Vanishing Twins Research Articles

Cell-free DNA test for fetal chromosomal abnormalities in multiple pregnancies.

This study aimed to report the screening performance of cell-free DNA (cfDNA) testing for chromosomal abnormalities in twins, triplets, and vanishing twin pregnancies. Data were obtained from pregnant women with a multiple pregnancy or a vanishing twin pregnancy at ≥10 weeks' gestation who requested self-financed cfDNA testing between May 2015 and December 2021. Those that had positive screening results had diagnostic confirmatory procedures after counseling and consent. The performance of screening of the cfDNA test was determined by calculating confirmation rate and combined false-positive rate (cFPR). Data from 292 women were included after exclusion of those lost to follow-up, with no-result on cfDNA testing, or had reductions. Of the 292 pregnancies, 10 (3.4%) were triplets, including no cases of trisomy 21 and trisomy 18; 249 (85.3%) were twins, including 3 cases of trisomy 21 and no cases of trisomy 18 and 13; and 33 (11.3%) were vanishing twins, including 3 cases of trisomy 21 and 1 case of trisomy 18. The median (IQR) maternal age was 34 years (31-37). For triplet pregnancies, the initial no-result rate was 10.3% (95% confidence interval [CI] 3.6-26.4), all with results after redraw. For twin pregnancies, the initial no-result rate was 12.9% (95% CI 9.6-17.0), and the no-result rate after redraw was 1.6% (95% CI 0.7-3.6). For vanishing twins, there were no cases with no-result. All triplets had low-risk cfDNA results. The confirmation rate for trisomy 21 was 100% with a FPR at 0% due to the small number of positive cases for twins. For vanishing twins, one high-risk case for trisomy 21 and the only high-risk case for trisomy 18 were confirmed with a cFPR of 8.3% (n = 2/24; 95% CI 2.3-25.9). cfDNA testing in twin pregnancies has sufficient screening performance for trisomy 21 but the number of affected cases for other conditions is limited to draw any meaningful conclusion. The use of cfDNA testing in triplet pregnancies and vanishing twins remains an area for further research.

Non-invasive prenatal testing (NIPT) in twin pregnancies affected by early single fetal demise: A systematic review of NIPT and vanishing twins.

The screening performance of non-invasive prenatal testing (NIPT) in vanishing twin (VT) pregnancies is relatively unknown. To close this knowledge gap, we conducted a systematic review of the available literature. Studies describing the test performance of NIPT for trisomy 21, 18, 13, sex chromosomes and additional findings in pregnancies with a VT were retrieved from a literature search with a publication date until October 4, 2022. The methodological quality of the studies was assessed with the quality assessment tool for diagnostic accuracy studies-2 (QUADAS-2). The screen positive rate of the pooled data and the pooled positive predictive value (PPV) were calculated using a random effects model. Seven studies, with cohort sizes ranging from 5 to 767, were included. The screen positive rate of the pooled data for trisomy 21 was 35/1592 (2.2%), with a PPV of 20% (confirmation in 7/35 cases [95% CI 9.8%-36%]). For trisomy 18, the screen positive rate was 13/1592 (0.91%) and the pooled PPV 25% [95% CI 1.3%-90%]. The screen positive rate for trisomy 13 was 7/1592 (0.44%) and confirmed in 0/7 cases (pooled PPV 0% [95% CI 0%-100%]). The screen positive rate for additional findings was 23/767 (2.9%), of which none could be confirmed. No discordant negative results were reported. There is insufficient data to fully evaluate NIPT performance in pregnancies with a VT. However, existing studies suggest that NIPT can successfully detect common autosomal aneuploidies in pregnancies affected by a VT but with a higher false positive rate. Further studies are needed to determine the optimal timing of NIPT in VT pregnancies.

