Human Reproduction, Vol. 15, No. 2, 474-475,
February 2000
© 2000 European Society of Human Reproduction and Embryology
Acardiac twin pregnancy: associated with trisomy 2: Case report
Department of Gynecology and Obstetrics, Division of Prenatal Diagnosis and Therapy, University of Vienna, 1090 Vienna, Austria
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Abstract |
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Acardiac anomaly is a rare complication of multiple pregnancies. Arterial-to-arterial vascular anastomoses between twins, in the presence of a fused placenta, develop in the first trimester. Consequently the pump twin provides the acardius with blood. The second case of acardiac twin pregnancy with cytogenetic analysis of the acardiac showing the karyotype 47,XX,+2 is presented. Literature of acardiac twin pregnancies with different cytogenetic results and cases with trisomy 2 are reviewed, and a hypothesis of genesis is put forward.
Key words: acardius/trisomy 2/twin pregnancy/twin reversed arterial perfusion
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Introduction |
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The development of the acardiac anomaly is a rare complication of monozygotic multiple pregnancies. It was first described in the sixteenth century (Benedetti, 1533
and occurs in ~1% of monozygotic twin pregnancies and in one out of 35 000 deliveries (James, 1977). The most widely accepted theory on the pathogenesis of acardius is the occurrence of a twin reversed arterial perfusion sequence (TRAP) (Haring et al., 1993). The second case of acardiac twin pregnancy in which a cytogenetic investigation of the acardiac fetus resulting from trisomy 2 is presented.
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Case report |
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A 26 year old primigravida was referred to our division at 22 weeks of gestation. Prenatal ultrasonographic screening showed one fetus with inconspicuous anatomy and structure. There were no signs of decompensation and biometry corresponded to 20 weeks gestation. Additionally a gestational sac of 45 mm diameter, with a fetal pole of 29 mm diameter without cardiac beat were present. Maternal medication during pregnancy consisted in 900 mg oxcarbazepin daily against epileptic fits; the pregnancy was uneventful.
Labour was induced by prostaglandin 10 days after the due date. Because of fetal distress, Caesarean section was performed at 42 weeks gestation. A healthy girl with Apgar score 9/10/10 was delivered. The umbilical cord had three vessels, the birth weight was 2860 g, the length was 49 cm and the infant had no signs of decompensation. The acardiac twin with a single umbilical artery was delivered in a separate amniotic sac, together with the monochorionic placenta.
The acardiac twin is presented in Figure 1; the skeleton deformation on X-ray is presented in Figure 2. Cytogenetic analysis by fetal skin culture of the acardiac twin showed the karyotype to be 47,XX,+2. Cytogenetic analysis by lymphocyte culture of the healthy co-twin showed 46,XX, of the 26 year old mother 46,XX, and of the 34 year old father 46,XY.
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Discussion |
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Literature about cytogenetic investigation of acardiac twins is limited. In several acardiac monsters, investigators found karyotypes that were different from those of the co-twin (Table I
) (Benirschke and Kaufmann, 1995) and there is one reported case of an acardiac twin with trisomy 2 in a triplet in-vitro fertilization (IVF) pregnancy (Chaliha et al., 1999). In contrast, the pregnancy presented here was conceived without assisted reproduction; nevertheless the incidence of monochorionic twin pregnancies after IVF and the risk for TRAP in pregnancies of higher order is greater.
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The aetiology of cytogenetic discordancy in TRAP twins is unclear. Polar body fertilization was described in an acardiac twin pregnancy (Bieber et al., 1981
), but zygosity testing excluded polar body fertilization as a likely cause of TRAP (Fisk et al., 1996). In our opinion there are two further possible hypotheses: (i) different karyotypes in monozygotic twins may result from postzygotic non-disjunction if it occurred after, or around the time of, embryonic splitting. However, one would have expected that late non-disjunction would lead to mosaicism, and early splitting would most probably lead to dichorionicity; (ii) monochorionic twin pregnancies in humans are either monozygotic (attributed to late splitting at least 4 days after fertilization, or dizygotic which is attributed to fusion of two separate placentae). The development of acardiac fetuses in one of a pair of dizygotic twins in certain animal species who share anastomoses after fusion of two separate placentae has been described (Benirschke, 1995), and there could be an equivalent pathomechanism in humans.
Chromosomal analysis of the acardiac twin presented here showed trisomy 2. Only a few abortions in the late first trimester have been reported and no case of trisomy 2 in which the fetus survived into the second trimester have been described (Kleinebrecht and Geisler, 1975). The principal perinatal problems associated with acardiac twinning such as pump-twin congestive heart failure, maternal hydramnios, and preterm delivery (Moore et al., 1990) did not occur in our case, probably because of comparatively minor weight of the acardius. To evaluate the impact of aneuploidy in acardiac twin pregnancies, cytogenetic investigations should be carried out routinely.
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1 To whom correspondence should be addressed at: P.O.Box 41, A–1097 Vienna, Austria
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References |
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Submitted on August 5, 1999; accepted on October 22, 1999.
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