When to consult a geneticist specialising in gestational trophoblastic disease.

BACKGROUND: Gestational trophoblastic disease comprises hydatidiform moles and a rare group of malignancies that derive from trophoblasts. Although there are typical morphological features that may distinguish hydatidiform moles from non-molar products of conception, such features are not always present, especially at early stages of pregnancy. Furthermore, mosaic/chimeric pregnancies and twin pregnancies make pathological diagnosis challenging while trophoblastic tumours can also pose diagnostic problems in terms of their gestational or non-gestational origin. OBJECTIVES: To show that ancillary genetic testing can be used to aid diagnosis and clinical management of GTD. METHODS: Each author identified cases where genetic testing, including short tandem repeat (STR) genotyping, ploidy analysis, next generation sequencing and immunostaining for p57, the product of the imprinted gene CDKN1C, facilitated accurate diagnosis and improved patient management. Representative cases were chosen to illustrate the value of ancillary genetic testing in different scenarios. OUTCOME: Genetic analysis of placental tissue can aid in determining the risk of developing gestational trophoblastic neoplasia, facilitating discrimination between low risk triploid (partial) and high risk androgenetic (complete) moles, discriminating between a hydatidiform mole twinned with a normal conceptus and a triploid conception and identification of androgenetic/biparental diploid mosaicism. STR genotyping of placental tissue and targeted gene sequencing of patients can identify women with an inherited predisposition to recurrent molar pregnancies. Genotyping can distinguish gestational from non-gestational trophoblastic tumours using tissue or circulating tumour DNA, and can also identify the causative pregnancy which is the key prognostic factor for placental site and epithelioid trophoblastic tumours. CONCLUSIONS AND OUTLOOK: STR genotyping and P57 immunostaining have been invaluable to the management of gestational trophoblastic disease in many situations. The use of next generation sequencing and of liquid biopsies are opening up new pathways for GTD diagnostics. Development of these techniques has the potential to identify novel biomarkers of GTD and further refine diagnosis.

Biallelic NLRP7 variants in patients with recurrent hydatidiform mole: A review and expert consensus.

Hydatidiform mole (HM) is an abnormal human pregnancy characterized by excessive growth of placental trophoblasts and abnormal early embryonic development. Following a first such abnormal pregnancy, the risk for women of successive molar pregnancies significantly increases. To date variants in seven maternal-effect genes have been shown to cause recurrent HMs (RHM). NLRP7 is the major causative gene for RHM and codes for NOD-like receptor (NLR) family pyrin domain containing 7, which belongs to a family of proteins involved in inflammatory disorders. Since its identification, all NLRP7 variants have been recorded in Infevers, an online registry dedicated to autoinflammatory diseases (https://infevers.umai-montpellier.fr/web/). Here, we reviewed published and unpublished recessive NLRP7 variants associated with RHM, scored their pathogenicity according to the American College of Medical Genetics classification, and recapitulated all functional studies at the level of both the patients and the conceptions. We also provided data on further variant analyses of 32 patients and genotypes of 36 additional molar pregnancies. This comprehensive review integrates published and unpublished data on NLRP7 and aims at guiding geneticists and clinicians in variant interpretation, genetic counseling, and management of patients with this rare condition.

Distinct microRNA profiles for complete hydatidiform moles at risk of malignant progression.

