Zygosity and placental anatomy in 15 consecutive sets of spontaneously conceived triplets

The Prenatal Environment in Twin Studies: A Review on Chorionicity

A literature search was conducted to identify articles examining the association of chorionicity (e.g., whether twins share a single chorion and thus placenta or have separate chorions/placentas) and genetics, psychiatry/behavior, and neurological manifestations in humans twins and higher-order multiples. The main aim was to assess how frequently chorionicity has been examined in relation to heritability estimates, and to assess which phenotypes may be most sensitive to, or affected by, bias in heritability estimates because of chorionicity. Consistent with the theory that some chorionicity effects could lead to overestimation and others to underestimation of heritability, there were instances of each across the many phenotypes reviewed. However, firm conclusions should not be drawn since some of the outcomes were only examined in one or few studies and often sample sizes were small. While the evidence for bias due to chorionicity was mixed or null for many outcomes, results do, however, consistently suggest that heritability estimates are underestimated for measures of birth weight and early growth when chorionicity is not taken into account.

Impact of monozygotic twinning on multiple births resulting from in vitro fertilization in the United States, 2006-2010

OBJECTIVE

To determine the contribution of monozygotic twining to in vitro fertilization multiple births.

STUDY DESIGN

We performed a retrospective analysis of the incidence of monozygotic twining in multiple births resulting from fresh embryo transfers using 2006-2010 data from the Society for Reproductive Technology Clinic Outcome Reporting System.

RESULTS

The number of embryos transferred were fewer than the number of births in 0.5% (223/40950) of twin, 29% (659/2289) of triplet, and 64% (43/67) of quadruplet births resulting from transfer of fresh embryos from 2006 to 2010. In 2010, 37% of triplets and 100% of quadruplet births occurred when fewer than 3 and fewer than 4 embryos respectively were transferred.

CONCLUSION

Monozygotic twinning plays a key role in the development of triplet and quadruplet pregnancies achieved through in vitro fertilization.

Three-dimensional sonograph of a monochorionic diamniotic triplet pregnancy

A monochorionic diamniotic triplet pregnancy was diagnosed by sonographic scan at 9 weeks of gestation. The three embryos appeared to share the same trophoblast, with two of them sharing the same amniotic sac. The two amniotic sacs were divided by a thin membrane, with no chorionic projection within it, and each amniotic sac presented a single yolk sac. Only few cases of nontrichorionic-triamniotic triplets have been reported in the literature. Although the diagnosis was reached using the two-dimensional ultrasound, the complementary use of three-dimensional ultrasound helped in confirming the diagnosis, and in offering the couple an adequate counseling.

Paternally Derived Twinning: A Two Century Examination of Records of One Scottish Name

Paternal influence on twinning was investigated through a study of all the state and church records of Scotland for the period 1800–2000 (nine generations) in relation to one Scottish patronymic — in total 50,000 births. All recorded twins born with the chosen patronymic were identified and their whole paternal ascent and descent on the male line were charted for twins. There were established three pedigrees A, B and C manifesting clear paternal twinning hereditary transmission. Detailed familial reproduction patterns were traced for pedigree A, including phenotypic identification of twin zygosity in relation to seven same sexed pairs of twins in the pedigree and one same sexed pair out of dizygotic triplets. It is the most comprehensive description to date of such a kind of twin familial trait. The data presented show (i) the unique feature of clear direct paternal influence on twinning in three families; (ii) paternal factor(s) determination in both DZ and MZ twinning; and (iii) a definite association of twinning tendency with a partial male infertility, which corresponds to the prediction of the Infertility/Twinning Paternally Dependent syndrome hypothesis. The hypothesis of a founder effect explaining the similarity of A, B, C families and the possible localisation of the paternally dependent twinning factor on the Y-chromosome are currently under molecular investigation.

