If you usually have regular menstrual cycle, which is once in 28-30 days, if you have intercourse before ovulation, then around 31 or 32 days after menopause, the blood HCG will be elevated by blood test. However, an increase in blood HCG does not necessarily mean that the pregnancy is intrauterine, so it is advisable to have another blood test every other day. If the blood HCG doubles from the original level, then there is a high probability of intrauterine pregnancy. If the blood HCG rises just a little bit from the original level, you must be highly alert to the possibility of ectopic pregnancy and it is recommended to give further monitoring of the blood HCG and if necessary, hospitalization for observation. It is also recommended that the location of the gestational sac can be determined by ultrasound examination around 45 days after menopause to determine whether the pregnancy is intrauterine or extrauterine.