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1.
目的:分析自然流产史夫妇外周血染色体异常核型的种类及其在男女性中的分布特点。方法:检测2178对自然流产史夫妇外周血淋巴细胞染色体核型,分析比较染色体变异的种类、发生率及其在男、女性中的分布差异。结果:2178对(4356例)自然流产史夫妇中发现染色体异常539例(12.37%),其中男266例,女273例。染色体结构异常87例,其中相互易位最多见为58例(66.7%,58/87),有27例为世界首报染色体结构异常核型。其次为罗伯逊易位13例,倒位6例,插入、缺失等其他异常核型10例。染色体数目异常8例,包括2例标记染色体、1例XYY及5例不同类型的X染色体非整倍体嵌合。多态性改变444例中,D/G组染色体随体区变异最为多见,共271例(61.04%,271/444)。结论:自然流产史夫妇外周血染色体异常均有发生,男女性发生率并无明显差异,染色体异常以相互易位为主。染色体多态性发生率较高,对以自然流产史就诊的夫妇,有必要同时进行染色体检查,有助于病因的分析与诊断,并为临床咨询及后续生殖干预提供依据。  相似文献   

2.
The effect of translocations on embryo development was evaluated and results were compared in terms of embryo development with those of embryos obtained from standard intracytoplasmic sperm injection (ICSI) cycles. In 23 translocation carriers with 34 cycles, fertilization, pronuclear morphology scoring (PMS), developmental arrest, cleavage and blastocyst formation were evaluated and compared with embryos obtained from non-translocation cases undergoing ICSI (n = 98 cycles). In 28 cycles, preimplantation genetic diagnosis (PGD) was performed on prezygotes (first and second polar body biopsy for female carriers; n = 3) or on embryos having seven or more blastomeres (blastomere biopsy; n = 25). In six cycles for four couples, probes for translocated chromosomes were not available, so PGD could not be performed. Overall, in translocation cases, a lower fertilization rate, a higher rate of retarded embryo development, and a lower rate of blastocyst formation were observed compared with embryos of non-translocation cases. Fluorescence in-situ hybridization (FISH) analysis showed a 70.9% abnormality rate for reciprocal translocations and 55.0% for Robertsonian translocations respectively. In cases with Robertsonian and reciprocal translocation carriers, the probability of poor embryo development, which may be a result of high segregation abnormalities, may negatively affect the outcome of assisted reproductive techniques. This poor prognosis should also be considered when genetic counselling for translocation is given.  相似文献   

3.
OBJECTIVE: To determine whether the miscarriage rate in recurrent miscarriage patients with an abnormal karyotype, especially reciprocal translocations, in either partner is worse than without an abnormal karyotype. DESIGN: Retrospectively analyzed prospectively obtained database. SETTING: Nagoya City University Hospital. PATIENT(S): One thousand and two hundred eighty-four couples with a history of 2 or more (2 to 12) consecutive first-trimester miscarriages. INTERVENTION(S): Patients with antiphospholipid antibodies were treated with low-dose aspirin and combined therapy. MAIN OUTCOME MEASURE(S): Subsequent miscarriages were compared for cases with and without an abnormal karyotype in either partner. A karyotype analysis was also conducted for each aborted conceptus and offspring of 95 pregnancies of 47 patients with reciprocal translocations. RESULT(S): Of the total of 1,284 couples, 58 (4.5%) had translocations, 11 being Robertsonian translocations. Eleven of the 18 cases (61.1%) where the husband had a reciprocal translocation suffered further miscarriage; this also was the case for 21 of the 29 cases (72.4%) where the wives had a reciprocal translocation. Those with reciprocal translocations in either partner miscarried significantly more frequently than those without an abnormal karyotype. Only one infant with an unbalanced translocation was found in 34 cases of successful pregnancy following habitual abortion. CONCLUSION(S): The pregnancy prognosis with either maternal or paternal reciprocal translocations is poorer than without them. The presence of a reciprocal translocation is thus a risk factor in couples who have recurrent miscarriages.  相似文献   

4.
We report on a cytogenetic investigation of lymphocytes in 241 couples and six women with at least three abortions. We found a balanced reciprocal translocation three times (1.2% of couples) and a balanced Robertsonian translocation twice (0.8% of couples). Four numerical aberrations of the gonosomes were detected (three of them as a mosaic), and one deletion Xq- as a mosaic. The heterochromatic region of the chromosomes 1, 9 or 16 was enlarged in 12 couples (4.9%). There was no couple with a pericentric inversion of the chromosomes 1 or 9. The enlarged Y-chromosome (five males) according to our results does not play any important role for the reproduction. Five translocations and one supernumerary chromosome each in one cell only indicate an enlarged frequency of breakage events in couples with habitual abortion.  相似文献   

5.

