What is the duration of the first trimester of pregnancy?

The first trimester of pregnancy lasts from the first week through the end of the twelfth week. This period is crucial as it encompasses the early stages of fetal development, where significant changes occur, including the formation of major organs and structures. Understanding this timeframe helps healthcare professionals monitor maternal and fetal health effectively during those initial months. Consequently, the duration of 1 to 12 weeks accurately reflects the commonly accepted definition of the first trimester in obstetric practice.