Calculate due date dating scan

My ob-gyn at the time liked to do an ultrasound during every visit.After my second scan, she changed the due date to March 4.Here you will be given a scan and receive an accurate date for your baby's birth.

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Calculate due date dating scan

I thought that was kind of weird, but I was pregnant for the first time and figured this was just something that happened.

But during the next visit, she changed it again—to March 6.

Another options is for you or your doctor to try to calculate your due date based on the date you conceived (they just add 266 days to that), Greves says. A big factor is how regular your periods are, Lamppa says.

But of course this one can be a little complicated. “Dating by a last menstrual period is really based on a woman having 28-day cycles and ovulating on day 14,” she explains. If you don’t have regular periods or got pregnant right off of birth control, your doctor may give you an initial due date using the date of your last menstrual period and then tweak it after performing an ultrasound during the first trimester to assess the gestational age of baby, Greves says.

This 3-step method is referred to as Naegele's Rule and is based on a normal 28-day menstrual cycle.

Therefore, dates may have to be adjusted for longer or shorter menstrual cycles.

But it becomes much more important to have a correct due date when you get closer to term, Lamppa says—and not just for your ability to plan for a new baby.

“Providers make many decisions regarding timing of delivery, and it’s all based on your gestational age,” she says.

“Outcomes are improved for both moms and babies when due dates are accurate,” Lamppa says.

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