Monozygotic twins with discordant karyotypes following preimplantation genetic screening and single embryo transfer: case report

Purpose

To report a case of monozygotic monochorial diamniotic twins with discordant karyotypes.

Methods and results

The pregnancy was achieved following a treatment cycle with intracytoplasmic sperm injection (ICSI) and preimplantation genetic screening (PGS) for chromosomes X, Y, 13, 16, 18, 21, 22. One embryo euploid for studied chromosomes was transferred. Prenatal ultrasonography revealed monozygotic twins. One fetus had growth retardation, multiple organ abnormalities and polyhydramnion. The other twin had normal ultrasound appearance. Delivery on week 29 of gestation resulted in the birth of two females, a stillborn twin with karyotype 45,XX,-13[12]/46,XX,r(13)[3] and a healthy twin with normal karyotype.

Conclusions

The discordance in the twins’ karyotypes originated from a mosaic embryo. Structural chromosomal abnormality of the affected twin could not be revealed using standard PGS investigation. Embryo splitting occurred probably due to apoptotic process in an early stage of embryo development. Apoptosis represents one of the possible mechanisms which can explain the embryo twinning process globally.     

Placental apoptosis in discordant twins

OBJECTIVE: To investigate placental apoptosis in discordant dichorial twins. METHODS: Placental samples were obtained from 7 third-trimester suitable twins. Discordancy was defined as a >25 per cent difference in newborn birth weight. Light microscopy using hematoxylin and eosin (H&E)-stained paraffin slides and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling (TUNEL) methods were used to confirm the incidence of apoptosis. Investigators were blinded to pregnancy outcome. RESULTS: Both methods revealed that the incidence of apoptosis in the placentas of the smaller fetuses was significantly higher than in placentas of the larger fetuses. The incidence of TUNEL-positive cells in the former was 1.4+/-0.26 per cent: this was significantly higher than the incidence of apoptosis in the placental specimens of the latter (0.9+/-0.07 per cent, P< 0.02 Wilcoxon rank test). The same results were obtained with H&E: the incidence of apoptosis detected in placentas from the former was 1.07+/-0.1 per cent compared to 0.72+/-0.08 per cent in those of the latter (P< 0.02 Wilcoxon rank test). CONCLUSIONS: Despite similar environment conditions, placental apoptosis is increased in the smaller fetus and thus might play a role in discordancy between twins. Since increased placental apoptosis has also been found in singleton intrauterine growth restriction, this supports the hypothesis that the smaller twin is selectively growth restricted.     

Monozygotic twins discordant for trisomy 13

Monozygotic twins with discordant karyotypes are rare. We report a case of monozygotic twins discordant for trisomy 13 by amniocyte karyotypes. Ultrasound revealed multiple congenital anomalies in Twin A (47,XY,+13), none in Twin B (46,XY), and monochorionic-diamniotic placentation. Zygosity testing performed both prenatally and after birth supported monozygosity. Twin A died in the neontal period. Twin B survived and had normal physical examination, but peripheral blood karyotype revealed 20% mosaicism for trisomy 13. Monochorionic-diamniontic placentation with vascular anastomoses was confirmed by pathological examination. In this paper, we discuss the various mechanisms by which monozygotic twins may have discordant karyotypes. The surviving twin, structurally and developmentally normal at 6 months of age, will be monitored for potential complications of uniparental disomy of chromosome 13 and trisomy 13 mosaicism.     

Trisomy 18 in monozygotic twins with discordant phenotypes.

The incidence of trisomy 18 in monozygotic twins is approximately 1 per million. We report a pair of liveborn monozygotic twins with trisomy 18. Both twins had esophageal atresia with tracheoesophageal fistula (type C) and intrauterine growth retardation. Twin A had cleft lip, choanal atresia and perimembranous ventricular septal defect. Twin B had hypoplastic left heart syndrome. The twins died without aggressive intervention at the age of 2 months and 52 hours, respectively. These 2 babies had significantly discordant phenotypes, which suggests an epigenetic or environmental effect. Bioethical considerations remain important in the care of babies with multiple congenital anomalies.     

