DURING THE last decade, there has been a resurgence of interest in the relationship between prenatal and perinatal adversity and schizophrenia. Driving this interest is the notion that a physically traumatic event happening either in utero or during delivery disrupts the normal development of the central nervous system (CNS). In time, the altered CNS causes the individual to develop schizophrenia. This has become known as the neurodevelopmental hypothesis.1-4 While a number of in utero events have been linked with schizophrenia, the one that has received the most scrutiny is maternal influenza during the second trimester of pregnancy. In this issue of the Archives, two other toxic events that occur during pregnancy and that may also lead to schizophrenia are described: RhD incompatibility5 and severe nutritional deficiencies.' In their most severe form, the disorders produced by these events lead to death or to clearly observable neurological abnormalities; however, it