How many weeks into a pregnancy can the gestational sac be seen on a B-ultrasound?

　　Under normal circumstances, a gestational sac can be observed via ultrasound at around 5-6 weeks of pregnancy, although the exact timing may vary.

　　Typically, at about 5-6 weeks of pregnancy, which corresponds to approximately 35 days after the last menstrual period, the gestational sac can be detected by transvaginal ultrasound. This is because the gestational sac has formed and can be identified within the uterus at this stage. If an abdominal ultrasound is used, it may be necessary to wait until around 6 weeks of pregnancy to clearly visualize the gestational sac, as abdominal ultrasound has relatively lower resolution.

　　For women with regular menstrual cycles, the gestational sac is usually seen slightly later on abdominal ultrasound—often around 6 weeks or even later, at about 42-45 days. This is because abdominal ultrasound must pass through multiple layers of tissue such as abdominal fat and muscle, resulting in reduced image clarity. The gestational sac must develop to a certain size before it can be clearly visualized.

　　It is important to note that even in women with regular menstrual cycles, if conception occurs later than usual, the visualization of the gestational sac may also be delayed accordingly. Pregnant women are advised to undergo regular check-ups, which are beneficial for both maternal and fetal health.