Paternal Familial Twinning: Hypothesis and Genetic/Medical Implications

The phenomenon of paternally dependent familial twinning has been known in human and animal genetics since the 1920s, but still remains without any theoretical explanation and is indeed a neglected field of inquiry. Over the last two decades investigations in reproduction biology have discovered the significant role of multiple paternally dependent errors in fertilization including androgenic triploidy and moles. We suggest the hypothesis that the fathers of twins in the relevant families carry gene variants that increase the probability of dispermy, diplospermy and male pronucleus heterochrony as well as involvement of two male pronuclei in the fertilization of two female meiotic products. Any resulting twins would be an exceptional intermediate between MZ and DZ twins — and might properly be described as “sesquizygotic” (SZ). Paternal familial twinning may also go together with infertility due to triploidy, moles and chimerism. The hypothesis: (i) places the curiosities of paternally derived twinning within the framework of current knowledge of reproductive genetics and verifiable phenomena; (ii) predicts the existence of families in which twinning is associated with reproductive abnormalities; (iii) predicts an occurrence in relevant families of the third and intermediate category of SZ twins. Families with paternal twinning may thus provide the natural selective system for the search of unusual cases of primary chimeras, the frequency of which is still unknown.

Diastolic Cardiac Pathology and Clinical Twin-Twin Transfusion Syndrome in Monochorionic/Diamniotic Twins

OBJECTIVE: to identify differences in echocardiographic profiles of monochorionic/diamniotic pregnancies with early or mild twin-twin transfusion syndrome (TTTS), compared to monochorionic/diamniotic twins affected only by discordant growth or discordant fluid. STUDY DESIGN: retrospective evaluation of sonograms and echocardiograms of twin pregnancies referred for suspected TTTS. RESULTS: 112 monochorionic/diamniotic pairs were studied. 41 did not have/develop TTTS, 61 had Stage I/II TTTS. Ten developed TTTS after initially not meeting criteria. TTTS recipients had a higher rate of venous Doppler or tricuspid inflow abnormalities than purported "recipients" in non-TTTS pregnancies (86% vs. 37%, P<0.001). TTTS recipients had shorter tricuspid inflow duration/RR intervals than non-TTTS fetuses (32+/-6% versus 37+/-4%, P<0.001). Logistic regression and recursive partitioning identified shorter tricuspid inflow duration, longer isovolumic relaxation, and ductus venosus abnormality associated with TTTS. CONCLUSION: Diastolic pathology, specifically shorter tricuspid inflow duration, may be considered a hallmark of TTTS distinguishing these pregnancies from other monochorionic/diamniotic twin complications.

Effect of selective fetoscopic laser photocoagulation therapy for twin-twin transfusion syndrome on pulmonary valve pathology in recipient twins

OBJECTIVE

To investigate the impact of selective fetoscopic laser photocoagulation (SFLP) on pre-existing pulmonary valve pathology in the recipient twin in twin-twin transfusion syndrome (TTTS).

METHODS

We evaluated preoperative echocardiograms of all pregnancies with TTTS treated with SFLP at our institution from 2001 to 2009 (n = 76). Sixteen (21%) recipients had an abnormal pulmonary valve (stenosis/dysplasia, insufficiency or functional atresia) before SFLP. Postoperative echocardiograms and medical records from these 16 recipients were reviewed. Changes in pulmonary valve structure and function, and overall cardiac function, were noted after SFLP.

RESULTS

The mean gestational age at SFLP was 21 (range, 18.7-24.3) weeks. Seven of sixteen (44%) recipients with abnormal pulmonary valve prior to SFLP survived. Six of the 16 (37.5%) recipient twins had documented absence of persistent pulmonary valve abnormalities at birth or at autopsy. Two (12.5%) of the 16 recipients (2.6% of the original cohort) had persistent pulmonary valve abnormalities at birth, requiring intervention. Systolic and diastolic function improved or normalized after SFLP in all patients undergoing longitudinal follow-up. There was a tendency for a better cardiovascular profile score (best = 10 points) at initial evaluation in pregnancies with survivors compared with those with no survivors (mean (SD): 5.6 (2.2) vs. 6.75 (1.28)), but this was not statistically significant. Severity of cardiac involvement did not predict persistence of valve pathology or survival.

CONCLUSIONS

SFLP can improve flow through the pulmonary valve of the recipient twin in TTTS, probably as a consequence of improvements in right ventricular systolic and diastolic function. However, pulmonary valve pathology may persist and require postnatal intervention.