Research question

Can next-generation sequencing (NGS) based on copy number variation sequencing (CNV-Seq) identify normal/balanced embryos in balanced reciprocal translocation carriers and what are their reproductive outcomes?

Design

One hundred couples with balanced reciprocal translocation who underwent a total of 134 preimplantation genetic testing (PGT) cycles between January 2015 and October 2017 were evaluated. Trophectoderm cells of blastocysts were biopsied for CNV-Seq-based NGS. All the balanced/normal blastocysts were vitrified and cryopreserved. Single balanced/normal blastocysts were warmed and transferred in the subsequent frozen embryo transfer (FET) cycle.

Results

During the study period, 400 blastocysts were analysed by NGS-PGT, of which 109 (27.25%) were balanced and euploid. A total of 52 blastocysts were transferred in the FET cycle. Clinical pregnancy was confirmed in 34 women (65.38%), with a miscarriage rate of 2.94%; 26 healthy term babies were born, including 24 singletons and one set of twins, while eight couples had ongoing pregnancies. Amniocentesis revealed a fetal chromosome status that was consistent with the NGS-PGT results. Female carriers had a significantly higher blastocyst rate than did the male carriers (37.01% versus 31.27%, P?=?0.04). The transferable blastocyst rate was higher in couples treated with gonadotrophin-releasing hormone (GnRH) antagonist than in those treated with GnRH agonist (38.20% versus 24.37%, P = 0.01). However, neither carrier sex nor ovarian stimulation protocol influenced the clinical pregnancy rate.

Conclusions

CNV-Seq-based NGS is an efficient and reliable PGT method for balanced reciprocal translocation.  相似文献   

6.
染色体平衡易位携带者妊娠风险及妊娠结局的研究   总被引:1,自引:1,他引:0  
目的 探讨染色体平衡易位携带者的妊娠风险及其妊娠结局.方法 194例染色体平衡易位携带者,根据平衡易位种类分成相互易位(135例)、非同源罗伯逊易位(52例)、同源罗伯逊易位(7例)3组.调查携带者生育史并随访诊断平衡易位后的妊娠情况,比较各组自然流产、先天缺陷及正常(或)平衡易位后代概率.结果 (1)194对夫妇共妊娠503例次,其中自然流产411例次(81.7%,411/503);产前诊断胎儿异常而终止妊娠16例次(3.2%,16/503);活产缺陷儿36例次(7.2%,36/503);正常(或)平衡易位后代40例次(8.0%,40/503).(2)相互易位、非同源罗伯逊易位、同源罗伯逊易位3组,活产缺陷儿比率分别为5.7%(20/350)、10.9%(14/128)、8.0%(2/25),3组间相互比较,差异有统计学意义(P<0.05);3组正常(或)平衡易位后代比率分别为6.6%(23/350)、13.3%(17/128)、0,3组间相互比较,差异有统计学意义(P<0.05);而3组自然流产及产前诊断胎儿异常终止妊娠比率比较,差异无统计学意义(P>0.05).(3)52例次先天缺陷中活产36例次(69%),经产前诊断确诊后引产16例次(31%).27例次先天缺陷获得细胞遗传学诊断,唐氏综合征发生率为59%(16/27).(4)相互易位组和非同源罗伯逊易位组共有39对夫妇得到40个正常(或)平衡易位后代,同源罗伯逊易位组无正常(或)平衡易位后代.40个正常(或)平衡易位后代中26个获得产前细胞遗传学诊断,正常核型6个(23%),平衡易位核型20个(77%).结论 染色体平衡易位携带者自然妊娠风险大,尤其同源罗伯逊易位携带者难以获得染色体正常(或)平衡易位的后代.  相似文献   

