There are many reasons for not being able to see the pregnancy sac during ultrasound after 41 days of menopause, mainly including short gestational week, insufficient filling of pregnant woman’s bladder and ectopic pregnancy (ectopic pregnancy), etc. 1. Short gestational week: If the pregnant woman has a long menstrual cycle, which generally means more than 30 days, or irregular menstrual cycle, ovulation will be late and the corresponding conception time will be delayed, at this time the gestational week is short, resulting in a small pregnancy sac that cannot be seen. In this case, it is suggested that pregnant women should do HCG examination first, and if the doubling of HCG meets the pregnancy standard, the examination can be repeated again after 1 week; 2, pregnant women’s bladder is not full enough: when performing abdominal ultrasound, pregnant women need to hold urine to ensure that the bladder is completely full in order to make the uterus imaging clear so as to see whether there is a pregnancy sac, so if pregnant women’s bladder is not full enough, the pregnancy sac may not be seen, therefore, vaginal Therefore, vaginal ultrasound can be performed for further judgment; 3. Ectopic pregnancy: If the pregnancy is ectopic (ectopic pregnancy), the gestational sac cannot be seen in the uterus, and blood HCG test should be performed in time to understand the doubling of HCG. If the doubling of HCG is good, it may be a late conception, and the pregnant woman can wait for 1 week before having a recheck. If the doubling is not good, progesterone, transvaginal ultrasound and posterior fornix aspiration should be performed to determine whether the pregnancy is ectopic or not, and if it is ectopic, surgery should be performed to terminate the pregnancy in time to avoid threatening the life of the pregnant woman. No matter which condition causes the inability to see the pregnancy sac, the pregnant woman needs to do the necessary tests before she can get the accurate result. Therefore, before the result comes out, the pregnant woman should not worry too much, just pay attention to rest and relax.