BACKGROUND: MicroRNAs are small noncoding RNAs with important regulatory functions. Although well-studied in cancer, little is known about the role of microRNAs in premalignant disease. Complete hydatidiform moles are benign forms of gestational trophoblastic disease that progress to gestational trophoblastic neoplasia in up to 20% of cases; however, there is no well-established biomarker that can predict the development of gestational trophoblastic neoplasia. OBJECTIVE: This study aimed to investigate possible differences in microRNA expression between complete moles progressing to gestational trophoblastic neoplasia and those regressing after surgical evacuation. STUDY DESIGN: Total RNA was extracted from fresh frozen tissues from 39 complete moles collected at the time of uterine evacuation in Brazil. In the study, 39 cases achieved human chorionic gonadotropin normalization without further therapy, and 9 cases developed gestational trophoblastic neoplasia requiring chemotherapy. Total RNA was also extracted from 2 choriocarcinoma cell lines, JEG-3 and JAR, and an immortalized normal placenta cell line, 3A-subE. MicroRNA expression in all samples was quantified using microRNA sequencing. Hits from the sequencing data were validated using a quantitative probe-based assay. Significantly altered microRNAs were then subjected to target prediction and gene ontology analyses to search for alterations in key signaling pathways. Expression of potential microRNA targets was assessed by quantitative real-time polymerase chain reaction and western blot. Finally, potential prognostic protein biomarkers were validated in an independent set of formalin-fixed paraffin-embedded patient samples from the United States (15 complete moles progressing to gestational trophoblastic neoplasia and 12 that spontaneously regressed) using quantitative immunohistochemistry. RESULTS: In total, 462 microRNAs were identified in all samples at a threshold of <1 tag per million. MicroRNA sequencing revealed a distinct set of microRNAs associated with gestational trophoblastic neoplasia. Gene ontology analysis of the most altered transcripts showed that the leading pathway was related to response to ischemia (P<.001). Here, 2 of the top 3 most significantly altered microRNAs were mir-181b-5p (1.65-fold; adjusted P=.014) and mir-181d-5p (1.85-fold; adjusted P=.014), both of which have been shown to regulate expression of BCL2. By quantitative real-time polymerase chain reaction, BCL2 messenger RNA expression was significantly lower in the complete moles progressing to gestational trophoblastic neoplasia than the regressing complete moles (-4.69-fold; P=.018). Reduced expression of BCL2 was confirmed in tissue samples by western blot. Immunohistochemistry in the independent patient samples revealed significantly lower cytoplasmic expression of BCL2 in the villous trophoblasts from cases destined for progression to gestational trophoblastic neoplasia compared with those that regressed, both with respect to staining intensity (optic density 0.110±0.102 vs 0.212±0.036; P<.001) and to the percentage of positive cells (16%±28% vs 49.4%±28.05%; P=.003). CONCLUSION: Complete moles progressing to gestational trophoblastic neoplasia are associated with a distinct microRNA profile. miR-181 family members and BCL2 may be prognostic biomarkers for predicting gestational trophoblastic neoplasia risk.

Intensified therapies improve survival and identification of novel prognostic factors for placental-site and epithelioid trophoblastic tumours.

BACKGROUND: Placental-site trophoblastic (PSTT) and epithelioid trophoblastic tumours (ETT) are the rarest malignant forms of gestational trophoblastic disease (GTD). Our prior work demonstrated that an interval of ≥48 months from the antecedent pregnancy was associated with 100% death rate, independent of the stage. Here, we assess whether modified treatments for these patients have increased survival and identify new prognostic factors. METHODS: The United Kingdom GTD database was screened to identify all PSTT/ETT cases diagnosed between 1973 and 2014. Data and survival outcomes from our prior patient cohort (1976-2006) were compared to our new modern cohort (2007-2014), when intensified treatments were introduced. RESULTS: Of 54,743 GTD patients, 125 (0.23%) were diagnosed with PSTT and/or ETT. Probability of survival at 5 and 10 years following treatment was 80% (95% CI 72.8-87.6%) and 75% (95% CI 66.3-84.3%), respectively. Univariate analysis identified five prognostic factors for reduced overall survival (age, FIGO stage, time since antecedent pregnancy, hCG level, mitotic index) of which stage IV disease (HR 6.18, 95% CI 1.61-23.81, p = 0.008) and interval ≥48 months since antecedent pregnancy (HR 14.57, 95% CI 4.17-50.96, p < 0.001) were most significant on multivariable analysis. No significant differences in prognostic factors were seen between the old and new patient cohort. However, the new cohort received significantly more cisplatin-based and high-dose chemotherapy, and patients with an interval ≥48 months demonstrated an improved median overall survival (8.3 years, 95% CI 1.53-15.1, versus 2.6 years, 95% CI 0.73-4.44, p = 0.·005). CONCLUSION: PSTT/ETT with advanced FIGO stage or an interval ≥48 months from their last known pregnancy have poorer outcomes. Platinum-based and high-dose chemotherapy may help to improve survival in poor-prognosis patients.

A case of intraplacental gestational choriocarcinoma; characterised by the methylation pattern of the early placenta and an absence of driver mutations.

