How accurate are dating scans at 13 weeks
If there is a difference of one week or more, the ultrasound estimate is considered (4).
As you near the due date, you may have to start counting your pregnancy by days as – 39 weeks one day, 39 weeks two days, and so on (6).
If you miss your first period, you are likely to be four weeks pregnant (including two weeks of menstruation and ovulation) (2).[ Read: Pregnancy Due Date Calculator ]Pregnancy is calculated based on your last menstrual period.
Week one of your pregnancy will start on the first day of your LMP. This may sound weird but it helps in giving the exact date for timely medical care.
It gives you the estimated conception date and estimated due date along with the weeks of each trimester.
It will also show your current pregnancy week, and many more weeks you have to reach a full-term pregnancy.[ Read: Growth Scan During Pregnancy ] You can start counting pregnancy weeks as soon as you calculate your due date based on your LMP.