7.
Cytogenetic studies were performed in 445 couples presenting because of repetitive abortion. The authors detected a balanced translocation in 19 (4.2%) of the couples, pericentric inversions in 8 (1.8%), and polymorphisms in 52 (11.4%). The results were compared with those obtained in a series of 600 consecutive normal liveborns. Significantly higher frequencies for translocations and polymorphisms were present in couples with repetitive abortion. No sex predominance in translocation carriers was observed, and reciprocal translocations were more common (16 of 19) than the robertsonian type (3 of 19). Contrary to other reports, all of the translocations and inversions were detected among couples without previous abnormal offspring. Cytogenetic prenatal testing in 17 pregnancies from a carrier parent showed that none of the fetuses had the unbalanced karyotype, 13 carried the balanced rearrangement, and 4 had a normal karyotype. Although a risk profile can be obtained for these couples, prenatal testing must be offered to avoid anxiety and unjustified pregnancy interruptions.  相似文献   

8.
目的 观察染色体平衡易位和罗伯逊(罗氏)易位基因携带者夫妇进行植入前遗传学诊断(PGD)后的胚胎染色体遗传特征和胚胎着床、妊娠情况,探讨PGD在染色体易位基因携带者夫妇实现正常生育中的意义.方法 用荧光原位杂交(FISH)技术对36对夫妇的胚胎进行PGD,其中14例为染色体平衡易位(平衡易位组),22例为染色体罗氏易位(罗氏易位组),并对诊断结果和胚胎着床、妊娠情况进行分析.结果 36例患者共活检胚胎253个,成功诊断胚胎225个,成功率为88.9%(225/253),获得可供移植的正常或平衡的胚胎共58个.平衡易位组和罗氏易位组PGD后胚胎着床率分别为36%(5/14)和14%(6/44),临床妊娠率分别为4/9和26%(5/19).结论 PGD可有效诊断胚胎染色体平衡易位和罗氏易位,避免反复流产和不必要的非意愿性终止妊娠,并获得理想的胚胎着床率和临床妊娠率.  相似文献   

9.
Meiotic segregation patterns of 278 embryos from 41 preimplantation genetic diagnosis cycles of 34 reciprocal translocation carriers were analysed to investigate whether some characteristics of reciprocal translocation, including terminal breakpoints, acrocentric chromosome or carrier gender, are related to meiotic segregation patterns. The incidence of normal/balanced karyotypes in translocations with terminal breakpoints was significantly lower than those without terminal breakpoints (6.5% versus 14.4%, P = 0.005). The incidences of adjacent-1 (21.0% versus 29.6%), adjacent-2 (16.1% versus 11.1%) and 3:1 (41.9% versus 30.6%) segregation were not statistically significantly different in translocations with terminal breakpoints versus those without. Translocation with acrocentric chromosomes showed a significantly lower rate of 2:2 segregation (39.2% versus 60.2%, P = 0.001) and a higher rate of 3:1 segregation (43.1% versus 27.3%, P = 0.005) than those without acrocentric chromosomes. The incidence of 2:2 segregation was significantly higher in male than in female carriers (58.2% versus 45.0%, P = 0.019). This study suggested that reciprocal translocation involving terminal breakpoints resulted in a lower rate of normal/balanced karyotype in preimplantation embryos. Some characteristics of reciprocal translocation, such as terminal breakpoints, acrocentric chromosome and carrier gender, are related to the segregation patterns.  相似文献   

10.
OBJECTIVE: To investigate the incidence of chromosomal aberration in men and women in an intracytoplasmic sperm injection (ICSI) program for severe male infertility as well as in conceptuses resulting from these ICSI treatments. STUDY DESIGN: We evaluated chromosomal analysis, outcome of ICSI and the conceptuses resulting from treatment of 301 couples included in ICSI program. RESULTS: Cytogenetic evaluation demonstrated structural anomalies in 11 cases (3.6%), 9 men (2.9%) and 2 women (0.7%), all consisting of balanced chromosomal translocations. There were no significant differences in the rates of developed embryos (44.2% versus 40.1%) in couples with abnormal (n = 11) and normal (n = 290) chromosomal analysis. Embryo transfer led to a similar number of newborns (15.3% versus 12.4%) per transferred embryos, without any correlation with parents' chromosomes. In 63 fetuses conceived from couples without chromosomal abnormalities, we observed one fetus affected by Patau syndrome (47,XY, + 13). Two of four (50%) fetuses conceived by couples with male balanced chromosomal defects were carriers of the chromosomal translocation inherited from their fathers. The two fetuses resulted in the birth of two infants observed to be normal at the 12-month pediatric follow-up. CONCLUSION: The offer of this treatment to infertile couples with male factor infertility should be accompanied by proper information regarding the genetic risks of this treatment. ICSI remains a good therapeutic option for infertile patients, but prenatal diagnosis is mandatory because of the potential increased aneusomic risk for the offspring conceived.  相似文献   