Fetoscopic laser therapy for twin-twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) complicates approximately 1 in 5 of all monochorionic, diamniotic twin pregnancies. If of early onset and untreated, severe TTTS is associated with a dismal prognosis, with perinatal mortality rates exceeding 90%. The most controversial issue regarding the optimal treatment of TTTS has centered on the use of amniocentesis or laser until the first and only randomized trial on interventions for TTTS was published a couple of years ago, comparing laser to amnioreduction. That report confirmed that the laser group had a higher likelihood of the survival of at least one twin to 28 days of age and to 6 months of age. Infants in the laser group also had a lower incidence of cystic periventricular leukomalacia and were more likely to be free of neurologic complications at 6 months of age (52% vs. 31%, p = 0.003). Although not every case of TTTS is an eligible candidate for fetoscopic-guided laser therapy, it is recommended that obstetricians who have the chance to manage TTTS in their daily practice be familiar with the rationale behind this laser treatment for TTTS.

Perinatal outcome of spontaneously conceived triplet pregnancies in relation to chorionicity

OBJECTIVE

The purpose of this study was to determine the perinatal outcome of spontaneously conceived triplet pregnancies in relation to chorionicity.

STUDY DESIGN

In this retrospective study, maternal, neonatal, and chorionicity data were collected from 88 sets of triplet pregnancies that were delivered at >20 weeks of gestation from 3 tertiary referral centers in the United Kingdom. The data were collected between January 1986 and December 2000. There were 49 sets of trichorionic triamniotic triplet pregnancies and 39 sets of triplet pregnancies with a monochorionic pair (ie, dichorionic triamniotic triplets). The outcome of each pregnancy was assessed in relation to chorionicity.

RESULTS

The overall perinatal mortality rate was 151.5 per 1000 total births, with dichorionic triamniotic triplets having a 5.5-fold higher risk than trichorionic triamniotic gestations (odds ratio, 5.5; 95% CI, 2.5-12.2). The dichorionic triamniotic triplets have a higher risk of delivery at < 30 weeks of gestation (odds ratio, 4.6; 95% CI, 1.6-11.8; P < .05) and birth weight of < 1000 g (odds ratio, 53.6; 95% CI, 17.5-164; P < .05) than those of trichorionic triamniotic pregnancies. The neonatal morbidity in terms of respiratory distress syndrome (P < .001), anemia (P < .01), and intraventricular hemorrhage (P < .001) were higher in dichorionic triamniotic compared with trichorionic triamniotic triplets. The premature rupture of membrane (odds ratio, 7.5; 95% CI, 3.5-15.7) and twin-twin transfusion syndrome (odds ratio, 14.9; 95% CI, 6.6-4) were independent risk factors for perinatal death.

CONCLUSION

In spontaneously conceived triplets, the incidence of dichorionicity was 44%. The dichorionic triamniotic triplets have a 5.5-fold higher risk of adverse perinatal outcome predominantly because of twin-twin transfusion syndrome and premature rupture of membranes.

Prenatal diagnosis and obstetric outcomes in triplet pregnancies in relation to chorionicity

OBJECTIVE

This study describes the frequency, pregnancy complications and outcomes of non-trichorionic triplet pregnancies.

DESIGN

A retrospective observational study.

SETTING

Two tertiary level referral centres of Obstetrics and Prenatal Medicine, Germany.

POPULATION

All women booked to receive targeted ultrasound screening between January 1998 and June 2003. The mixed low and high risk population included 36,430 women with ultrasound examinations between 11 and 24 weeks of gestation. Of those with available outcome, 176 were triplet pregnancies with three viable fetuses.

METHODS

Analysis of ultrasound data and perinatal outcome in triplet gestations who had first and second trimester targeted ultrasound examination. Pregnancies with monochorionic or dichorionic placentation were identified and pregnancy outcome was compared to trichorionic triplets.

MAIN OUTCOME MEASURES

Intrauterine fetal death, fetal growth restriction (FGR), mean discordance and survival rate in non-trichorionic versus trichorionic triplets.

RESULTS

Triplets were trichorionic in 81.8% and had a monochorionic or dichorionic placentation in the remaining 18.2%. The rate of monochorionicity and dichorionicity was significantly higher after spontaneous conception than after assisted reproductive technologies (44.8%vs 12.9%, P < 0.001). In non-reduced monochorionic and dichorionic triplets compared with non-reduced trichorionic triplets, there was a higher rate of intrauterine fetal death (8.8%vs 1.5%, P < 0.01), FGR (33.3%vs 25.5%), mean discordance (20.5%vs 12.7%, P < 0.01), discordance >30% (26.3%vs 2.9%, P < 0.01) and delivery <32 weeks of gestations (47.4%vs 32.2%). There was a lower survival rate in non-trichorionic triplets (84.2%) than in trichorionic ones (91.7%).

