ABSTRACT Development of the posterior neural tube (PNT) in human embryos is a complicated process which involves both primary and secondary neurulation. Normal development of the human PNT should be understood to elucidate the pathogenesis of spinal neural tube defects, but there have been some discrepancies among previous reports. We examined histologically 20 human embryos around the stage of the posterior neuropore closure and found that the developing PNT can be divided into three parts: (1) the most rostral region which corresponds to the posterior part of the primary neural tube; (2) the junctional region of the primary and secondary neural tubes; and (3) the caudal region which emerges from the neural cord. In the junctional region, the axially condensed mesenchyme (AM) intervened between the neural plate/tube and the notochord. The AM appeared to be incorporated into the most ventral part of the primary neural tube, and no cavity was observed in the AM. Interestingly, we found three cases of human embryos with lumbosacral myeloschisis in which the open primary neural tube and the closed secondary neural tube overlapped dorso-ventrally. The open and closed neural tubes appeared to be part of the primary and the AM-derived secondary neural tubes, respectively. Thus, these findings suggest that in embryos with lumbosacral myeloschisis, the AM may not be incorporated into the ventral part of the primary neural tube but aberrantly differentiate into the secondary neural tube containing cavities, leading to dorso-ventral overlapping of the primary and secondary neural tubes. These findings suggest that the AM in human embryos plays some role in normal and abnormal development of the human posterior neural tube.
ABSTRACT Research over the past 50 years has consistently documented that cell death is an integral part of both normal development and the etiology of birth defects; however, the significance of this cell death has been, until recently, unclear. Research published during the past 15 years has now shown that programmed cell death (PCD) and teratogen-induced cell death are genetically controlled processes (apoptosis) that play important roles in both normal and abnormal development. Therefore, the purpose of this review is to highlight what is known about PCD and teratogen-induced cell death and their relationships to the mechanisms of apoptosis and abnormal development.
ABSTRACT The embryonic period is characterized by organogenesis and accompanying dynamic changes in external features. The measurement of human embryos has been limited to whole body dimensions, such as crown-rump length. More detailed measurements would add quantitative information about these characteristic events and provide a better understanding of normal and abnormal embryonic development. In the present study, we defined axes, landmarks, and measurements for human embryos, and measured 250 externally normal human embryos at Carnegie stages 14–23 (6.5–29.3 mm in crown-rump length, approximately 5–8 weeks of estimated ovulation age) that were fixed in Bouin's solution and preserved in 10% formalin solution. The axes, landmarks, and measurements defined for human embryos are corresponding to those in human and primate fetuses. The whole body, head, face, and extremities were measured using a scale attached to a dissecting microscope. Axial length, head height plus ear-shoulder length plus trunk height, was designated as a new measurement of the whole body, which is comparable with crown-rump length. Approximate standards of these measurements were obtained. The ratios of some measurements to trunk height and between the different parts were also obtained, and several different developmental patterns were recognized. The reproducibility of each measurement was evaluated by measuring 50 specimens three times each at intervals of one or two months. As a pilot study for the application of the proposed measurements, 84 human embryos with external anomalies, including holoprosencephaly, anomalies of extremities, and pharyngeal arch anomalies, were measured using the same method, and a few tendencies characteristic to holoprosencephaly were noticed.