11.
Cytogenetics of recurrent abortions   总被引:2,自引:0,他引:2  
Chromosome banding studies were carried out on both partners of 37 couples who had had two or more spontaneous abortions. Three patients had chromosome disorders; one was a triple-X female and the other two (one male and one female) were t(13;14) translocation carriers. Review of the literature indicates that the over-all frequency of major chromosome disorders in couples with repeated abortions is 2.6%. About three-fourths of these disorders are reciprocal and Robersonian translocations.  相似文献   

12.
OBJECTIVE: This study tests the hypothesis that IUI treatment in cases with isolated teratozoospermia (<10% normal forms using strict criteria, normal motility and normal count), results in a lower cumulative live birth rate compared to cases with normozoospermia. DESIGN: A retrospective cohort study. SETTING: An academic fertility center. PATIENT(S): Eight hundred seventy-two IUI cycles in 440 couples were analyzed. INTERVENTION(S): Couples (n = 440) were classified in three groups: normozoospermia (n = 213), isolated teratozoospermia (n = 104), and male factor infertility (n = 123). MAIN OUTCOME MEASURE(S): Live birth rate per cycle and cumulative live birth rate (CLBR). RESULT(S): The three groups were similar with regard to female age, female infertility factors, and ovarian response after hormonal stimulation. The overall CLBR after four cycles was 41.5%, and was significantly increased in the normozoospermic group (52.8%) when compared to the isolated teratozoospermia group (33.4%) and the male factor infertility group (31.4%). CONCLUSION(S): This study documents for the first time that the CLBR after four IUI cycles is significantly and similarly reduced in couples with isolated teratozoospermia as in couples with other sperm defects, when compared to couples with normozoospermia. As with couples with male factor infertility, couples with isolated teratozoospermia should be counseled about other treatment options such as IVF, as the CLBR after three IVF cycles is 70%-80% in our program.  相似文献   

13.
In order to evaluate the relation between chromosomal translocation and the outcome of pregnancy, 50 couples were examined. Subjects consisted of 35 couples that included a reciprocal translocation carrier; 13 included a Robertsonian translocation carrier and 2 included a carrier of a mosaic reciprocal translocation. The reasons for performing chromosomal examinations were mainly infertility and abnormality of neonates. The rates of miscarriages and neonatal abnormalities in prior pregnancies were significantly higher than the birth rate of morphologically normal newborns. The presence of a translocation is closely related to reproductive failure because of the chromosomal imbalance. However, prenatal chromosomal examination after the 15th gestational week in subsequent pregnancies revealed that almost half of the fetuses showed normal karyotypes and only 12.8 per cent of the fetuses showed a chromosomal imbalance. Many chromosomally imbalanced fetuses are spontaneously aborted before amniocentesis. The risk of chromosomal imbalance is relatively low in prenatal diagnosis, but partial trisomies of small rearrangements tend to be preserved.  相似文献   

14.
OBJECTIVES: To determine if the second-trimester maternal serum markers (MSM) screening for Down syndrome (DS) is efficient in DS mosaicism or structural rearrangement cases. METHOD: DS mosaic or translocation cases were reviewed from databases of routine MSM DS screening. The control group consisted of 977 trisomy 21 cases included in a series of 854 902 patients (routine screening). DS risk was calculated by combination of maternal age and MSM [alpha-fetoprotein (AFP) and human choriogonadotrophin (hCG) or free beta-hCG and/or uE3] expressed in multiples of median (MoM). Mosaic DS cases were divided into three groups, < 10%, 10-49%, and >or= 50% trisomy 21 cells. Translocation DS cases were divided into three groups, isochromosome, Robertsonian, or reciprocal translocation. Detection rate (DR) and MoMs were evaluated in each group. RESULTS: As many as 76 cases of nonstandard trisomy 21 were collected. For mosaic DS cases (n = 43) DR was 69.8% (not significantly different from the 70.8% of control group). When mosaicism was less than 10%, the DR dropped to 25%. For translocation DS cases (n = 33) DR was 75.7% (not significantly different from control group) whatever the types of translocation. CONCLUSION: In the nonstandard DS cases, second-trimester MSMs gave the same detection rate as for standard trisomy 21, except the cases with low-level mosaicism (<10%).  相似文献   