BACKGROUND: Gestational choriocarcinoma is a rare malignancy believed to arise from the trophoblast cells of the placenta. Despite the frequently aggressive clinical nature, choriocarcinoma has been routinely curable with cytotoxic chemotherapy for over 50 years. To date little is known regarding the route to oncogenesis in this malignancy. METHODS: In a case of intraplacental choriocarcinoma, we have performed detailed genetic studies including microsatellite analysis, whole genome sequencing (WGS) and methylation analysis of the tumour and surrounding mature placenta. RESULTS: The results of the WGS sequencing indicated a very low level of mutation and the absence of any driver mutations or oncogene activity in the tumour. The methylation analysis identified a distinctly different profile in the tumour from that of the mature placenta. Comparison with a panel of reference methylation profiles from different stages of placental development indicated that the tumour segregated with the first trimester samples. CONCLUSIONS: These findings suggest that gestational choriocarcinoma is likely to arise as a result of aberrations of methylation during development, rather than from DNA mutations. The results support the hypothesis that gestational choriocarcinoma arises from a normally transient early trophoblast cell. At this point in development this cell naturally has a phenotype of rapid division, tissue invasion and sensitivity to DNA damaging chemotherapy that is very similar to that of the mature choriocarcinoma cell.

Diploid/triploid mixoploidy: A consequence of asymmetric zygotic segregation of parental genomes.

Triploidy is the presence of an extra haploid set of chromosomes and can exist in complete or mosaic form. The extra haploid set of chromosomes in triploid cells can be of maternal or paternal origin. Diploid/triploid mixoploidy is a unique form of triploid mosaicism that requires the aberrant segregation of entire parental genomes into distinct blastomere lineages (heterogoneic cell division) at the earliest zygotic divisions. Here we report on eight cases of diploid/triploid mixoploidy from our institution and conduct a comprehensive review of the literature. The parental origin of the extra set of chromosomes was determined in two cases; and, based on phenotypic evidence we propose the parental origin in the other cases. One case with complex mixoploidy appears to have a digynic origin in addition to the involvement of two different sperm. Of our eight cases, only one resulted in the birth of a live healthy child. The other pregnancies ended in miscarriage, elective termination of pregnancy, intrauterine fetal demise or neonatal death. A review of the literature and the results of our cases show that a preponderance of recognized cases of diploid/triploid mixoploidy has a digynic origin.

Absence of Maternal Methylation in Biparental Hydatidiform Moles from Women with NLRP7 Maternal-Effect Mutations Reveals Widespread Placenta-Specific Imprinting.

Familial recurrent hydatidiform mole (RHM) is a maternal-effect autosomal recessive disorder usually associated with mutations of the NLRP7 gene. It is characterized by HM with excessive trophoblastic proliferation, which mimics the appearance of androgenetic molar conceptuses despite their diploid biparental constitution. It has been proposed that the phenotypes of both types of mole are associated with aberrant genomic imprinting. However no systematic analyses for imprinting defects have been reported. Here, we present the genome-wide methylation profiles of both spontaneous androgenetic and biparental NLRP7 defective molar tissues. We observe total paternalization of all ubiquitous and placenta-specific differentially methylated regions (DMRs) in four androgenetic moles; namely gain of methylation at paternally methylated loci and absence of methylation at maternally methylated regions. The methylation defects observed in five RHM biopsies from NLRP7 defective patients are restricted to lack-of-methylation at maternal DMRs. Surprisingly RHMs from two sisters with the same missense mutations, as well as consecutive RHMs from one affected female show subtle allelic methylation differences, suggesting inter-RHM variation. These epigenotypes are consistent with NLRP7 being a maternal-effect gene and involved in imprint acquisition in the oocyte. In addition, bioinformatic screening of the resulting methylation datasets identified over sixty loci with methylation profiles consistent with imprinting in the placenta, of which we confirm 22 as novel maternally methylated loci. These observations strongly suggest that the molar phenotypes are due to defective placenta-specific imprinting and over-expression of paternally expressed transcripts, highlighting that maternal-effect mutations of NLRP7 are associated with the most severe form of multi-locus imprinting defects in humans.

NLRPs, the subcortical maternal complex and genomic imprinting.

