Article 1

A Hypothesis for the Aetiology of Spastic Cerebral Palsy -- The Vanishing Twin
Pharoah, P. D.

The aetiology of spastic cerebral palsy (CP), in the majority of cases, is not known but the general consensus is that cerebral impairment occurs prepartum. In monochorionic twin pregnancies, death of one twin late in gestation is recognised as being an important risk factor for the surviving cotwin to have CP. It has been suggested that a a significant proportion of singletons with spastic CP may be the result of death of a cotwin in the second half of gestation. In this paper it is hypothesised that spastic CP unknown aetiology is the result of the death of a monochorionic cotwin and that the death of the cotwin may impair the neurological development of the survivor throughout gestation. If so, vanishing-twin syndrome, which is now a recognised phenomenon revealed by ultrasound examination in early pregnancy, is important in the aetiology of spastic CP.







Article 2

The "Vanishing Twin": Ultrasonographic Assessment of Fetal Disappearance in the First Trimester
Landy, M.D., H., Weiner, M.D., S., Corson, M.D., S.

Review of the sonographic findings of 1000 pregnancies with viable gestations in the first trimester revealed a minimum incidence of twinning of 3.29%. Of these, 21.9% demonstrated the "vanishing twin" phenomenon, often with associated bleeding, but with a good prognosis for the remaining fetus. Ovulation induction did not appear to alter these data. The sonographic criteria for "vanishing twin" are discussed. The incidence of multiple gestation is 3.29% to 5.39%, higher than previously believed. (Am J Obset Gynecol 1986;155:14-9.)









Article 3

Human Chorionic Gonadotropin Rise in the Normal and Vanishing Twins Pregnancies
Kelly, M.D., M. P.

Results:  A vanishing twin occurred in one third of the twin pregnancies. Forty-six percent of these losses occurred after fetal heart activity had been established.
Conclusions:  Vanishing twin phenomenon occurred in a large proportion of twin pregnancies in this infertility population. Fetal heart activity was not a reliable predictor of continuing fetal viability in early twin gestation. Vanishing twin conceptions were characterized by a slower rate of rise of hCG than normally progressing twin pregnancies.
Fertil Steril 56:211, 1991

The twin resorption rate of 320.5% in this study is consistent with previous reports.

References: Levis, S: Ultrasonic assessment of the high rate of human multiple pregnancy in the first trimester. J Clin Ultrasound 4:3, 1976.








Article 4

The Vanishing Twin: Morphologic and Cytogenetic Evaluation of an Ultrasonographic Phenomenon
Rudnicki, M., Vejerslev, L.O., Junge, Jette

Abstract. Twin pregnancy was observed by ultrasonographic examination in the 6th week of gestation. After singleton term delivery a thickening of the membranes opposite to the main placenta showed degenerated chorionic villi embedded between one layer of amnion and chorion; no fetal parts were observed. Villus cells from both placentas were mainly deploid; 2 of 30 were tetraploid. Marker analysis was consistent with duplication of a normal conception diploid chromosome complement as the mechanism for tetraploidy. Postconceptional nondisjunction leading to tetraploidy in one twin conceptus may explain demise in early pregnancy. Tetraploidy observed by chorionic villus biopsy most be confirmed by amniocentesis before interruption of the pregnancy is considered. Gynecol Obstet Invest 1991;31:141-145

At birth the only remnants of a vanishing twin may be fibrous thickening of part of the membranes. The possible difference between chromosome constitution i fetal and extrafetal tissue has important implications for prenatal diagnosis. Further studies of cytogenetic constitution related to histology could increase our understanding of the initial events, the frequency of mono- and dizygotic twinning and the implications of chromosome aberrations in the "vanishing twin".





Article 5

Clinical and Morphologic Aspects of the Vanishing Twin Phenomenon
Jauniaux, M.D., E., Elkazen, M.D., N., Leroy, M.D., PhD., F., Wilkin, M.D., PhD., P., Rodesch, M.D., PhD, F., Hustin, M.D., PhD., J.

The pathologic findings in placentas from ten multiple gestation complicated by the so-called vanishing twin phenomenon were studied to confirm the ultrasonographic evidence. Five pregnancies resulted from in vitro fertilization and embryo transfer, and five conceptions were spontaneous. The pregnancies were studied by repeat ultrasound examinations between five and 12 weeks' gestation. First-trimester bleeding was the only clinical sign of this phenomenon was found in five cases. Morphologically, the lesions were characterized by well-delineated plaques of perivillous fibrin deposition, associated in one case with embryonic remnants. This focal degenerative change of the placental mass, which also exists in about 25% of placentas from uncomplicated term pregnancies, may be the only clue to the disappearance of one conceptus. (Obstet Gynecol 72:577, 1988) October,1988

The vanishing twin phenomenon has spurred the curiosity of many investigators since the advent of ultrasound in the last decade. There is no doubt that some twins or fetuses of higher multiple pregnancies die in utero before delivery. Ultrasound studies have demonstrated that the vanishing phenomenon occurs during the second half of the first trimester or early in the second trimester. However, morphologic evidence of tissue remaining from the disappearing twin has rarely been reported.