Vanishing Twins Syndrome (VTS) - A case report

Vanishing twin’s syndrome refers to the death of one of the co-twin fetus(es) during the early antenatal period. The cause of vanishing twins is unknown, and most cases occur with In-Vitro Fertilization (IVF) conception. Transvaginal Ultrasonography helps to detect lost twins during the early trimester. The complications that may arise among neonates born to women with a known history of vanishing twin syndrome are low birth weight and low Apgar score at birth.

Should Vanishing Twin Pregnancies Be Systematically Excluded From Cell-Free Fetal DNA Testing?

(Abstracted from Prenat Diagn 2021;41:1241–1248) The goal of this study was to gain a better understanding of the impact of vanishing twins (VTs) on the incidence of discrepant cfDNA testing results. To do so, the researchers analyzed a series of cases of patients with VT to determine the extent to which this compromised cfDNA testing results.

Non-invasive prenatal testing in the management of twin pregnancies.

Twin pregnancies are common and associated with pregnancy complications and adverse outcomes. Prenatal clinical management is intensive and has been hampered by inferior screening and less acceptable invasive testing. For aneuploidy screening, meta‐analyses show that non‐invasive prenatal testing (NIPT) through analysis of cell‐free DNA (cf‐DNA) is superior to serum and ultrasound‐based tests. The positive predictive value for NIPT is driven strongly by the discriminatory power of the assay and only secondarily by the prior risk. Uncertainties in a priori risks for aneuploidies in twin pregnancies are therefore of lesser importance with NIPT. Additional information on zygosity can be obtained using NIPT. Establishing zygosity can be helpful when chorionicity was not reliably established early in pregnancy or where the there is a concern for one versus two affected fetuses. In dizygotic twin pregnancies, individual fetal fractions can be measured to ensure that both values are satisfactory. Vanishing twins can be identified by NIPT. Although clinical utility of routinely detecting vanishing twins has not yet been demonstrated, there are individual cases where cf‐DNA analysis could be helpful in explaining unusual clinical or laboratory observations. We conclude that cf‐DNA analysis and ultrasound have synergistic roles in the management of multiple gestational pregnancies.

When Is Non-Invasive Prenatal Testing Reliable in Pregnancies with Vanishing Twin? - A Review of Case Reports

Background: Fetal demise can complicate aneuploidy screening in a multi fetal pregnancy. The cell-free DNA (CF-DNA) from a non-viable conception may lead to be discordant with the viable fetuses. The Aim of study was to review the waiting period, follow-on single fetal demise in a twin gestation before performing NIPT. Materials and Methods: In this review articlewe searched through online database with keywords: ((NIPT) (non-invasive prenatal screening testing) (cell-free DNA) (vanishing twin) (co-twin demise)), including: CINAHL, Cochrane, Database of Abstracts of Reviews of Effects (DARE), PubMed, and Medical Library. For English literature between 2011 and 2020 which included duration between vanishing twin or reduction and NIPT false results. Results: 201 studies across the eight scientific web sites were detected. 178 excluded for duplication or being irrelevant. 29 studies were fully read. 4 case series, met the criteria for systematic review. The finding suggested the NIPT screening test can be falsely-positive several weeks after vanishing twins although live fetus is normal. Therefore, duration in which placenta can release CF-DNA of vanished twin is unknown. In addition, several weeks after reduction the fetal CF-DNA increases and then decreases, thus CF-DNA analyzing in multi-fetal pregnancies with reduction can be challenging as well. Conclusion: In pregnancies with vanishing twin or reduction, evaluating NIPT results is more complex than single fetal pregnancy. According to studies, after a fetal demise, the cytotrophoblast continues to release to the CF-DNA in the maternal circulation for a variable time, which may cause a false-positive result if the demised twin is aneuploidy.

Vanishing Twins Conceived Through Fresh In Vitro Fertilization: Obstetric Outcomes and Placental Pathology.