Before activation of the embryonic genome, the oocyte provides many of the RNAs and proteins required for the epigenetic reprogramming and the transition to a totipotent state. Targeted disruption of a subset of oocyte-derived transcripts in mice results in early embryonic lethality and cleavage-stage embryonic arrest as highlighted by the members of the subcortical maternal complex (SCMC). Maternal-effect recessive mutations of NLRP7, KHDC3L and NLRP5 in humans are associated with variable reproductive outcomes, biparental hydatidiform moles (BiHM) and widespread multi-locus imprinting disturbances. The precise mechanism of action of these genes is unknown, but the maternal-effect phenomenon suggests a function during early pre-implantation development, while biochemical and genetic studies implement them as SCMC members or interacting partners. In this review article, we discuss the role of the NLRP family members and the SCMC proteins in the establishment of genomic imprints and post-zygotic methylation maintenance, the recent advances made in the understanding of the biology involved in BiHM formation and the wider roles of the SCMC in mammalian reproduction.

Molecular genotyping of placental site and epithelioid trophoblastic tumours; female predominance.

OBJECTIVE: To investigate a large series of placental site trophoblastic tumours (PSTT) and epithelioid trophoblastic tumours (ETT) and determine the relationship between their development and the type and sex of both the immediately antecedent and causative pregnancies. METHODS: The antecedent pregnancy was determined from patient records in 92 cases with a confirmed diagnosis of PSTT, ETT or mixed PSTT/ETT. In a subset of 57 cases, type and sex of the causative pregnancy was established by molecular genotyping of tumour tissue microdissected from formalin-fixed, paraffin-embedded blocks. RESULTS: The antecedent pregnancy was a normal live birth in 59 (64%) cases, a hydatidiform mole in 19 (21%) and other pregnancy loss in 14 (15%). Where the sex was recorded, 36 (78%) of 46 antecedent normal pregnancies were female, a significantly greater proportion than expected (p<0.0001). Genotyping of 57 cases found 15 (26%) to derive from hydatidiform moles while 42 (74%) arose in non-molar pregnancies. Where the causative pregnancy was non-molar, 38 (91%) tumours arose in female conceptions, significantly greater than expected (p<0.0001). Analysis of short tandem repeats on the X chromosome in three tumours with an XY chromosomal constitution confirmed that the X chromosome was maternal in origin. CONCLUSIONS: PSTT and ETT predominantly arise in female pregnancies but can develop in male pregnancies. A male derived X chromosome is not required for the development of these tumours. While these tumours are predominantly female it is not because most originate in complete hydatidiform moles.

A Novel Genetic Mutation in a Patient With Recurrent Biparental Complete Hydatidiform Mole: A Brief Report.

Recurrent hydatidiform moles are defined by the occurrence of two or more molar pregnancies in the same patient. Familial recurrent hydatidiform moles (FRHM) is a rare autosomal recessive condition where women have an inherited predisposition to have molar pregnancies. Genotyping demonstrated that they are diploid and biparental. We report a case of FRHM from Egypt with a history of 6 recurrent complete moles. Sequencing of the NLPR7 gene revealed a deleterious homozygous base change in exon 2, c.197G>A, which would result in a truncated protein p.W66*. To the best of our knowledge, this mutation has not been described before.

Atypical placental site nodule (APSN) and association with malignant gestational trophoblastic disease; a clinicopathologic study of 21 cases.

The WHO Classification of Gestational Trophoblastic Tumors classifies placental site nodule (PSN) as a benign tumor-like trophoblastic neoplasm. Cases of PSN with atypical features were described [atypical placental site nodule (APSN)] and we started registering APSN in our unit in 2005. The aim of this study is to present our initial experience with these lesions. The Trophoblastic Disease Unit database was searched to identify all patients who were either referred with, or on review were diagnosed with, APSN from September 2005 to May 2013. Case notes and the pathology findings for these patients were retrieved and reviewed. A total of 21 cases of APSN were included, 3 of which were associated with gestational trophoblastic neoplasm on follow-up or review. Malignant gestational trophoblastic disease was associated with 3/21 (14%) cases of APSN, either concurrently or developing/manifesting within 16 mo of APSN diagnosis. None of these patients had raised serum hCG levels either at presentation or follow-up. Presence of APSN should indicate a thorough clinical and radiologic investigation and follow-up if diagnosed on curettage specimens. With increased recognition of this entity and corresponding larger series with longer follow-up, more accurate patient counseling will be possible.

Mutations causing familial biparental hydatidiform mole implicate c6orf221 as a possible regulator of genomic imprinting in the human oocyte.

