OBJECTIVE: To compare pregnancy outcome in sickle cell-haemoglobin C (SC) disease with that in homozygous sickle cell (SS) disease and age-matched controls with a normal haemoglobin (AA) genotype. DESIGN: A cohort study followed from birth. SETTING: Sickle Cell Clinic, University Hospital and other Jamaican hospitals. POPULATION: Ninety-five pregnancies in 43 patients with SC disease, 94 pregnancies in 52 patients with SS disease and 157 pregnancies in 68 controls. METHODS: Systematic review of all pregnancies occurring in sample population. Kaplan-Meier analysis for interval to first pregnancy, and the t test, chi2 test or Fisher’s exact test as appropriate; correction was made for multiple testing and multiple linear regression was used for analysis of determinants of birthweight. MAIN OUTCOME MEASURES: Age at menarche, interval to first pregnancy, outcome of pregnancy, maternal complications and possible predictors of low birthweight. RESULTS: Menarche was marginally delayed in SC disease compared with AA controls (median age 13.7 vs 13.0 years, P= 0.02) but age at first pregnancy was similar (median age 22.5 vs 20.1 years, P= 0.32). Pregnancy outcome in SC disease did not differ from AA controls but compared with SS disease there were marginally fewer miscarriages, more live deliveries and greater birthweight. The prevalence of pregnancy-induced hypertension, pre-eclampsia, antepartum or postpartum haemorrhage in SC disease did not differ from AA controls but the prevalence of sickle-related complications was similar to SS disease. CONCLUSIONS: Contrary to some claims, pregnancy outcome in SC disease is generally benign compared with SS disease.