The chance of carrying a multiple pregnancy to term, when complicated by early embryonic disappearance, is good, and that the prognosis for the surviving twin is better in early cases than in cases of second- and third-trimester fetal death.






Article 6

First-Trimester Bleeding and the Vanishing Twin: A Report of Three Cases
Saidi, M.D., M. H.

Ultrasonic examination of early pregnancies can lead to the discovery of vanishing twins. The main reason for such an evaluation is bleeding in the first trimester. A vanishing twin need not adversely affect the development of a coexisting singleton pregnancy. Therapeutic dilation and curettage for threatened or inevitable abortion should be avoided until a sonogram rules out the presence of a potentially surviving twin.

The phenomenon of the vanishing twin is not widely recognized as a cause of first-trimester bleeding. Approximately 5% of patients who presented because of first-trimester bleeding carried this diagnosis. Significant numbers of patients with multiple pregnancy will experience first-trimester bleeding, but in those with a vanishing twin the incidence of early-pregnancy bleeding may be as high as 90%. Journal of Reproductive Medicine Volume 33, Number10/October 1988






Article 7

The Vanishing Twin: pathologic Confirmation of an Ultrasonographic Phenomenon
Sulak, M.D., L., Dodson, M.D., M.

Although the phenomenon of the "vanishing twin" has been noted repeatedly through the use of ultrasound, no confirmatory histologic evidence has been presented previously. This has raised questions concerning the validity of the vanishing twin syndrome. A triplet intrauterine pregnancy was diagnosed ultrasonographically four weeks after in vitro fertilization, but only a single fetus and placenta were delivered at term. Careful examination of the placenta revealed at term. Careful examination of the placenta revealed histologic evidence of the vanished twin. This evidence consisted of a chorion-lined sac containing amorphous material, surrounded by degenerated chorionic villi juxtaposed against a normal amniochorionice membrane. (Obstet Gynecol 68:811, 1986)

Landy et al reviewed nine sonographic studies that documented a vanishing twin frequency of between 53 and 78% in multiple pregnancies diagnosed sonographically during the first trimester.

Presented here is pathologic evidence of a vanished twin, and criteria for the diagnosis of similar cases is suggested.

Levi reported that 71% of twin gestation diagnosed sonographically before the tenth week of were indeed singletons when delivered.

Robinson and Caines observed 30 women diagnosed sonographically as having twin gestation in the first trimester. Fourteen patients ultimately delivered twins, for a disappearance rate of 16 in 30 (53.3%).

Loss of one twin during early gestation has a much higher incidence (53-78%) than the reported abortion rate of 10-15% for a singleton pregnancy or, by comparison, an expected 20-30% chance of at least one or both twins being aborted, if such events were independent. This suggests that local influences or competition between twins may result in an exceptionally high vanished twin rate during early pregnancy. In triplets and quadruplets, the effect of early fetal competition between twins may be even more intense. In reporting 300 early pregnancies evaluated by means of ultrasound noted 21 twins, one triplet, and one quadruplet. Only three pairs of twins survived to term (85.6% loss of the second twin), whereas the triplet pregnancy evolved into a normal twin gestation, and the quadruplet pregnancy reported here also evolved into a singleton gestation, and the quadruplet pregnancy evolved into a singleton gestation. The triplet pregnancy reported here also evolved into a pregnancy diagnosed by means of ultrasound that evolved into a twin gestation. These very high resorption rates, which cannot be explained on the basis of the expected abortion rate, again suggest intense fetal competition for space, nutrition, or other factors during early gestation, with frequent loss or resorption of the other twin(s). Another explanation would be an exceptionally high incidence of genetically or embryologically abnormal embryos in multiple gestation, with loss of one twin during the early gestational period.








Article 8

The Vanishing Twin: An Explanation for Discordance Between Chorionic Villus Karyotype and Fetal Phenotype
Reddy, M.B., K.S., Petersen, S.E., M.B., Antonarakis, S.E., Blakemore, K.J.

The proportion of multiple gestation sustaining a very early loss is as high as 63 and 71 per cent according to two other sonographic series (Levi, 1975: Schneider et al., 1979). Employing the 48 per cent figure, 'vanishing twins' might be expected in 1.6-2.6 per cent of pregnancies continuing as singletons.

Many women may experience a short interval of vaginal spotting or bleeding associated with the loss of a twin early in pregnancy. Very early sonography, at 6-8 weeks of gestation, would identify the majority of these as echolucencies suggestive of a degenerating twin sac or sometimes more clearly as an embryonic demise. Prenatal Diagnosis, Volume 11,679-684(1991)








Article 9

A Normal 46,XX Infant with a 46,/69, Placenta: A Major Contribution to the Placenta is from a Resorbed Twin
Callen, D.F., Fernandez, H., Hull, Y.J., Svigos, J.M., Chambers, H.M., Sutherland, G.R.

A predominantly triploid 69,XXY placenta was found associated with a normal 46,XX infant. Therefore, a triploid placenta is apparently capable of supporting normal fetal development. The chromosome and pathological results support th conclusion that the triploid placenta originates from a 'vanishing twin' pregnancy. This case is unusual in that persistence of the placenta from the vanished twin has virtually replaced most of the normal placenta. Prenatal Diagnosis, Volume 11,437-442(1991)