To characterize the obstetric outcomes and placental pathology in live births arising from vanishing twin pregnancies compared with nonreduced in vitro fertilization (IVF) pregnancies. This is a retrospective cohort study of live births resulting from fresh embryo transfers after IVF cycles with autologous oocytes from 2004 through 2017 at a large academic fertility center. Clinical information and pathology reports were reviewed. Placental diagnoses were coded using established nosology by expert placental pathologists. Analysis of variance, Kruskal-Wallis, Pearson's χ, and Fisher exact tests were used, as appropriate, to compare pathology categories between pregnancy outcomes. Mixed effects logistic regression models were generated to reveal the association between pregnancy outcome and placenta pathology, controlling for pregnancies arising in the same woman and various suspected confounders. Of 905 fresh autologous IVF cycles with placental pathology available for review, we identified 73 vanishing twin pregnancies (8.1%), 556 singleton pregnancies (61.4%), and 276 twin pregnancies (30.5%). Vanishing twin syndrome was not associated with preterm delivery, route of delivery, growth restriction or other obstetric outcomes as compared with IVF singleton pregnancies. However, vanishing twin syndrome pregnancies showed distinctive placental pathologies including an increased rate of small placentas (less than the 10th percentile by weight), with more anatomical abnormalities than IVF singleton pregnancies (odds ratio 1.73, 95% CI 0.94-3.19; adjusted odds ratio 2.15, 95% CI 1.08-4.28). The frequency of placental vascular and inflammatory pathologies associated with IVF vanishing twin syndrome pregnancies were similar to that of IVF singleton pregnancies. Loss of a twin after 8 weeks of gestation was not associated with greater risks of placental pathologies. In vitro fertilization pregnancies affected by vanishing twin syndrome did not have significant differences in obstetric or perinatal outcomes as compared with twin or singleton gestations. However, early twin loss was potentially associated with differences in placental development associated with a higher rate of small placentas and other anatomic pathologies.

Perinatal and Peripartum Outcomes in Vanishing Twin Pregnancies Achieved by In Vitro Fertilization.

To compare perinatal and peripartum outcomes of vanishing twin gestations with singleton and dichorionic twin gestations in pregnancies conceived by in vitro fertilization. We conducted a retrospective cohort study of vanishing twin pregnancies after fresh and cryopreserved autologous in vitro fertilization cycles performed at our institution from 2007 to 2015. Singleton, dichorionic twin, and dichorionic twin pregnancies with spontaneous reduction to one by 14 weeks of gestation (vanishing twins) were included. Analysis was restricted to patients with a live birth delivery at our institution at or beyond 24 weeks of gestation. The primary outcomes were gestational age and birth weight at delivery; secondary outcomes included peripartum morbidities. A subanalysis further differentiated the vanishing twin pregnancies between those in which demise of the twin occurred before compared with after identification of fetal cardiac activity. Logistic regression models were used to estimate the adjusted odds ratio (OR) with a 95% CI of outcomes. There were 1,189 pregnancies that met inclusion criteria (798 singleton, 291 twin, and 100 vanishing twin). The mean gestational age at birth and birth weights were 38.6±2.3 weeks of gestation and 3,207±644 g in singleton pregnancies, 35.5±2.7 weeks of gestation and 2,539±610 g in twin pregnancies, and 38.5±1.8 weeks of gestation and 3,175±599 g in vanishing twin pregnancies. When compared with twins, those with a vanishing twin had lower odds of preterm delivery (OR 0.13, 95% CI 0.07-0.23; adjusted OR 0.12, 95% CI 0.07-0.22) and small-for-gestational-age birth weight (OR 0.24, 95% CI 0.13-0.45; adjusted OR 0.14, 95% CI 0.07-0.28). In pregnancies conceived by in vitro fertilization that progress to at least 24 weeks of gestation, vanishing twin and singleton pregnancies had similar perinatal and peripartum outcomes. Both were significantly better than twin pregnancies.

Vanishing twin syndrome among ART singletons and pregnancy outcomes.