Familial biparental hydatidiform mole (FBHM) is the only known pure maternal-effect recessive inherited disorder in humans. Affected women, although developmentally normal themselves, suffer repeated pregnancy loss because of the development of the conceptus into a complete hydatidiform mole in which extraembryonic trophoblastic tissue develops but the embryo itself suffers early demise. This developmental phenotype results from a genome-wide failure to correctly specify or maintain a maternal epigenotype at imprinted loci. Most cases of FBHM result from mutations of NLRP7, but genetic heterogeneity has been demonstrated. Here, we report biallelic mutations of C6orf221 in three families with FBHM. The previously described biological properties of their respective gene families suggest that NLRP7 and C6orf221 may interact as components of an oocyte complex that is directly or indirectly required for determination of epigenetic status on the oocyte genome.

Histopathological and immunohistochemical features of early hydatidiform mole in relation to subsequent development of persistent gestational trophoblastic disease.

OBJECTIVE: To examine histomorphological and immunohistochemical findings in hydatidiform moles to determine whether any features can reliably predict clinical behavior. STUDY DESIGN: Blinded semiquantitative review of histological and immunohistochemical findings in cases of partial hydatidiform mole (PHM) (N = 50) and complete hydatidiform mole (CHM) which either spontaneously resolved (N = 50) or required chemotherapy (N = 50). Immunostains assessed included MLH1, MSH2, nm23, TERT, p53, EGFR, and CerbB2 based on previous data. RESULTS: There were marked morphological differences in various criteria between CHMs and PHMs, including the proportion of villi with abnormal trophoblast hyperplasia (29% vs. 6%, respectively). However, there were no significant differences in any morphological parameters between CHMs that spontaneously resolved and those that subsequently required chemotherapy. Similarly, there were no clinically useful differences regarding any immunostaining scores between CHM groups. CONCLUSION: Neither morphological nor immunohistochemical features can reliably predict subsequent requirement of chemotherapy in CHMs.

Management and survival of patients with FIGO high-risk gestational trophoblastic neoplasia: the U.K. experience, 1995-2010.

OBJECTIVE: To present survival rates of high-risk gestational trophoblastic neoplasia (GTN) (FIGO score > 7) patients treated between 1995 and 2010 in the U.K. Death due to GTN is largely confined to patients with high-risk disease. In the U.K. a national system ensures that all patients are treated at only 2 specialist centers: Charing Cross Hospital (CXH) in London and Weston Park Hospital (WPH) in Sheffield. STUDY DESIGN: A total of 196 high-risk patients were identified using the CXH and WPH GTN databases, based on the risk score at the time of presentation. RESULTS: In all, 140 CXH and 56 WPH high-risk patients were treated with EMA/CO (etoposide, methotrexate, actinomycin D alternating with cyclophosphamide and vincristine) and MEA (methotrexate, etoposide, actinomycin D), respectively. The FIGO score at presentation ranged from 6-23. Eight patients (7from WPH and 1 from CXH) who were treated prior to 2002 as high-risk based on their pre-2002 scoring scored a 6 using FIGO 2002. Two (1%) patients died within 4 weeks of starting treatment (early death), 12 (6%) relapsed, and 9 patients subsequently died due to drug resistance. The overall survival was 94%, with a median follow-up of 4.69 years. CONCLUSION: In the context of a national trophoblastic disease service, patients with high-risk GTN have an excellent prognosis with EMA/CO or MEA.

Practical guidelines of the EOTTD for pathological and genetic diagnosis of hydatidiform moles.

Hydatidiform moles are rare and thus most pathologists and geneticists have little experience with their diagnosis. It is important to promptly and correctly identify hydatidiform moles given that they are premalignant disorders associated with a risk of persistent gestational trophoblastic disease and gestational trophoblastic neoplasia. Improvement in diagnosis can be achieved with uniformization of diagnostic criteria and establishment of algorithms. To this aim, the Pathology and Genetics Working Party of the European Organisation for Treatment of Trophoblastic Diseases has developed guidelines that describe the pathological criteria and ancillary techniques that can be used in the differential diagnosis of hydatidiform moles. These guidelines are based on the best available evidence in the literature, professional experience and consensus of the experts' group involved in its development.

Mutations in NLRP7 and KHDC3L confer a complete hydatidiform mole phenotype on digynic triploid conceptions.