Managing twins discordant for fetal anomaly

An excess of structural anomalies is observed in twins compared to singletons. Approximately 1-2% of twin pregnancies may face the dilemma of expectant management versus selective termination following diagnosis of an anomaly affecting only one fetus. If the option of selective fetocide is considered, the main variable determining the technique to achieve this aim is chorionicity. In a dichorionic pregnancy, passage of substances from one twin into the circulation of the co-twin is unlikely due to the lack of placental anastomoses, hence KCl can be injected safely into the circulation of the affected twin to produce fetal asystole. In monochorionic twin pregnancies, selective termination needs to be performed by ensuring complete and permanent occlusion of both the arterial and venous flows in the umbilical cord of the affected twin, in order to avoid acute haemorrhage from the co-twin into the dying fetus, which may lead to death or organ damage. Bipolar cord coagulation under ultrasound guidance is associated with approximately 70-80% survival rates.     

46,XY monozygotic twins with discordant sex phenotype

Objective: To analyze male and female sex differentiation in monozygotic twins.

Design: Retrospective study.

Setting: Multiple academic centers.

Patient(s): A pair of monozygotic twins.

Intervention(s): Skin and blood samples were obtained for DNA analysis and karyotyping.

Main Outcome Measure(s): Mutation within the SRY gene was analyzed by the polymerase chain reaction–single-stranded conformation polymorphism test. Monozygosity was ascertained by short tandem repeat analysis. Karyotypes were studied in blood and skin fibroblasts.

Result(s): SRY was present in both twins, but no mutations were detected in the SRY conserved motif. Monozygosity was confirmed by the use of short tandem repeat analysis in four loci: c-fms, thyroid peroxidase, von Willebrand factor, and tyrosine hydroxylase. The karyotype was 46,XY uniformly in both twins.

Conclusion(s): Monozygotic twins can develop discordant male and female phenotypes despite the presence of a common karyotype and despite the presence of intact testis-determining genes. In the present case, this could be due to mutation or to mosaicism involving occult 45,X cell lines in the dysgenetic gonads.     

双胎出生体重的影响因素及不同一性双胎的高危因素分析

目的 探讨双胎出生体重的影响因素及发生不同一性双胎的高危因素.方法 收集2000年1月至2009年12月在中山大学附属第三医院及2000年1月至2009年6月在中山大学附属第一医院住院分娩的834例双胎妊娠的临床资料,以双胎间出生体重差异≥25%为标准诊断不同一性双胎75例,采用协方差分析及非条件Logistic回归方法回顾性分析多种因素与双胎出生体重及不同一性双胎的关系.结果 本组资料不同一性双胎的发生率为8.99%(75/834).孕妇年龄、受孕方式、绒毛膜性质、妊娠期糖尿病、脐带附着情况均与双胎出生体重存在相关性(相应的P值分别为0.021、0.000、0.000、0.012、0.017),而妊娠期高血压疾病、产次以及胎儿是否为同性别与双胎出生体重无相关性(P＞0.05).非条件Logistic回归分析显示,妊娠期高血压疾病和单绒毛膜性质是不同一性双胎的高危因素,其OR值(95%CI)分别为2.600(1.566～4.316)、1.833(1.010～3.582).将孕妇年龄分为4个阶段,即＜25岁组(69例)、～30岁组(312例)、～35岁组(325例)、高龄组(≥35岁)(128例),各组双胎的平均出生体重分别为:(2205±483)g、(2347±406)g、(2381±439)g和(2352±455)g,除～35岁组与高龄组比较,双胎平均出生体重差异无统计学意义外(P＞0.05),其他各组两两比较,差异均有统计学意义(P＜0.05).将新生儿性别分类后发现:不同性别双胎中男胎(270例)的平均出生体重为(2416±514)g,同性别男胎292例,平均出生体重(2381±428)g,不同性别双胎中女胎270例,同性别女胎272例,平均出生体重分别为(2322±488)g和(2301±418)g.除了不同性别双胎中男胎的出生体重与同性别男胎的体重比较,差异无统计学意义(P＞0.05)外,其他各组两两比较,差异均有统计学意义(P＜0.05).结论 双胎妊娠如孕妇年龄小于25岁、单绒毛膜性质、脐带边缘或帆状附着或女性双胎,则双胎胎儿的出生体重明显下降;如为辅助生殖技术后妊娠或合并妊娠期糖尿病,则双胎胎儿的出生体重增加.双胎妊娠合并妊娠期高血压疾病或单绒毛膜性质时,应警惕双胎不同一性的发生.     

