In most cases, the fetal heartbeat can be detected around 42 days of pregnancy, but the time to detect the fetal heartbeat may be delayed due to the different menstrual cycles of each woman, but most women can basically detect the fetal heartbeat around 50 days of pregnancy. For women with a delayed menstrual cycle, ovulation is often delayed, so the time of conception will be delayed, and the appearance of the fetal heartbeat will also be delayed. Therefore, the fetal heartbeat may not appear on the ultrasound examination on day 42 of pregnancy, and even the obvious gestational sac may not be visible. Especially for women with polycystic ovary syndrome, the time of menopause cannot be projected based on the last menstrual period because ovulation is scarce, and can only be projected backwards based on the gestational sac on the ultrasound examination. For women with a menstrual cycle of 28 to 30 days, an ultrasound can be performed at about 50 days of pregnancy to confirm the diagnosis, and under normal circumstances, the fetal heart can be seen. If the fetal heart is not visible at this time, then you can consider to check again after a week, if there is still no fetal heart, then you should consider the possibility of an empty sac.