One hundred and twenty women recruited from attenders at the antenatal clinic of the Obstetrics Department of a general hospital were asked to complete ad hoc questionnaires during pregnancy; they were then interviewed by psychiatrists using a structured diagnostic interview, the Schedule for Affective Disorders and Schizophrenia (SADS). Nineteen (16 %) women were identified as having an onset of an affective disorder during the period of pregnancy, mainly (68 %) during the first trimester. As compared with the women without any such onset (controls), the women with pregnancy-related affective disorder (PRAD) were characterized by (1) it being their first pregnancy or first delivery with past termination of pregnancy, (2) early loss of either parent by death, (3) high Eysenck Personality Questionnaire (EPQ) Neuroticism (N) and Psychoticism (P) scores, (4) living in a flat with either a plan to stay there after the forthcoming childbirth or an expectation that their accommodation would be crowded, and (5) negative response to the news of the pregnancy by the husband with low intimacy. The effects of these factors were additive since the probability of developing a PRAD episode was highly correlated with the number of factors reported.