STUDY QUESTIONAmong babies born by ART, do singleton survivors of a vanishing twin have lower birth weight than other singletons?SUMMARY ANSWERVanishing twin syndrome (VTS) was associated with lower birth weight among ART singletons; a sibship analysis indicated that the association was not confounded by maternal characteristics that remain stable between deliveries.WHAT IS KNOWN ALREADYPrevious studies indicate that ART singletons with VTS have increased risk of adverse pregnancy outcomes, compared with other ART singletons. The potential contribution of unmeasured maternal background characteristics has been unclear.STUDY DESIGN, SIZE AND DURATIONThis was a Norwegian population-based registry study, including 17 368 mothers with 20 410 ART singleton deliveries between January 1984 and December 2013.PARTICIPANTS/MATERIALS, SETTING, METHODSThe study population included 17 291 ART singletons without VTS, 638 ART singletons with VTS and 2418 ART singletons with uncertain vanishing twin status. We estimated differences in birth weight and gestational age comparing ART singletons with VTS first to all ART singletons without VTS, and subsequently to their ART siblings without VTS, using random- and fixed-effects linear regression, respectively. The corresponding comparisons for the associations with preterm birth and small for gestational age (SGA) were conducted using random-and fixed-effects logistic regression. The sibling analysis of preterm birth included 587 discordant siblings, while the sibling analysis of SGA included 674 discordant siblings.MAIN RESULTS AND THE ROLE OF CHANCEART singletons with VTS had lower birth weight when compared to all ART singletons without VTS, with an adjusted mean difference (95% CI) of −116 g (−165, −67). When we compared ART singletons with VTS to their ART singletons sibling without VTS, the adjusted mean difference was −112 g (−209, −15). ART singletons with VTS also had increased risk of being born SGA, with an adjusted odds ratio (OR) (95% CI) of 1.48 (1.07, 2.03) compared to all ART singletons without VTS, and 2.79 (1.12, 6.91) in the sibship analyses. ART singletons with VTS were also more likely to be born preterm, although this difference did not reach statistical significance.LIMITATIONS REASONS FOR CAUTIONWe did not have information on maternal socio-economic status, but this factor is accounted for in the sibship analyses. We also had no information on whether fresh or frozen embryos were replaced.WIDER IMPLICATIONS OF THE FINDINGSThe reduction in birth weight and increased risk of SGA in ART singletons with VTS may suggest the presence of harmful intrauterine factors with long-term health impact. While vanishing twins are not routinely observed in naturally conceived pregnancies, loss of a twin is potentially a risk factor for the surviving foetus in any pregnancy. This could be further explored in large samples of naturally conceived pregnancies with the necessary information.STUDY FUNDING/COMPETING INTEREST(S)The authors of this study are supported in part by the UK Medical Research Council, US National Institute of Environmental Health Sciences and the Norwegian Research Council. The authors have no conflicts of interest.TRIAL REGISTRATION NUMBERN/A.

Detection of triploid, molar, and vanishing twin pregnancies by a single-nucleotide polymorphism–based noninvasive prenatal test

We sought to determine the ability of single-nucleotide polymorphism-based noninvasive prenatal testing (NIPT) to identify triploid, unrecognized twin, and vanishing twin pregnancies. The study included 30,795 consecutive reported clinical cases received for NIPT for fetal whole-chromosome aneuploidies; known multiple gestations were excluded. Cell-free DNA was isolated from maternal blood samples, amplified via 19,488-plex polymerase chain reaction, and sequenced. Sequencing results were analyzed to determine fetal chromosome copy number and to identify the presence of additional fetal haplotypes. Additional fetal haplotypes, indicative of fetal triploidy, vanishing twin, or undetected twin pregnancy, were identified in 130 (0.42%) cases. Clinical confirmation (karyotype for singleton pregnancies, ultrasound for multifetal pregnancies) was available for 58.5% (76/130) of cases. Of the 76 cases with confirmation, 42.1% were vanishing twin, 48.7% were viable twin, 5.3% were diandric triploids, and 3.9% were nontriploid pregnancies that lacked evidence of co-twin demise. One pregnancy had other indications suggesting triploidy but lacked karyotype confirmation. Of the 5 vanishing twin cases with a known date of demise, 100% of losses occurred in the first trimester; up to 8 weeks elapsed between loss and detection by NIPT. This single-nucleotide polymorphism-based NIPT successfully identified vanished twin, previously unrecognized twin, and triploid pregnancies. As vanishing twins are more likely to be aneuploid, and undetected residual cell-free DNA could bias NIPT results, the ability of this method to identify additional fetal haplotypes is expected to result in fewer false-positive calls and prevent incorrect fetal sex calls.

