Breast disorders cause great anxiety for women especially when they occur in pregnancy because breast cancer is the most common cause of cancer related deaths in women. Majority of the disorders are Benign Breast Diseases (BBD) with various degrees of associated breast cancer risks. With increasing breast cancer awareness in Nigeria, we sought to determine the prevalence and characteristics of breast disorders among a cohort of pregnant women.A longitudinal study of 1248 pregnant women recruited in their first trimester- till 26 weeks gestational age consecutively from selected antenatal clinics (ANCs), in Ibadan, Southwest Nigeria. A pretested interviewer- administered questionnaire was used to collect information at recruitment. Clinical Breast Examination (CBE) using MammaCare® technique was performed at recruitment and follow up visits at third trimester, six weeks postpartum and six months postpartum. Women with breast disorders were referred for Breast Ultrasound Scan (BUS) and those with Breast Imaging Reporting and Data System (BIRADS) ≥4 had ultrasound guided biopsy. Statistical analysis was performed using Stata version 14.Mean age of participants was 29.7 ± 5.2 years and mean gestational age at recruitment was 20.4 ± 4.4 weeks. Seventy-two participants (5.8%) had a past history of BBD and 345 (27.6%) were primigravidae. Overall, breast disorder was detected among 223 (17.9%) participants and 149 (11.9%) had it detected at baseline. Findings from the CBE showed that 208 (69.6%) of 299 breast disorders signs found were palpable lumps or thickenings in the breast, 28 (9.4%) were persistent pain, and 63 (21.1%) were abscesses, infection and mastitis. Twenty out of 127 (15.7%) participants who had BUS performed were classified as BIRADS ≥3. Lesions found by BUS were reactive lymph nodes (42.5%), prominent ducts (27.1%), fibroadenoma (9.6%), breast cysts (3.8%) and fibrocystic changes (2.5%). No malignant pathology was found on ultrasound guided biopsy.Breast lump is a major breast disorder among pregnant women attending antenatal clinics in Ibadan. Routine clinical breast examination and follow up of pregnant women found with breast disorders could facilitate early detection of pregnancy associated breast cancer in low resource settings.