Genetic causes of recurrent miscarriages.

Recurrent miscarriage is an important problem in reproductive health, which affects 1-5% of couples. The aim of this article is to summarize current knowledge on the genetic causes of recurrent miscarriage. It presents the most common parental genetic disorders (karyotype abnormalities, recessive diseases carrier status, dominant diseases and thrombophilia) connected with recurrent pregnancy loss, as well as research into other possible genetic causes. This review also sets out to demonstrate changes in the embryonic/fetal genome that may lead to abortions, and discusses the methods used to assess miscarried material, together with their advantages and disadvantages. Knowledge of the genetic background of miscarriages is important for prognosis, as well as the potential planning of prenatal diagnostics in subsequent pregnancies.

Prenatal karyotype results from 2169 invasive tests.

OBJECTIVES: Foetal karyotyping is a basic tool used to diagnose the most common genetic syndromes. Although new molecular methods such as FISH, MLPA or QF-PCR allow rapid prenatal testing, they are of limited value when diagnosing less frequent chromosomal abnormalities. Chromosomal microarray analysis offers higher test resolution than traditional karyotyping and has been recommended as first-line genetic testing in prenatal diagnosis. The aim of the study was to confirm whether foetal karyotyping remains a valid approach to prenatal diagnosis by analysing its performance in a large population of pregnant women with a high risk of chromosomal aberration. MATERIAL AND METHODS: An analysis was performed of 2169 foetal karyotypes from two referral university centres for prenatal diagnostics in Lodz, Poland. RESULTS: Amniocentesis and foetal karyotyping were performed when screening methods had indicated a high risk of chromosomal aberration, or when prenatal ultrasound had proved foetal abnormality. The study group included 205 (9.4%) abnormal foetal karyotypes. Rare aberrations were observed in 34 cases (e.g., translocations, inversions, deletions and duplication). A marker chromosome was present in five cases. CONCLUSIONS: One third of the chromosomal abnormalities observed in the prenatal tests were rarer aberrations (i.e., not trisomy 21, 18 or 13). As many of these could not be detected by the new molecular methods, foetal karyotyping remains an important component of prenatal diagnosis.

Prenatal Sonographic Features of Rare Chromosome 13 Aberrations.

Objective: Trisomy 13 is one of the most common chromosome aberrations diagnosed in the prenatal period, and is associated with some specific dysmorphic features. Rare chromosome 13 aberrations other than trisomy 13 may cause other fetal abnormalities. The aim of the study was to analyze cases with those rare chromosome 13 aberrations. Methods: We analyzed all prenatal tests performed in the Department of Clinical Genetics of the Medical University of Lodz from 2016 to 2021 to find all chromosome 13 aberrations. Results: The most common aberration of chromosome 13 was a simple trisomy 13 (n = 16). We found five rare chromosome 13 aberrations other than simple chromosome 13 trisomy: mosaic trisomy 13 mos 47,XX,+13[11]/46,XX[10], mosaic monosomy 13 mos 46,XY,-13,+mar[9]/46,XY[31], duplication 13q21.1-q31, deletion 13q34 and deletion 13q31.1-q34. The deletion 13q31.1-q34 occurred in monochorionic diamniotic twin pregnancy. Conclusion: Rare aberrations accounted for 24% of all chromosome 13 aberrations. Cases with mosaic monosomy of chromosome 13 and microdeletion 13q had similar abnormalities of the external genitalia and facial dysmorphia. The case with duplication 13q was very similar to the clinical features of chromosome 13 trisomy. Mosaic trisomy 13 can occur without any accompanying anatomical defects.

Cases of tetrasomy 9p and trisomy 9p in prenatal diagnosis-Analysis of noninvasive and invasive test results.

Objective: Tetrasomy 9p and trisomy 9p are rare chromosomal aberrations. The phenotypes of tetrasomy 9p and trisomy 9p are variable. Most cases are diagnosed in the postnatal period. The study aims to analyze the prenatal phenotype of tetrasomy 9p and trisomy 9p in terms of ultrasound and screening tests. Methods: A set of 1573 prenatal tests performed from 2016 to 2021 was reviewed to identify all cases with trisomy 9p and tetrasomy 9p. In four cases with 9p gain, non-invasive and invasive test results were analyzed. Results: Four cases with the 9p gain were diagnosed in the prenatal period: two cases with tetrasomy 9p and two cases with trisomy 9p. Nasal bone hypoplasia and ventriculomegaly are common features of 9p gain. In two out of four cases with the 9p gain, an increased risk of trisomy 21 was found in the combined first-trimester screening test. Conclusion: Trisomy 9p and tetrasomy 9p are characterized by a variable phenotype in the prenatal period, manifesting in genetically abnormal fetuses. The tetrasomy 9p and trisomy 9p may suggest trisomy 21 in the first trimester.

Occurrence of c.976 G>T (p.Val326Leu) and c.452 G>A (p.Trp151Ter) variants in DHCR7 gene in population of polish women with recurrent miscarriage.

INTRODUCTION: Recurrent miscarriage is a serious clinical problem that affects 1-5 % of all couples trying to conceive. Although the incidence of Smith-Lemli-Opitz Syndrome (SLOS, OMIM #270400), an autosomal recessive condition caused by variants in the DHCR7 gene, is very low, (1:83 000), the observed carrier frequency of DHCR7 gene variants in the Polish population is high, ranging from 1:24 to 1:31. It is possible that this carriage may be responsible for early pregnancy loss. OBJECTIVES: The aim of the study is to determine the carrier frequency of the p c.976 G>T (p.Val326Leu) and c.452 G>A (p.Trp151Ter) variants in the DHCR7 gene in patients experiencing recurrent miscarriage. METHODS: The study group included 480 patients: a study group of 380 with at least 2 miscarriages before the 20th week of pregnancy, and a control group of 100 who had not experienced miscarriage. The variants were identified by genotyping: c.976 G>T (p.Val326Leu) by the TaqMan® SNP Genotyping Assay system, and c.452 G>A (p.Trp151Ter) using the BfaI restriction enzyme. Statistical analysis was performed using R software. RESULTS: No examples of c.976 G>T (p.Val326Leu) were found in either group. c.452 G>A (p.Trp151Ter) was found in 22 participants from the study group and 4 from the control group; however, this difference was not significant (Chi2 test p = 0.61). CONCLUSIONS: Being a carrier of the c.976 G>T (p.Val326Leu) and c.452 G>A (p.Trp151Ter) variants in theDHCR7 gene is not a risk factor for recurrent miscarriage in the Polish population.