An estimated due date can be calculated by following steps 1 through 3: First, determine the first day of your last menstrual period. Next, count back 3 calendar months from that date. Lastly, add 1 year and 7 days to that date.

How is pregnancy date worked?

Most pregnancies last around 40 weeks (or 38 weeks from conception), so typically the best way to estimate your due date is to count 40 weeks, or 280 days, from the first day of your last menstrual period (LMP). Another way to do it is to subtract three months from the first day of your last period and add seven days.

What is the earliest you can have a healthy baby?

In general, infants that are born very early are not considered to be viable until after 24 weeks gestation. This means that if you give birth to an infant before they are 24 weeks old, their chance of surviving is usually less than 50 percent. Some infants are born before 24 weeks gestation and do survive.