Pitfalls in noninvasive fetal RhD and sex determination due to a vanishing twin

What's already known about this topic? Risk of misdiagnosis in NIPT carried out by cfDNA analysis in presence of vanishing twins. Importance of ultrasound monitoring since early gestational age in case of NIPT.What does this study add? Precise monitoring of the cfDNA released from a vanishing twin in a noninvasive fetal RhD and sex determination. Exhaustive follow‐up of pregnancy since delivery.

Early beta-human chorionic gonadotropin trends in vanishing twin pregnancies

To describe the early β-hCG trends in vanishing twins compared with normally progressing singleton and twin pregnancies. Retrospective cohort study. University-based infertility clinic. Women undergoing fresh IVF/intracytoplasmic sperm injection (ICSI) cycles between 1998 and 2010. Early β-hCG level increase in vanished twin pregnancies was compared with the level increase in normally progressing singleton and twin pregnancies. Two-day percent increase in β-hCG level. Pregnancies with vanishing twins demonstrated a significantly lower mean 2-day percent increase in β-hCG level than singletons and twins (114.3% vs. 128.8% and 125.4%, respectively). Vanishing twins arresting at earlier developmental stages demonstrated significantly further reduced β-hCG level increases. Infrequently, all groups had β-hCG level increases less than previously established clinical thresholds that led to a live birth. Early β-hCG level increases are slower in vanishing twins than in singleton and twin pregnancies, with the slowest increases seen when the spontaneous fetal losses occur at earlier developmental stages. All increases, however, are within clinically accepted normal limits. Therefore, abnormal β-hCG level increases should not be attributed to a vanishing twin. Of note, an abnormal β-hCG level trend--even an initial decrease--does not preclude live birth, even in a singleton pregnancy.

The influence of the type of embryo culture medium on neonatal birthweight after single embryo transfer in IVF