15.
ObjectiveThe presence of reciprocal and Robertsonian chromosomal rearrangement is often related to recurrent miscarriage. Using preimplantation genetic diagnosis, the abortion rate can be decreased. Cases treated at our center were reviewed.Materials and methodsA retrospective analysis for either Robertsonian or reciprocal translocations was performed on all completed cycles of preimplantation genetic diagnosis at our center since the first reported case in 2004 until the end of 2010. Day 3 embryo biopsies were carried out, and the biopsied cell was checked by fluorescent in situ hybridization using relevant informative probes. Embryos with a normal or balanced translocation karyotype were transferred on Day 4.ResultsThirty-eight preimplantation genetic diagnosis cycles involving 17 couples were completed. A total of 450 (82.6%) of the total oocytes were MII oocytes, and 158 (60.0%) of the two-pronuclei embryos were biopsied. In 41.4% of the fluorescent in situ hybridization analyses, the results were either normal or balanced. Embryos were transferred back after 21 cycles. Three babies were born from Robertsonian translocation carriers and another two from reciprocal translocation carriers. The miscarriage rate was 0%. Among the reciprocal translocation group, the live delivery rate was 8.3% per ovum pick-up cycle and 18.2% per embryo transfer cycle. Among the Robertsonian translocation group, the live delivery rate was 14.3% per ovum pick-up cycle and 20.0% per embryo transfer cycle.ConclusionThere is a trend whereby the outcome for Robertsonian translocation group carriers is better than that for reciprocal translocation group carriers. Aneuploidy screening may possibly be added in order to improve the outcome, especially for individuals with an advanced maternal age. The emergence of an array-based technology should help improve this type of analysis.  相似文献   

16.
OBJECTIVE: To determine whether seminal plasma (SP) from unexplained infertile males has different suppressive activity on antibody-dependent cellular cytotoxicity (ADCC) than SP from fertile males or SP from males of couples with known infertility factor. DESIGN: Comparative clinical/experimental study. SETTING: In vitro fertilization program in a university hospital and a hospital research laboratory. PATIENT(S): A total of 245 SP samples from 174 infertile and 16 fertile couples were compared. INTERVENTION(S): SP suppression of ADCC was measured by using human 51chromium-labeled red blood cells (RBC), sensitized with IgG-rabbit-anti-human-RBC as targets and peripheral blood lymphocytes as effector cells. MAIN OUTCOME MEASURE(S): Suppressive activity of each sample was determined by calculating 51Cr-release in the presence and absence of SP. RESULT(S): When analyzed with respect to sperm number, motility, and morphology, suppressive activities of samples with normal semen analyses (n = 142) were significantly higher (x = 37% +/- 14%) than suppressive activities of abnormal samples (n = 103; x = 32% +/- 13%). There was no strong correlation of suppressive activity to other semen parameters. Within the andrologically normal males, SP from the unexplained infertile couples (n = 15) showed significantly lower suppressive activity (x = 24% +/- 11%) compared with the SP from fertile males (n = 16; x = 35% +/- 13%) and from couples with female infertility factor (n = 65; x = 39% +/- 14%). CONCLUSION(S): Loss of suppressive activity is associated with unexplained infertility, even in male patients who previously were considered normal by traditional methods of semen analysis.  相似文献   

17.

Purpose

To compare single nucleotide polymorphism (SNP) and comparative genomic hybridization (aCGH) microarray platforms to evaluate embryos for parental translocation imbalances and aneuploidy.

Methods

A retrospective review of preimplantation genetic diagnosis and screening (PGD/PGS) results of 498 embryos from 63 couples undergoing 75 in vitro fertilization cycles due to parental carriers of a reciprocal translocation.

