From a series of 180 admissions to a Mother-Baby Unit 45 patients with diagnoses of schizophrenia were identified. Demographic data together with clinical information were noted, and each file was rated using the OPCRIT programme. Two mutually exclusive groups were derived from OPCRIT, a 'narrow group' (n = 16), corresponding to subjects satisfying Feighner's criteria for schizophrenia, and a 'broad group' (n = 21), corresponding to those meeting ICD10 but not Feighner criteria. In addition to significant differences in age on admission, employment, home circumstances, ethnicity and age of onset of illness, there was a marked contrast between broad and narrow groups in course of illness post partum. 43% of the broad group experienced an acute illness episode after delivery compared with none of the narrow group, a contrast not attributable to differences in clinical state or treatment during pregnancy. These data suggests that childbirth may exert a differential effect on the course of illness in severe and more benign forms of schizophrenia, and that more severe schizophrenic illnesses may not be influenced by the changes associated with childbirth, such as the fall in oestrogen levels.