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Epidemiology of Neural Tube Defects
Published in Michele Kiely, Reproductive and Perinatal Epidemiology, 2019
Two mechanisms whereby NTDs arise from fusion of twin conceptuses have been proposed: NTDs in one of a pair of twins arise from fusion of two members of a set of triplets and, in singletons, from fusion of twin conceptuses.33 This was thought to explain the complete lack of concordance found in the study of Yen and MacMahon34 but, since then, some concordant pairs have been identified (Table 13). Quadruplet conception, or etiological heterogeneity, has to be invoked to account for the concordant cases.MZ twins concordant for NTDs fuse to form conjoined twins, whereas DZ twins fuse to form one survivor, the tissue from the co-twin forming a teratoma or an area of skin with different chromosomal sex.210,211 Only indirect supporting evidence is available such as case reports of anencephalus with incomplete twinning,212,213 the association of intraspinal teratoma with spina bifida and the analogous phenomenon of fetus in fetu.214
The pregnant woman, childbirth, and multiple pregnancies
Published in Frank J. Dye, Human Life Before Birth, 2019
If the separation is not complete, a condition of conjoined twins (“Siamese twins”) results. The conjoining may be trivial and easily corrected surgically, or it may be a profound joining that cannot be safely severed by the surgeon's knife. There might even be a situation known as fetus in fetu, in which one twin is rather normal except that a tiny second twin is attached as an appendage. The story of the original “Siamese twins,” Chang and Eng, is fascinating reading (Figure 11.3).
Conjoined twins
Published in Prem Puri, Newborn Surgery, 2017
Juan A. Tovar, Leopoldo Martinez
Asymmetric conjoined twins represent, in general, surgical challenges that are not unlike other ones met in this specialty. The acardius acephalus parasitic twin is inviable and dies upon clamping the umbilical cord of the host (autositus) twin. The fetus in fetu is treated as a tumor, and heteropagus asymmetric parasitic twins are removed with attention to preserving as much tissue as possible in order to respect the organs and allow wall reconstruction of the host.
Twin Fetus-in-Fetu: The Story of an Encaged Twin
Published in Fetal and Pediatric Pathology, 2023
Md Ali Osama, Priti Chatterjee, Amit Gupta
Fetus in fetu is a result of an abnormal embryogenesis in which a vertebrated heteropagus fetus (the parasite) is located in the body of its normally developed twin. This terminology was first used by Lewis, and was subsequently described by Meckel as a malformed vertebrate fetus with identifiable organogenesis, found inside the body of its twin partner [3]. The essential feature that entails for FIF is the presence of well-developed fetal organs macroscopically, vertebral columns and limbs. Variable degree of organogenesis have led to the development of lungs, kidneys, liver, intestine, and genitalia of the parasitic twin in the published case reports. The existence of a distinct spinal column connotates that the fetus has passed through a primary stage of gastrulation which involves formation of neural tube, metamerization, and symmetrical development around the vertebral axis. The diagnosis of FIF is difficult when the mass does not contain an obvious vertebral axis. The FIF is attached to the host twin via a body stalk containing a single main feeding artery and vein, representing umbilical vessels. There is absence of an independent circulatory system and a true placenta for the twin fetus. The growth of the parasitic twin may be hindered either due to the vascular dominance of the host twin or an inherent defect in the parasitic twin.
Diagnostic Dilemma of an Umbilical Mass in a Newborn Infant - a Twin or a Tumor?
Published in Fetal and Pediatric Pathology, 2021
Thangaraj Abiramalatha, Rekha Balasubramanian, Febe Renjitha Suman, Prakash Agarwal, Umamaheswari Balakrishnan, Prakash Amboiram
In fetus-in-fetu, the parasitic twin is present within the abdominal cavity of autosite [5,6]. The parasitic mass usually has a segmented longitudinal axis, vertebral column and grossly recognizable anatomic features. It is covered with skin, enclosed within an amniotic sac and is attached to the autosite by a vascular pedicle. Our case is not a fetus-in-fetu since the parasitic twin was not enclosed within the abdominal cavity of the autosite.