Results

There was no significant difference between SNP and aCGH microarrays when comparing the prevalence of embryos that were euploid with no translocation imbalance, euploidy with a parental translocation imbalance or aneuploid with or without the parental chromosome imbalance. The clinical pregnancy rates were also equivalent for SNP (60 %) versus aCGH (65 %) microarrays. Of 498 diagnosed embryos, 45 % (226/498) were chromosomally normal without translocation errors or aneuploidy, 22 % (112/498) were euploid but had a parentally derived unbalanced chromosomal segregant, 8 % (42/498) harbored both a translocation imbalance and aneuploidy and 24 % (118/498) of embryos were genetically balanced for the parental reciprocal translocation but were aneuploid for other chromosomes. The overall clinical pregnancy rate per IVF cycle following SNP or aCGH microarray analysis was 61 % and was higher if the biopsy was done on blastocysts (65 %) versus cleavage stage embryos (59 %), although not statistically significant.

Conclusions

SNP or aCGH microarray technologies demonstrate equivalent clinical findings that maximize the pregnancy potential in patients with known parental reciprocal chromosomal translocations.  相似文献   

18.
OBJECTIVE: This study reports 18 years of experience in prenatal diagnosis (PD) of cystic fibrosis (CF) in a region where CF is frequent and the uptake of PD is common (Brittany, western France). METHOD: All PDs made over the period 1989-2006 in women living in Brittany were collected. RESULTS: We recorded 268 PDs made in 1 in 4 risk couples, plus 22 PDs directly made following the sonographic finding of echogenic bowel. Most of the 268 PDs were done in couples already having CF child(ren) (n = 195, 72.8%). Close to one-fifth followed cascade screening (n = 49, 18.3%), which identified 26 new 1 in 4 risk couples among the relatives of CF patients or of carriers identified through newborn screening (NBS). The remaining PDs were mainly made in couples whose 1 in 4 risk was evidenced following the diagnosis of echogenic bowel in a previous pregnancy (n = 22, 8.2%). Although patients' life expectancy has considerably improved, in our population the great majority of couples chose pregnancy termination when PD indicated that the foetus had CF (95.9%). CONCLUSION: This study describes the distribution of PDs according to the context in which the 1 in 4 risk was discovered and highlights the real decisions of couples as regards pregnancy termination after a positive PD.  相似文献   

19.
Outcome of preimplantation genetic diagnosis of translocations   总被引:30,自引:0,他引:30  
Objective: To review 35 cases of preimplantation genetic diagnosis (PGD) of translocations with several methods, including telomeric probes.

Design: Retrospective study.

Setting: Clinical IVF laboratory.

Patient(s): Thirty-five couples with one partner carrying a chromosomal translocation.

Intervention(s): PGD of translocation after polar-body or embryo biopsy.

Main Outcome Measure(s): Pregnancy outcome.

Result(s): Several trends were observed. First, PGD can achieve a statistically significant reduction in spontaneous abortion, from 95% to 13%. Second, the chances of achieving pregnancy are correlated with 50% or more of the embryos being chromosomally normal. Third, patients with robertsonian translocations produced fewer abnormal gametes and more pregnancies than did patients with reciprocal translocations. Fourth, a new fluorescence in situ hybridization protocol for PGD of translocations, which involves applying telomeric probes, has proved adequately reliable with a 6% average error rate.

Conclusion(s): PGD of translocations achieves a statistically significant reduction in spontaneous abortion, both for polar-body and blastomere biopsy cases. Pregnancy outcome depended on the number of normal embryos available for transfer, with patients having <50% abnormal embryos achieving the most pregnancies. Because robertsonian translocations caused fewer abnormal embryos than reciprocal translocations, they also resulted in higher rates of implantation.  相似文献   


20.
Cytogenetic studies were performed on 1,180 individuals--490 couples + 200 females presenting with habitual spontaneous abortion (HSA). These revealed 24 abnormal results (2.03%)--15 were apparently balanced reciprocal translocations and 9 were Robertsonian translocations. Of 97 pregnancies among the translocation carriers, there were 10 living children and 87 pregnancy losses--a loss rate of 89.7%. There were 11 familial translocations. In 10 familial cases with a full family tree, there were 27 spontaneous abortions and 64 livebirths among the 30 adult translocation carrier relatives--a loss rate of 29.6%. This is twice the risk found in the general population but not as high as in the probands, who had 6 times the abortion rate in the general population. Mechanisms are suggested for this difference. The subsequent pregnancy history of 12 index translocation couples showed an apparently improved pregnancy outcome with 13 further fetal losses and 13 living children, over a follow-up time per patient ranging from 1-5.5 years. However, when the pregnancy losses at ascertainment were combined with postascertainment losses, the overall rate of pregnancy loss remained the same.  相似文献   

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