Hello, and I hope I can help you today. The Clearblue test is not very accurate in predicting gestational age. The amount of pregnancy hormone in a woman s urine can vary depending on the time of day she did the test and how much water she had to drink before the test, so i would not rely on that test to determine how far along she is. Furthermore, many women have some bleeding in the first trimester of pregnancy, so the bleeding she had in December and January may not have been her real period at all. The most accurate way to test the age of a pregnancy, is an ultrasound exam to measure the fetus. This is normally done during the course of her routine prenatal care. An ultrasound is also necessary to determine if there is more than one fetus present. In your sister s case, if she conceived in November, the measurements of her uterus at this point would be accurate. So I would recommend that she have an ultrasound exam (which I am sure will be done soon as part of her routine prenatal care) to confirm her due date and the viability of the pregnancy. I hope I was able to adequately answer your question today and that my advice was helpful. Best wishes to your sister for her pregnancy, Dr. Brown