Does the type of medium used to culture fresh and frozen-thawed embryos influence neonatal birthweight after single embryo transfer (SET) in IVF? A comparison of two commercially available culture media showed no significant influence on mean birthweight and mean birthweight adjusted for gestational age, gender and parity (z-scores) of singletons born after a fresh or frozen-thawed SET. Furthermore, we show that embryo freezing and thawing cycles may lead to a significantly higher mean birthweight. Animal studies have shown that culture media constituents are responsible for changes in birthweight of offspring. In human IVF, there is still little knowledge of the effect of medium type on birthweight. Until now, only a small number of commercially available culture media have been investigated (Vitrolife, Cook(®) Medical and IVF online medium). Our study adds new information: it has a larger population of singleton births compared with the previously published studies, it includes outcomes of other media types (HTF and Sage(®)), not previously analysed, and it includes data on frozen-thawed SETs. This study was a retrospective analysis of birthweights of singleton newborns after fresh (Day 3) or frozen-thawed (Day 5) SET cycles, using embryos cultured in either of two different types of commercially available culture media, between 2008 and 2011. Before January 2009, a single-step culture medium was used: human tubal fluid (HTF) with 4 mg/ml human serum albumin. From January 2009 onwards, a commercially available sequential medium was introduced: Sage(®), Quinn's advantage protein plus medium. Singletons born after a fresh SET (99 embryos cultured in HTF and 259 in Sage(®)) and singletons born after a frozen-thawed SET (32 embryos cultured in HTF only, 41 in HTF and Sage(®) and 86 in Sage(®) only) were analysed. Only patients using autologous gametes without the use of a gestational carrier were considered. Also excluded were (vanishing) twins, triplets, babies with congenital or chromosomal abnormalities and babies born before 22 weeks of gestation. Analysis of 358 singletons born after a fresh SET and 159 singletons born after a frozen-thawed SET showed no significant difference between the HTF and Sage(®) groups in terms of birthweight. Gestational age, parity and gender of the baby were significantly related to birthweight in multiple linear regression analyses, and other possible confounding factors included maternal age, BMI and smoking, the number of blastomeres in the transferred embryo and the type of culture medium. Maternal age, BMI and smoking, gestational age at birth, gender of the baby and the percentage of firstborns did not differ significantly between the HTF and Sage(®) groups; however, among the fresh embryos, those cultured in Sage(®) had significantly more blastomeres at the time of embryo transfer compared with the embryos cultured in HTF. Birthweights adjusted for gestational age and gender or gestational age and parity (z-scores) were not significantly different between the HTF and Sage(®) groups for fresh or frozen-thawed SETs. Mean birthweight, as well as the mean birthweight among firstborns and the mean birthweights adjusted for gestational age and gender or parity (z-scores) were significantly higher in the cryopreservation group compared with the fresh embryo transfer group. Our study is limited by its retrospective design and only two commercially available types of culture media were tested. More research is necessary to investigate the potential influence of culture media on gene expression. Although our data do not indicate the major influences of the HTF and Sage(®) culture media on birthweight, our results cannot be extrapolated to other culture media types. Furthermore, there remains a potential influence of embryo culture environment on epigenetic variation not represented by birthweight differences but by more subtle features.

The impact of vanishing fetuses on the outcome of ICSI pregnancies

Vanishing fetal twins occurred in 9% (264 out of 2,829) intracytoplasmic sperm injection pregnancies and are associated with a lower fetal loss rate in the first trimester. The live birth rate was higher in pregnancies associated with vanishing fetuses.

Deleterious consequences of vanishing twins (VT) in IVF/ICSI pregnancies: a large study from a single institution

Spontaneous reduction of twins is not uncommon and is estimated to occur in 15–30% of all twin pregnancies. In multicentered studies, the VT syndrome has been associated with decreased birthweight and an increase in preterm deliveries. In this study, we analyzed a large cohort of patients from a single institution to determine if there was an association between VT's and delivery outcome.

Consequences of Vanishing Twins in IVF/ICSI Pregnancies

In Denmark, 4% of children at present are born by in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). Singleton IVF/ICSI infants are relatively likely to be preterm and have low birth weight. Spontaneous reductions may increase morbidity in singleton IVF infants. Previous work indicates that “vanishing” twins is not the only factor in adverse outcomes. The authors analyzed data on women with ongoing IVF/ICSI pregnancies that were detected by transvaginal sonography in gestational week 8. The goals were to determine the frequency of spontaneous reductions in IVF/ICSI twin pregnancies and to compare morbidity in survivors of a vanishing cotwin with both singletons and born twins. Included were 642 survivors of a vanishing cotwin, 5237 singletons from single gestations, and 3678 twins from twin gestations. Approximately 10% of all IVF singletons born resulted from a twin gestation in early pregnancy. On multiple logistic regression analysis, adjusting for maternal age, parity, and ICSI, the odds ratio (OR) for birth weight below 2500 g in singleton survivors of a vanishing twin was 11.7 (95% confidence interval [CI], 1.2–2.2), and for birth weight below 1500 g, it was 2.1 (95% CI, 1.3–3.6), compared with singletons resulting from single gestations. Corresponding figures were obtained for preterm births. The increased risk was almost entirely the result of reductions occurring after 8 weeks gestation. No increase in the risk of neurologic sequelae was found in survivors of a vanishing cotwin compared with singletons. The OR for cerebral palsy, however, was 1.9 (95% CI, 0.7–5.2). The later in pregnancy that spontaneous reduction began, the higher the risk of neurologic sequelae. The adjusted OR of child death was 3.6 (95% CI, 1.7–7.6) in survivors compared with the singleton cohort. These findings suggest that outcomes for IVF/ICSI survivors of a vanishing cotwin have poorer outcomes than singletons from single gestations. Because approximately 10% of IVF/ICSI singletons result from a vanishing twin pregnancy, this may explain the relatively adverse outcomes observed in IVF/ICSI singleton infants. These considerations favor elective single embryo transfer, which will reduce the high risk of twins and may also lessen the risk of spontaneous reduction and the poor outcomes associated with it.

