Few women know exactly when they became pregnant. Even if you approached conception responsibly, measured the basal temperature chart and chose the most favorable day, variations still occur in married life. And ovulation may go astray and the cycle may be late, or even not start at all, due to breastfeeding - yes, mothers, they also get pregnant during lactation. Meanwhile, pregnancy management is an exact science, especially in the first trimester. At 5-6 weeks, a heartbeat appears and the embryo is visible on ultrasound; if it is not there, then the pregnancy has not occurred or has frozen. The calculation of the due date depends on the duration of pregnancy.