OBJECTIVES: To prospectively assess the impact of pelvic pain, vaginal bleeding and nausea and vomiting in the first trimester of pregnancy on long-term pregnancy outcomes. METHODS: Prospective observational cohort study at Queen Charlotte's & Chelsea Hospital, London, UK, from March 2014-2016. Consecutive women with confirmed intrauterine pregnancies between 5-14 weeks gestation were recruited. Serial ultrasound scans were performed in the first trimester. Participants completed validated symptom scores for vaginal bleeding, pelvic pain, and nausea and vomiting. The key symptom of interest was any pelvic pain and/or vaginal bleeding. Pregnancies were followed up until the final outcome was known. Antenatal, delivery, and neonatal outcomes were obtained from hospital records. We calculated adjusted odds ratios (aOR) using logistic regression with correction for maternal age. RESULTS: We recruited 1003 women. After excluding first trimester miscarriages (N=99), terminations (N=20), lost to follow up (N=32) and withdrawals (N=5), 847 pregnancies were analysed. Adverse antenatal complications were observed in 166/645 (26%) women with pain and/or bleeding, and in 30/181 (17%) women without (aOR=1.79, 95% CI=1.17-2.76). Neonatal complications were observed in 66/635 (10%) women with and 11/176 (6%) women without pain and/or bleeding (aOR=1.73, 95% CI=0.89-3.36). Delivery complications were observed in 402/615 (65%) women with and 110/174 (63%) women without pain and/or bleeding (aOR=1.16, 95% CI=0.81-1.65). For 18 of 20 individual antenatal complications, incidence was higher among women with pain and/or bleeding, despite the overall incidences being low. Nausea and vomiting in pregnancy showed little association with adverse pregnancy outcomes. CONCLUSIONS: Our study suggests that there is an increased incidence of antenatal complications in women with pelvic pain and/or vaginal bleeding in the first trimester. This should be considered when advising women attending early pregnancy units. This article is protected by copyright. All rights reserved.