Objective. To study mode of birth, perinatal health and death in children born to mothers with intellectual disability (ID) in Sweden. Design. Population-based register study. Setting. National registers; the National Patient Register linked to the Medical Birth Register. Sample. Children of first-time mothers with ID (n = 326; classified in the International Classification of Diseases 8–10) were identified and compared with 340 624 children of first-time mothers without ID or any other psychiatric diagnosis between 1999 and 2007. Methods. Population-based data were extracted from the National Patient Register and the Medical Birth Register. Main outcome measures. Mode of birth, preterm birth, small for gestational age, Apgar score, stillbirth and perinatal death. Results. Children born to mothers with ID were more often stillborn (1.2 vs. 0.3%) or died perinatally (1.8 vs. 0.4%) than children born to mothers without ID. They had a higher proportion of cesarean section birth (24.5 vs. 17.7%) and preterm birth (12.2 vs. 6.1%), were small for gestational age (8.4 vs. 3.1%) and had lower Apgar scores (<7 points at five minutes; 3.7 vs 1.5%) compared with children born to mothers without ID. Logistic regression adjusted for maternal characteristics confirmed an increased risk of small for gestational age (odds ratio 2.25), stillbirth (odds ratio 4.53) and perinatal death (odds ratio 4.25) in children born to mothers with ID. Conclusions. Unborn and newborn children of mothers with ID should be considered a risk group, and their mothers may need better individual-based care and support.