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 7 days.
3 weeks pregnant, a belly isn't really a thing. Though you may feel a bit bloated, most pregnant women don't start to show until around week 12
Date of conception: You have probably conceived around the time of your ovulation, which is around day 14 of the average 28-day menstrual cycle. If you know the exact date, allow 273 days (39 weeks) to get an estimate of your expected due date.
If the baby is born this week, it is still considered premature, but usually does not require special postpartum care. All internal organs are functioning, and respiration and the immune system work independently.
The average length of human gestation is 280 days, or 40 weeks, from the first day of the woman's last menstrual period. The medical term for the due date is estimated date of confinement
Your weeks of pregnancy are dated from the first day of your last period. This means that in the first 2 weeks or so, you aren't actually pregnant – your body is preparing for ovulation (releasing an egg from one of your ovaries) as usual.