Digynic triploidy is classically associated with a severely growth restricted fetus and a small nonmolar placenta. However, in genotyping hydatidiform moles as part of clinical practice, we identified two digynic triploid conceptions presenting with histopathological features of classical complete hydatidiform mole (CHM). Both cases occurred in women with a history of previous molar pregnancies and no normal pregnancies. Pathological review and genotyping of other molar pregnancies in these cases showed them to be typical CHM with negative p57(KIP2) immunostaining of the cytotrophoblast cells and villous stroma and to be diploid but biparental, confirming a diagnosis of familial recurrent hydatidiform mole (FRHM). Mutation screening of NLRP7 had identified a homozygous duplication, leading to a truncated protein, in case 1 whereas mutation screening of KHDC3L (C6orf221) in case 2 showed both the proband and her sister to be compound heterozygotes for mutations in KHDC3L. The observation of a single digynic, triploid conception presenting as a CHM in women with FRHM, where other pregnancies are diploid and biparental, supports the hypothesis that the role of both NLRP7 and KHDC3L in pregnancy is in setting and/or maintaining the maternal imprint. Clinically, a diagnosis of FRHM should be considered in women with genetically unusual conceptions that are phenotypically CHM.

First confirmation by genotyping of transplacental choriocarcinoma transmission.

A mother developed multimetastatic gestational choriocarcinoma 13 months after delivery, and her infant died aged 11 months from the same tumor. The transplacental choriocarcinoma transmission was confirmed by genotyping. Henceforth, we recommend a 2-year maternal human chorionic gonadotropin follow-up after neonatal choriocarcinoma and extensive imaging if the human chorionic gonadotropin rises.

Mutations in NLRP7 are associated with diploid biparental hydatidiform moles, but not androgenetic complete moles.

BACKGROUND: NLRP7 (NALP7) has been identified as the major gene involved in the inherited predisposition to recurrent molar pregnancies, a rare recessive condition in which affected individuals have complete hydatidiform moles of diploid biparental origin (BiCHM). The role of NLRP7 in other types of molar pregnancy and reproductive wastage has not been conclusively demonstrated. The purpose of this study was to clarify this by identifying NLRP7 variation in two clinically well-defined groups of patients: women with recurrent BiCHM, and women with three or more recurrent complete hydatidiform moles of proven androgenetic origin (AnCHM). METHODS: Fluorescent microsatellite genotyping of molar tissue was used to establish a diagnosis of recurrent BiCHM (four novel cases) or recurrent AnCHM (nine women with multiple CHM). These two groups were subsequently screened for mutations in NLRP7 using DNA sequencing. Additional screening for non-pathological variants was performed in 21 previously published cases of recurrent BiCHM. Taqman genotyping was used to determine the frequency of novel NLRP7 variants in two control cohorts of Caucasian and Asian women with no adverse reproductive outcomes. RESULTS: Of the four novel cases with recurrent BiCHM, two were homozygous for mutations in NLRP7 while one was a compound heterozygote for a nonsense mutation and a pathological variant. No NLRP7 mutations or pathological variants were identified in the fourth case. None of the women with AnCHM carried any mutations or pathological variants of NLRP7. A single case of AnCHM was found to be heterozygous for a novel variant (R413Q). CONCLUSION: NLRP7 mutations do not represent a major cause of AnCHM.

Partial molar pregnancy after intracytoplasmic sperm injection occurring as a result of diploid sperm usage.

PURPOSE: Partial molar pregnancies are rare conceptions characterized by having 69 rather than 46 chromosomes, the additional chromosome complement usually occurring as a result of fertilization of the ovum by two sperm. Although assisted conception with intracytoplasmic sperm injection (ICSI) should prevent the development of a partial molar pregnancy, occasional cases have been described after assisted conception using ICSI. The objective of this study was to investigate the cause of partial molar pregnancy in a couple who had undertaken assisted conception with ICSI. METHODS: Fluorescent microsatellite genotyping of DNA from the couple and tissue from their partial molar pregnancy was performed in order to confirm diagnosis and investigate the origin of the additional chromosome set. RESULTS: Genotyping confirmed that the partial molar tissue was triploid with an additional chromosome complement from the father. Genotyping of additional loci proximal to the centromere demonstrated that the two paternal sets of chromosomes originated in a single sperm with a double complement of paternal DNA resulting from non-reduction at the second meiotic division. CONCLUSIONS: This study confirms that partial molar pregnancy may occur after assisted conception with ICSI and that this occurs as a result of fertilization with a diploid sperm.