Consequences of vanishing twins in IVF/ICSI pregnancies

Spontaneous reductions are a possible cause of the increased morbidity in IVF singletons. The aim of this study was to assess incidence rates of spontaneous reductions in IVF/ICSI twin pregnancies and to compare short- and long-term morbidity in survivors of a vanishing co-twin with singletons and born twins. We identified 642 survivors of a vanishing co-twin, 5237 singletons from single gestations and 3678 twins from twin gestations. All children originated from pregnancies detected by transvaginal sonography in gestational week 8. By cross-linkage with the national registries the main endpoints were prematurity, birth weight, neurological sequelae and mortality. Of all IVF singletons born, 10.4% originated from a twin gestation in early pregnancy. Multiple logistic regression analyses adjusted for maternal age, parity and ICSI treatment showed for birth weight <2500 g an odds ratio (OR) of 1.7 [95% confidence interval (CI) 1.2-2.2] and for birth weight <1500 g OR 2.1 (95% CI 1.3-3.6) in singleton survivors of a vanishing twin versus singletons from single gestations; corresponding figures were seen for preterm birth. This increased risk was almost entirely due to reductions that occurred at >8 weeks gestation. We found no excess risk of neurological sequelae in survivors of a vanishing co-twin versus the singleton cohort; however, OR of cerebral palsy was 1.9 (95% CI 0.7-5.2). Furthermore, we observed a correlation between onset of spontaneous reduction, i.e. the later in pregnancy the higher the risk of neurological sequelae (r = -0.09; P = 0.02). Adjusted OR of child death within the follow-up period was 3.6 (95% CI 1.7-7.6) in the survivor versus the singleton cohort. One in 10 IVF singletons originates from a twin gestation. Spontaneous reductions that occur at >8 weeks gestation are one of the causes for the higher risk of adverse obstetric outcome in IVF singletons.

Vanishing twin due to an apparent gnomic imbalance

The disappearance of one or more gestational rings on repeated ultrasonic examination during the 1 st trimester have led to the vanishing twin phenomenon. In recent years, the concept of vanishing twins has gained much attention during genetic amniocentesis. A couple was initially referred to us because of a high incidence of fetal loss. They later conceived with a twin pregnancy, however, one of the twins was lost at 7 weeks of gestation while the other one is a normal, 46,XX female. The couple experienced three more successive fetal losses and was referred for cytogenetic evaluation. Cytogenetic findings with GTG-and FISH- techniques revealed a balanced translation between chromosomes 9 and 11 in the father i.e. 46,XY,t(9;11)(p22;q22). ish 46,XY,t(9;11)(p22;q22)(wcp9+;wcp11+) while the mother is cytogenetically normal, 46XX. It is obvious that the vanished twin was cytogenetical abnormal with an unbalanced karyotype. The couple is religious and do not wish to go through an amniocentesis but want to have at least 10 more children. All options were explained to them. Their Rabbi suggested that they are only allowed a non-invasive procedure that must occur prior to five weeks of pregnancy. At present, the technology allowing enough maternal cells of fetal origin to be captured at such an early stage has not been perfected. The genetic and social aspects of vanishing twins is presented.