ABSTRACT Epileptic women do not withdraw antiepileptic drug (AED) therapy during pregnancy, therefore, exposure to AED during preimplantation stages might result in considerable embryonic concentrations endangering development. Neither clinical nor experimental research has addressed this important issue adequately. Vigabatrin (VGB), a second generation AED, is both effective and well tolerated as an add-on therapy in epilepsy with partial seizures. However, there is little data on the possible reproductive toxicity of this widely used drug. The objective of the present study was to evaluate the effects of VGB on pregnancy and pregnancy outcome in an experimental model. VGB was administered in single doses of 450 mg/kg intraperitoneally (IP) to groups of mice on one of gestation days (GD) 1, 3, or 5. The treated animals consumed moderately reduced amounts of food and water on the day of treatment, so the controls were saline-injected and food and water-restricted to match the amounts consumed by the experimental animals. All animals were killed on GD 18. VGB treatment did not interfere with implantation, nor did it cause significant embryo resorption. However, it caused significant reduction in fetal bodyweight and increased frequency of growth restricted fetuses which weighed two standard deviations (SD) less than the mean of the controls. The VGB group fetuses also had retarded development of the skeletal system in terms of delay in maturity of the suproccipital bone development, cervical and coccygeal vertebral hypoplasia, and poor ossification of the bones of the fore and hind paws. Another major finding was the increased incidence of minor malformations, such as the presence of cervical ribs and sternal anomalies. The results of this study show that VGB administered at preimplantation stages of development causes intrauterine growth restriction (IUGR) and augments minor malformation rates in mice. Future studies must address the mechanisms of VGB-induced IUGR and minor malformations.
ABSTRACT The aim of the investigation was to describe the risk of selected types of birth defects among older siblings of infants and fetuses with specific birth defects. Using data from a population-based birth defects registry in Hawaii for deliveries during 1986–2000, the precurrence risk (risk among older siblings) for any major birth defect, birth defects of the same organ system, and same specific birth defect were calculated for nine major organ systems and 54 specific birth defects. The precurrence risk of any major birth defect (3.5%) was substantially less than the risk of any major birth defect among the entire population (4.7%). The precurrence risk of a birth defect of the same organ system was significantly higher than the reference rate for six (67%) of the major organ systems and eight (15%) of the specific birth defects. The precurrence risk of the same birth defect was substantially elevated for 15 (28%) of the specific birth defects. Precurrence risk of any major birth defect was not elevated, but tended to be lower than expected. However, for several categories, precurrence risk of birth defects of the same organ system or the same specific birth defect was substantially elevated.
ABSTRACT The occurrence of double aneuploidy in the one person is a relatively rare phenomenon. A 5-year-old child, the second-born of non-consanguineous parents, possessed an extra X chromosome in addition to trisomy 21. The proband's parents and his brother showed normal karyotype. The phenotypic characteristics of the child have been discussed in light of the published reports on double aneuploidies of XXY and trisomy 21.
ABSTRACT This case report highlights the need for detailed consideration of a patient's entire medical history before complex surgical management. This is a complex case of congenital urogenital anomaly that had obstetric complications. Our patient had a pelvic hematoma following a home birth, which was treated with pelvic artery embolization. We are fortunate to have local expertise in pelvic artery embolization and demonstrate excellent multidisciplinary management of a complex case.
ABSTRACT A 19-year-old woman was scanned at 10+6 weeks gestation by 2D-3D ultrasound. The fetus had a crown-rump length of 40.9 mm, with the cephalic pole occupied by a single cystic cavity measuring 10.6 × 7.7 × 6.8 mm and severe hypotelorism associated with mid-facial hypoplasia. 3D ultrasound confirmed the malformations seen on the 2D scan and enabled the visualization of a proboscis and a low-set right ear. Fetal karyotyping was performed by chorionic villus sampling. Due to major fetal malformations of the fetus, the patient opted for termination of pregnancy. First trimester sonographic diagnosis of holoprosencephaly relies on bilateral visualization of choroid plexuses in what has been called the ‘butterfly’ sign. Differential diagnosis between holoprosencephaly and hydranencephaly may be difficult in the first trimester of pregnancy. However, midline structures such as falx cerebri, interhemispheric fissure and third ventricle are present in hydranencephaly and are absent in alobar holoprosencephaly, and thalami are never fused in hydranencephaly. 3D ultrasound has demonstrated an increased definition of anatomical abnormalities of malformations, compared with 2D ultrasound, and has proven to be crucial in the decision-making process of parents and in later prenatal counseling, especially in this case where necroscopy examination was refused by the parents. Images obtained by 3D ultrasound gave detailed insight into this ventral midline anomaly, depicting much of the disordered prosencephalic development.