Selective fetocide reverses preeclampsia in discordant twins

OBJECTIVE: Preeclampsia occurs in some twin gestations in association with a placental disorder of one but not both fetuses, thereby placing both at risk. We investigated a novel method of treating preeclampsia in these pregnancies. STUDY DESIGN: Three patients with second trimester preeclampsia linked to a lethal condition in one twin were treated with selective fetocide in an effort to reverse preeclampsia. Two patients presented with twins discordant for severe fetal growth restriction, and 1 patient presented with Ballantyne syndrome and twins discordant for fetal hydrops. RESULTS: Preeclampsia resolved in all 3 patients, allowing continuation of the pregnancy for an additional 9 to 23 weeks before delivery of the remaining fetus. Resolution of preeclampsia occurred in a timeframe consistent with placental involution documented in similar clinical circumstances. CONCLUSION: Selective fetocide may be an option for treating preeclampsia in some twin pregnancies, presumably by causing involution of the pathologic placenta. Delivery is not the only cure for preeclampsia.     

Monoamniotic twins discordant for body stalk anomaly

Body stalk anomaly is a rare malformation. This anomaly in monozygotic twins is extremely unusual. We describe a case of monoamniotic pregnancy discordant for body stalk anomaly diagnosed at 11 weeks. Ultrasound showed a fetus with a large anterior abdominal wall defect, anomaly of the spine and no evidence of lower extremities and other with a normal morphology. As far as our concern, only three monoamniotic pregnancies discordant for this malformation were reported. Our case represents the fourth reported monoamniotic pregnancy discordant for body stalk anomaly with diagnosis made by ultrasound and the second diagnosed in the first trimester.     

Neonatal nucleated red blood cells in discordant twins

The objective of this study was to test the hypothesis that in discordant twins, the smaller infant has higher absolute nucleated red blood cell (RBC) count than the larger sibling. We compared absolute nucleated RBC counts, hematocrits, absolute leukocyte counts, absolute granulocyte counts, absolute lymphocyte counts, RBC counts and platelet counts obtained in the first 12 hours of life in 30 discordant twin sets. The smaller infant had a higher absolute nucleated red blood cell count and lower platelet counts than its larger sibling. Platelet counts correlated inversely with absolute nucleated RBC counts ( R(2) = 24.5%; p < 0.001) and absolute nucleated RBCs correlated directly with percent intertwin weight differences ( R(2) = 17.8%; p = 0.02). In discordant twins, the smaller infant has higher absolute nucleated RBC count and lower platelet counts than the larger sibling. We speculate that the hematologic alterations in the smaller fetus are linked to relative fetal hypoxia.     

Umbilical Doppler velocimetry prediction of discordant twins.

