducibility of traditionally used histopathological assessment is poor. The aim of the study was to analyse the usefulness of methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) with probes for two differentially methylated regions (DMR) at chromosome 11p.15.5 for identification of the parental origin of triploidy. 84 triploid DNA samples were tested with MS-MLPA: 34 paternal cases (40.5%) and 50 maternal ones (59.5%) according to the reference results of QF-PCR. Methylation ratio (MR) was calculated. Reference values proposed by the MRC-Holland for diploid samples (MR 0.8-1.2) were used. The values outside these ranges were used to diagnose parental origin of triploidy-paternal (MR > 1.2) or maternal (MR < 0.8). The effectiveness of MS-MLPA was 94.0%. The mean MR in paternal triploidy was 1.7 (SD-0.25; n = 34) compared with 0.56 in maternal triploidy (SD-0.12; n = 50). MR values in paternal and maternal triploidy did not overlap. In five samples (6.0%) parental origin of triploidy could not be accurately established by MS-MLPA, probably due to the maternal cell contamination (MCC). MS-MLPA can be used as a convenient method for distinguishing between paternal and maternal triploidy without the necessity for parental samples testing. It enables adequate selection of the paternal triploid cases for follow up in order to exclude post-molar GTN.