Strong associations between neural tube defects (NTDs) and monozygotic (MZ) twinning have long been noted, and it has been suggested that NTD cases who do not present as MZ twins may be the survivors of MZ twinning events. We have recently shown that MZ twins carry a strong, distinctive DNA methylation signature and have developed an algorithm based on genomewide DNA methylation array data that distinguishes MZ twins from dizygotic twins and other relatives at well above chance level. We have applied this algorithm to published methylation data from five fetal tissues (placental chorionic villi, kidney, spinal cord, brain and muscle) collected from spina bifida cases (n = 22), anencephalic cases (n = 15) and controls (n = 19). We see no difference in signature between cases and controls, providing no support for a common etiological role of MZ twinning in NTDs. The strong associations therefore continue to await elucidation.

This article explicates two approaches to the basis of moral worth and status: Eva Kittay’s relational view and Jeff McMahan’s psychological personhood view. It is argued that these theories alone do not provide adequate support for the conclusions Kittay and McMahan want to draw concerning individuals whose entitlement to fundamental protections can be challenged—infants with severe cognitive disabilities and infants without the support of their families and social environments. The real justification can in each case be found in deeply held convictions regarding entities that must and entities that must not be included in the core community of moral equals. Philosophical discussions about these convictions would be more useful for the advancement of our moral thinking than vain attempts to show that the absolute truth lies on either side of the ongoing debate.

A broad range of evidence regarding the functional organization of the vertebrate brain – spanning from comparative neurology to experimental psychology and neurophysiology to clinical data – is reviewed for its bearing on conceptions of the neural organization of consciousness. A novel principle relating target selection, action selection, and motivation to one another, as a means to optimize integration for action in real time, is introduced. With its help, the principal macrosystems of the vertebrate brain can be seen to form a centralized functional design in which an upper brain stem system organized for conscious function performs a penultimate step in action control. This upper brain stem system retained a key role throughout the evolutionary process by which an expanding forebrain – culminating in the cerebral cortex of mammals – came to serve as a medium for the elaboration of conscious contents. This highly conserved upper brainstem system, which extends from the roof of the midbrain to the basal diencephalon, integrates the massively parallel and distributed information capacity of the cerebral hemispheres into the limited-capacity, sequential mode of operation required for coherent behavior. It maintains special connective relations with cortical territories implicated in attentional and conscious functions, but is not rendered nonfunctional in the absence of cortical input. This helps explain the purposive, goal-directed behavior exhibited by mammals after experimental decortication, as well as the evidence that children born without a cortex are conscious. Taken together these circumstances suggest that brainstem mechanisms are integral to the constitution of the conscious state, and that an adequate account of neural mechanisms of conscious function cannot be confined to the thalamocortical complex alone.

A case of monoamniotic monochorionic (MAMC) female twins, with one twin being anencephalic, and the co-twin being normal, is reported. Twin to twin transfusion syndrome was also noted. The reasons for anencephaly in association with monozygotic (MZ) twinning are discussed. The management of such a case is presented.

A 38-year-old woman, gravida 5, para 3, with a triplet prgnancy discordant for anencephaly, is reported. The diagnosis was made prenatally by ultrasound. Autopsy of the anencephalic member revealed small adrenal glands with absent fetal cortex, and a coincidental tetralogy of Fallot. Studies of the histocompatible lymphocyte antigens of both parents were performed and they failed to demonstrate HLA B-27. The literature on anencephaly in triplets is summarized. The association of congenital heart disease and HLA B-27 with anencephaly is discussed.

Accurate, unbiased malformation rates in twins must be obtained unselectively from population-based studies that include livebirths and stillbirths after a thorough ascertainment of cases. This type of study was conducted in Los Angeles County, California, where 28 twins with a neural tube defect (NTD) were identified. The prevalence in twins (1.6/1,000) was significantly higher than in singletons (1.1/1,000). The study then was expanded to include population-based data from the Medical Birth Registry of Norway which has a comparable overall NTD prevalence (1.0/1,000) and twinning rate (2%). The combined material shows a higher prevalence of anencephaly and encephalocele but not of spina bifida in twins compared to singletons. The male/female ratios in total twin and singleton cases were comparable (0.8), but varied by specific defect. Like-sex twin females appeared at highest risk for NTD as well as for fetal death.

This study supports theories which associate NTDs with monozygotic twins, either through developmental disruptions that cause susceptibility to environmental agents or through a common etiology. Furthermore, it suggests that twins and singletons differ in their response to etiologic factors for the development of NTDs and that the development of each type of NTD may be related to different factors.