Usually, women with regular menstruation can see the fetal buds and fetal heartbeat by ultrasound when they stop menstruation for 40-50 days, but some women have delayed menstruation or abnormal menstrual cycle, some women have menstruation for 40-50 days, or even only once every 2 months, which delays the ovulation of this part of the women, delays the fertilization of the egg bedding, and delays the appearance of fetal heartbeat and fetal buds accordingly, and it may appear that the pregnancy is 80 days old. This may lead to the situation of fetal heartbeat and buds only occurring after 80 days of pregnancy. For pregnant women with irregular menstrual cycles, it is inaccurate to calculate the week of pregnancy from the time of menopause. The actual week of pregnancy should be estimated from the ultrasound examination conducted in the early stage of pregnancy, so as to estimate the time for various pregnancy tests and the expected date of delivery. To summarize, it is normal for a pregnant woman with abnormal menstrual cycle to have fetal heartbeat and buds on the 80th day of pregnancy, but she should pay attention to regular pregnancy checkups, and do all the tests on time, such as glucose test, Down’s syndrome, four-dimensional ultrasound and other tests, in order to rule out the abnormalities of fetal developmental delays as early as possible, and to have a smooth pregnancy.