Menstruation delayed by seven days each month and no yolk sac at six weeks of pregnancy may be normal, but poor embryonic development cannot be ruled out and can be dealt with by continued observation and termination of pregnancy. Due to irregular menstrual cycles, ovulation will be delayed accordingly, so the time of conception may be late and the development of the fetus will also be late. At this time, you can continue to observe for a week and then review the ultrasound again to see if there is a yolk sac. If the embryo is underdeveloped, there will also be no yolk sac at six weeks of pregnancy, which needs to be combined with the progesterone and blood HCG test, and the pregnant woman may also be accompanied by abdominal pain, vaginal bleeding and other abnormalities. If the embryo is underdeveloped, terminate the pregnancy if necessary. If a pregnant woman’s menstrual period is delayed for seven days each month, and there is no yolk sac in six weeks of pregnancy, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor, complete the relevant examinations, clarify the cause of the disease, and provide symptomatic treatment.