CONCLUSION

Triplet pregnancies with a monochorionic or dichorionic placentation are at significantly higher risk of adverse pregnancy outcome compared with trichorionic pregnancies. First trimester evaluation of chorionicity is strongly emphasised.

Fetofetal transfusion syndrome in triplet pregnancies: outcome after endoscopic laser surgery

OBJECTIVE

The purpose of this study was to determine the outcome of fetofetal transfusion syndrome in triplet pregnancies after treatment with endoscopic laser ablation of communicating placental vessels.

STUDY DESIGN

Cases of severe fetofetal transfusion syndrome that occur in triplet pregnancies and that are treated with endoscopic laser ablation of placental anastomosis were identified from a prospectively collected fetal medicine database. Chorionicity was determined by sonography and classified as dichorionic or monochorionic. Perinatal outcome was obtained in all cases, and long-term follow-up was obtained in all pregnancies that resulted in at least 1 survivor.

RESULTS

During a 6-year period, 10 cases of severe fetofetal transfusion syndrome that were treated with endoscopic laser ablation were identified, of which 7 cases were dichorionic and 3 cases were monochorionic. At least 1 fetus survived in all 7 dichorionic pregnancies and in 2 of the 3 monochorionic pregnancies. In the dichorionic pregnancies, 14 of 21 fetuses (66.7%) survived, but in the monochorionic pregnancies only 2 of 9 fetuses (22.2%) survived.

CONCLUSION

Endoscopic laser ablation is feasible in triplet pregnancies that are complicated by severe fetofetal transfusion syndrome. The treatment appears to be associated with improved perinatal outcome in dichorionic, but not in monochorionic, triplets, probably because of the technical inability in achieving ablation of all the communicating vessels in monochorionic triplets.

Prenatal diagnosis of zygosity by fetal DNA analysis, a contribution to the management of multiple pregnancies. A series of 31 cases

OBJECTIVE

To evaluate the contribution of prenatal diagnosis of zygosity by fetal DNA analysis to the management of multiple pregnancies.

METHODS

Between March 1999 and March 2000, 31 same-sex multiple pregnancies, were referred to our Institute during their second trimester to have amniocentesis done. Fetal DNA variants were studied in addition to karyotype. The main indications for amniocentesis were fetal growth discordance, fetal malformations or selective pregnancy termination. Zygosity results were compared to the first-trimester ultrasound diagnosis.

RESULTS

21 out of the 31 multiple pregnancies were dizygous, and 10 out of the 31 pregnancies were monozygous. First-trimester ultrasound provided information on chorionicity only in 24 out of the 31 cases (77%). Of these 24 reports, 21 proved to be correct (87.5%). Moreover, in 2 cases among 14 pregnancies with growth discordance, DNA analysis ruled out a twin-to-twin transfusion syndrome, while ultrasound could not yield a conclusion. In 2 twin pregnancies with fetal malformations affecting one of the fetuses, DNA analysis made it possible to assess the risk for the other twin. In the 5 cases leading to selective termination, prenatal diagnosis of zygosity had a decisive value for the surviving fetus.

CONCLUSION

Fetal DNA analysis is a simple and highly useful test for prenatal diagnosis of zygosity in the management of complicated multiple pregnancies.

Some causes of genotypic and phenotypic discordance in monozygotic twin pairs

The use of the adjective "identical" rather than monozygotic leads to misunderstandings about the biology of monozygotic twinning. Most monozygotic twin pairs are not identical; there may be major discordance for birth weight, genetic disease, and congenital anomalies. These indicate that postzygotic events may lead to the formation of two or more cell clones in the inner cell mass and early embryo that actually stimulate the monozygotic twinning event. There is also evidence that there may be unequal allocation of numbers of cells to the monozygotic twins; this may have widespread implications for the cascade of developmental events during embryogenesis, formation, and vascularization of the placenta. Large-scale zygosity testing at birth could be the template for analysis of twin outcomes and their biologic causes.