Thirty days pregnant test paper strong positive, negative ultrasound can not see the gestational sac, may be a normal phenomenon, may also be ectopic pregnancy. 1. Normal reaction: generally in 35 ~ 40 days or so can see the gestational sac, if the current just 30 days, did not find the gestational sac, may be a normal performance. Because this time the gestational sac is very small, too early to do ultrasound is not always able to determine the location of the gestational sac. 2. Ectopic pregnancy: that is, the embryo in the uterus outside the place where the bed, test paper strong positive, check the ultrasound if you can not see the gestational sac, should be vigilant ectopic pregnancy, close observation of irregular vaginal bleeding and abdominal pain. Currently can not see the pregnancy sac can be observed, if 40 days after the hospital re-examination, still do not see the pregnancy sac, we must pay attention to, and actively find the cause, and then targeted treatment.