2006-09-18 17:03:48 · 9 answers · asked by manglebaby1983@sbcglobal.net 1 in Pregnancy & Parenting ➔ Pregnancy
They measure the fetus from head to rump and that early in pregnancy all fetuses are the same size on the same days. It is only later that big babies are big and small babies are small. So if you have a X cm long baby then you are X amount of days/weeks. THey ask you for the date of your LMP (last menstrual period) so they can see if you are correct and they have a place to start.
2006-09-18 17:07:09 · answer #1 · answered by Oak18 2 · 1⤊ 0⤋
The LMP (last menstrual period) date is compared to the ultrasound picture of your baby. They look at the size and formation of the embryo and compare that age to the date of your LMP. They compare the two and if the date of your last period is different by a decent amount from the size and formation of the embryo, then further tests may be necessary. If your LMP is the same as the ultrasound age, then all is well and you have a cuddly miracle in a matter of months!
I've attached a cool site that gives little updates along the way.
2006-09-18 17:13:09 · answer #2 · answered by 101pupil 2 · 1⤊ 0⤋
They measure the embryo and can see how developed it is. The size and development along with the date of your last period give them a usually pretty accurate estimated due date. And it is an "estimated" due date.
2006-09-18 17:51:54 · answer #3 · answered by Redneck-n-happy 3 · 0⤊ 0⤋
It doesen't. Your doctor calculates your aproximate due date from when you had your last period.. The actual term of a pregncy is 39.2 weeks, (9 1/2 months) for humans, so your doctor can guess at your due date from knowing when you had your last period. The timing is usually within a week of when your expected delivery date is.
2006-09-18 17:13:51 · answer #4 · answered by janet g 1 · 1⤊ 0⤋
The due date is determined by the precise measurment of the the fetus (baby). The doctor only asks you to get an idea of how far along you are.
2006-09-18 17:10:23 · answer #5 · answered by Anonymous · 1⤊ 0⤋
The ultrasound simply goes on fetal growth and development. Your doctor and the ultrasound can be completely different but usually the doctor is more accurate.
2006-09-18 17:07:15 · answer #6 · answered by mommy of 3 boys 3 · 0⤊ 1⤋
They measure the size of the embryo and sac. Its all a guess and from your last period and size of the embryo they get a good date.
2006-09-18 17:06:28 · answer #7 · answered by anonbealove 3 · 1⤊ 0⤋
They measure the size of the baby or embryo (depending on which stage your at) and by size they can tell how far along you are. I think they also measure the size of ur uterus ect. But the "due date" is always approximate! CONGRATS!
2006-09-18 17:05:38 · answer #8 · answered by Anonymous · 2⤊ 0⤋
I think that tells you when you conceived.
2006-09-18 17:05:24 · answer #9 · answered by tomgurl2006 2 · 0⤊ 2⤋