OBJECTIVE: To evaluate the role of umbilical Doppler velocimetry as a comprehensive test for the prediction of discordant twins. METHODS: The sets of twins were studied with duplex Doppler velocimetry for umbilical artery in third trimester. A systolic/diastolic ratio was measured for each twin. The average difference in the ratios between each twin > or = 0.4 was used to indicate abnormal test. Discordancy was identified when the birth weight difference of > 25%. RESULTS: Among the 52 sets of twin pregnancies studied, 40 sets of twins fulfilled the study criteria. Eight sets of twins were discordant (20%). The mean gestational age at delivery was 37.15 +/- 2.24 weeks (range 28 to 41 weeks). The test correctly identified 6 of the 8 growth discordant twins which had a sensitivity of 75%, specificity of 68.75%, and accuracy of 70%. CONCLUSION: Umbilical Doppler velocimetry is useful in prediction of discordant twins.     

Doppler ultrasonographic evaluation of twins discordant for Rh alloimmunization

Minimally invasive methods have been used successfully to diagnose and treat maternal red blood cell alloimmunization. We present a case of a dizygotic twin pregnancy discordant for the Rh allele. Serial Doppler ultrasonography helped to diagnose the fetus that was at-risk for anemia caused by Rh alloimmunization and to direct treatment.     

Selective termination in dichorionic twins discordant for congenital defect

Objective

To evaluate the perinatal outcome of selective termination in dichorionic twins discordant for congenital defect, performed at the Hospital General Universitario Gregorio Marañon.

Study design

Twenty-eight dichorionic twins with an anomalous fetus were included from May 2008 to February 2011. Intracardiac KCl (1–2 ml; 15 mEq/ml) under ultrasonographic guidance was used in all procedures. Congenital defect, gestational age at the procedure, incidence and perinatal outcome were retrieved.

Results

Selective termination was performed in 14 (50%) cases of structural defects with normal karyotype and in 14 (50%) cases of chromosomal abnormality, 13 of them (92.8%) trisomy 21. Median gestational age at the procedure was 17.8 weeks (range 14.5–24; SD 2.3), and 12 (42.8%) were performed before 18 weeks. The presenting fetus was terminated in 11 cases (39.3%). Selective termination was followed by the subsequent delivery of a viable infant in 27 out of 28 cases (96.4%). Fetal loss before 24 weeks occurred in 1 case (3.6%). Median gestational age at delivery was 38 weeks (range 24.1–40.1; SD 3.8). Twenty-four (88.9%) were delivered >34 weeks and 1 (3.7%) before 28 weeks.

Conclusion

Selective termination in dichorionic twins discordant for congenital defect is a safe procedure with low risk of unintended fetal loss. This option is a reasonable alternative to expectant management or termination of the whole pregnancy.     

Utility of Doppler velocimetry in correlating with outcomes in severe discordant twins.

Twin birth weight discordance is associated with poor perinatal outcome. Three cases of severe discordant twins were serially assessed by ultrasound biometry and the Doppler ultrasonography of both the middle cerebral artery (MCA) and umbilical artery (UA) to measure pulsatility index (PI), resistance index (RI), and the systolic and diastolic ratio (S/D ratio). The birth weight discrepancies in three cases are 38%, 69% and 68%, respectively. Doppler velocimetry revealed a discrepancy in the S/D ratio of MCA and UA more than 15%. Absent end-diastolic flow, or the brain sparing effect, was noted in three small twins. Cerebral-umbilical S/D ratio (CUR) (MCA/UA) of the twins was above 1 in large ones and below 1 in small ones. The small twin in case 3 expired after delivery. In conclusion, if the CUR of the S/D ratio of the fetus is below 1, the prognosis might be poor and fetal weight discordancy might be progressively larger.     

A case of discordant related abnormal karyotypes from chorionic villi and amniocytes.

A case of three discordant cell lines in prenatal diagnosis is described, of which two were abnormal related structural abnormalities of chromosome 11. One of the abnormal cell lines was seen in all metaphases examined from direct preparations of chorionic villi, the cultured preparations showing an apparently normal male karyotype; the other abnormal cell line was seen in conjunction with a normal cell line in cultured amniocytes. Prenatal diagnosis offered solely on chorionic villus sampling would have yielded a mistakenly normal result on the basis of established criteria for distinguishing true mosaicism from confined placental mosaicism.