Missing one's period calls for an immidiate pregnancy test. An early visit to a doctor or an early ultrasound is important to confirm that the pregnancy is in the uterus. This is because at times, the gestation can be in extra uterine locations like the fallopian tubes or ovaries etc. These cases of ectopic pregnancy need urgent medical attention and if detected in time , can prevent catastrophic hemorrhage and at times succeed in avoiding surgery as well.
If the fetus is viable at that time , then there is a 95% chance that this pregnancy would go on to term.