Research Letter
First-trimester diagnosis of recurrent omphalocele associated with fetal
trisomy 18 but without parental mosaicism
Chih-Ping Chen a,b,c,d,e,f,*, Liang-Kai Wang a, Schu-Rern Chern b, Yu-Ling Kuo g, Yen-Ni Chen a, Chen-Wen Pan a and Wayseen Wang b,h
a Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan b Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan
c Department of Biotechnology, Asia University, Taichung, Taiwan
d School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan e Institute of Clinical and Community Health Nursing, National Yang-Ming University, Taipei, Taiwan f Department of Obstetrics and Gynecology, School of Medicine, National Yang-Ming University, Taipei,
Taiwan
g Department of Obstetrics and Gynecology, Kaohsiung Medical University Hospital, Kaohsiung Medical
University, Kaohsiung, Taiwan
h Department of Bioengineering, Tatung University, Taipei, Taiwan
* Correspondence to: Chih-Ping Chen, MD
Department of Obstetrics and Gynecology, Mackay Memorial Hospital 92, Section 2, Chung-Shan North Road, Taipei, Taiwan
Tel: +886-2-25433535; Fax: +886-2-25433642, +886-2-25232448 E-mail: [email protected]
A 32-year-old, primigravid woman was diagnosed to have fetal omphalocele by prenatal ultrasound at 12 weeks of gestation (Fig. 1A). Her husband was 36 years old. The parents were normal, and there was no family history of congenital malformations. The woman did not receive any assisted reproductive technology during this pregnancy. The pregnancy was subsequently terminated, and a fetus was delivered with isolated omphalocele. Postnatal cytogenetic analysis of chorionic villi obtained by placental sampling revealed a karyotype of 47,XY,+18. Polymorphic DNA marker analysis by quantitative fluorescent polymerase chain reaction (QF-PCR) assays showed a maternal origin of the extra chromosome 18. The woman was pregnant again one year later, and prenatal ultrasound at 12 weeks of gestation revealed recurrent isolated omphalocele (Fig. 1B). Amniocentesis was performed at 13 weeks of gestation, which revealed a karyotype of 47,XX,+18. The mother had a karyotype of 46,XX. The father had a karyotype of 46,XY. The pregnancy was terminated at 14 weeks of gestation, and a 28-g fetus was delivered with isolated omphalocele. QF-PCR analysis of the placental tissue revealed a maternal origin of the extra chromosome 18.
With the advent of prenatal ultrasound, the early detection of fetal omphalocele is feasible [1]. The peculiar aspect of the present case is the occurrence of recurrent isolated omphalocele associated with trisomy 18 of maternal origin in two consecutive pregnancies. Omphalocele is not uncommon in fetuses associated with trisomy 18. Snijders et al [2] found that omphalocele occurred in 31% of the fetuses (n = 137) associated with trisomy 18. Chen [3] found that trisomy 18 occurred in 24.1% (277/1148) of the fetuses with prenatally detected omphalocele. In a review of the first-trimester sonographic findings in trisomy 18, Sepulveda et al [4] found that the common structural anomalies detected by ultrasound are omphalocele (21%), abnormal posturing of the hands (6%), megacystis (4%) and abnormal four-chamber view of the heart (4%). The present case was associated with a maternal origin of the extra chromosome 18 in two consecutive pregnancies. Various studies have shown that in cases with trisomy 18, only 9% are of paternal origin, and 91% are of maternal origin of which 60% are caused by a meiosis II error, 30% are caused by a meiosis I error, and about 8% are caused by a mitotic error [5-7]. Chen et al
[8] reported that 9.7% of the cases with trisomy 18 are the results of paternal non-disjunction, whereas 90.3% of the cases with trisomy 18 are the results of maternal non-disjunction. The live birth prevalence of trisomy 18 is estimated to be 1:6,000 [9,10]. The recurrence risk of a family with a child with complete trisomy 18 is usually reported to be 1% [11]. Prenatal diagnosis of recurrent trisomy 18 in a family should alert the presence of parental mosaicism for trisomy 18 [12-16]. Less than 5% of the cases with trisomy 18 are mosaic, and the individuals with mosaic trisomy 18 can be apparently phenotypically normal adults [13-16]. Therefore, prenatal detection of recurrent trisomy 18 should include a cytogenetic investigation of the parents to exclude parental mosaic trisomy 18. Our case represents a very rare occurrence of recurrent trisomy 18 with the same structural abnormality without a parental mosaicism.
Acknowledgements
This work was supported by research grants NSC-101-2314-B-195-011-MY3 and MOST 103-2314-B-195-010 from the Ministry of Science and Technology and MMH-E-104-04 from Mackay Memorial Hospital, Taipei, Taiwan.
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Figure Legend
Fig. 1. (A) Prenatal ultrasound at 12 weeks of gestation at the first pregnancy shows an isolated omphalocele (arrow). (B) Prenatal ultrasound at 12 weeks of gestation at the second pregnancy shows an isolated omphalocele (arrow).
