BackgroundPreterm birth is the leading cause of infant morbidity and mortality globally. Infants who are born preterm suffer long term health consequences. There only few studies done on risk factors for prematurity in Tanzania. This study aimed to determine the risk factors for preterm birth among women who delivered preterm babies at Bugando Medical Centre in Mwanza, Tanzania. MethodsA matched case-control study was conducted at the Bugando Medical Centre from May to June 2015. A total of 50 women with preterm birth (cases) were matched with 50 women who had term births (controls). Cases were matched with controls by date of delivery. We excluded mothers with multiple gestations and those who were sick and unsuitable for the interview. A structured questionnaire was used to collected relevant information from all participants. Data analysis was performed using SPSS version 20.0. Odds ratios with 95% confidence interval were estimated in a multivariate regression model to determine factors associated with preterm delivery. ResultsThe preterm birth rate was 13%. Numerous factors were associated with increased odds of preterm birth. These include regular menstrual cycle (OR 5.8; 95% CI: 2.3-14.9); planned abortion (OR 3.8; 95% CI: 1.1-13.1); use of fertility treatment during the index pregnancy (OR 7.0; 95% CI: 1.9-27.3); inadequate ANC visits (OR 9.0; 95% CI: 3.2-28.3); antepartum haemorrhage (OR 3.1 95% CI: 1.1-8.8); uterine pain during the index pregnancy (OR 5.0 95% CI: 1.7-14.4); urinary tract infections during the current pregnancy (OR 5.7 95% CI: 2.1-14.9); abnormal vaginal discharge in the current pregnancy (OR 7.4; 95% CI:2.6-20.7) and use of traditional medicine (OR 5.6; 95% CI: 2.1-14.9). The association between preterm birth and previous miscarriage, chronic hypertension, physical abuse during pregnancy and previous preterm birth disappeared after controlling for other covariates. ConclusionsThe rate of preterm birth in our study corresponds with the national prevalence. A number of maternal factors increase women likelihood of having preterm delivery. Early identification of these factors during prenatal care and provide with appropriate care may reduce the risk of preterm birth.