Does a ultrasound tell the exact weeks your baby is?

An ultrasound can provide an estimate of the gestational age of the fetus, which helps determine how many weeks pregnant a person is. The accuracy of this estimate is highest in the first trimester, where measurements of the embryo or fetus can closely correspond to gestational age. However, as pregnancy progresses, factors such as individual growth rates can lead to variations, making it less precise in later trimesters. Therefore, while ultrasounds are a valuable tool for estimating gestational age, they may not give an exact number of weeks.