Department of Obstetrics and Gynecology, HaEmek Medical Center, Afula and the Rappaport School of Medicine, Technion Israel Institute of Technology, Haifa, Israel
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Abstract |
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Key words: assisted reproduction/chorionicity/fetal malformation/twins conjoined/twins monozygotic
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Introduction |
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Here we report a case of conjoined twins in a triplet pregnancy conceived after ICSI. The diagnosis was made at the eighth week of gestation by early transvaginal sonography. The early diagnosis allowed selective termination of the conjoined twins. This case raises again the need for early and expert sonographic evaluation of pregnancies achieved after ICSI, as this enables accurate diagnosis and adequate counselling.
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Case report |
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At the 12th week of gestation, selective termination was done by a transabdominal approach. A 22-gauge needle was directed into the sac of the conjoined twins, and intracardiac injection of potassium chloride was performed, as described previously (Evans et al., 1990). Immediate cessation of heartbeat of the conjoined twins was seen, with normal heartbeat of the single fetus. The pregnancy is ongoing, with an apparently normal singleton fetus of 26 weeks gestation.
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Discussion |
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It has been argued that delayed ovum transport, delayed implantation and the manipulation of the egg might raise the rate of monochorionic and conjoined twins (Edwards et al., 1986; Cohen et al., 1990
). According to this assertion, both mono-amniotic and diamniotic monochorionic twins are created during hatching, when embryos may be trapped in a gap in the zona pellucida. The twins can continue to develop when the inner cell mass splits in half. This may happen either when the trophoblast splits, or when it remains intact. The latter possibility may lead to monochorionic mono-amniotic twinning, with a possibility of conjoined twins. The formation of conjoined twins probably indicates incomplete separation of the inner cell mass.
Another possibility of conjoined formation is incomplete cleavage of the embryonic disk at 1315 days after conception. Yet another possibility is formation of heteropagus, that appears like conjoined twins but results from an incomplete fusion of two embryos, which could even be dizygotic (Logrono et al., 1997). Conjoined twins had been reported after IVF and assisted hatching (Skupski et al., 1995
), but not with ICSI.
Early diagnosis of conjoined twins was previously reported, but not before the 10th week of gestation (Koontz et al., 1985; Shalev and Zuckerman, 1987
; Boulot et al., 1992
, Skupski et al., 1995
; Hubinot et al., 1997). On careful transvaginal sonography and serial scanning there appears to be an inability to separate between the anatomical parts of the fetuses. Use of colour Doppler can help in making the diagnosis, especially in revealing the exact nature of the blood circulation, as was done in the current case.
The early diagnosis of conjoined twins associated with a normal singleton permits the option of selective termination of the abnormal fetuses, and this can be offered to the women if there is certainty in the diagnosis of chorionicity. Selective termination can only be offered if the fetuses are of different chorionicity. Clinical experience with second trimester selective termination shows that the earlier the procedure is done, the lower the loss rates are. In addition, the gestational age at delivery is greater with early procedure as compared with later procedures (Berkowitz et al., 1988; Wapner et al., 1990
).
In conclusion, we report the first case of conjoined twins in a triplet pregnancy achieved after IVF and ICSI. This case was diagnosed at the eighth week of gestation, earlier than other cases reported before, emphasizing again the importance of early expert sonographic evaluation of pregnancies conceived after assisted reproduction. In this case diagnosis of different chorionicity permitted selective reduction of the abnormal pregnancy, which was done successfully at the 12th week. The pregnancy is ongoing with an apparently normal fetus of 26 weeks.
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Note added at proof |
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Notes |
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References |
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Submitted on November 22, 1999; accepted on February 28, 2000.