The demand for ultrasound in early pregnancy has been increasing steadily, and is now a routine investigation for most women within the first trimester of their pregnancy. It is a safe investigation which provides reassurance, charts normal development, and identifies women with abnormal or high risk pregnancies. Transvaginal ultrasound has revolutionized the diagnosis of early pregnancy as it can detect a pregnancy at an earlier stage, whether it is normal and therefore reassuring, or abnormal and require intervention. Ultrasound is also a useful tool to aid decisions regarding management of abnormal pregnancy, such as ectopic pregnancy or miscarriage. This chapter looks at the important role ultrasound plays in the diagnosis and management of abnormal pregnancy.