QuestionHi,
I am right now 27 weeks pregnant.I went for routine Scan around 20th week everything came out well excepting that due to fetal movement the sonographer couldnot document Fetal heart.Hence i went again at 23 week 5 days & was informed that findingd are good.But Ultrasound determined my Gestational age to be 26 weeks 6 days +/_9 days.On every other scan my Geatational age as per LMP and as per Ultrasound matched. Why is this difference of 3 weeks? Could you advise.I am worried
AnswerDear Shanthi,
Determining gestational age is a rather in-exact science. Since most women don't know the exact date of conception, it is more reliable to use the 1st day of her last period to calculate gestational age than the date of conception. When a mother has a history of regular periods, and knows the 1st day of her last period, using the LMP calculation is usually pretty accurate.
Ultrasounds are typically the most accurate in determining gestational age EARLY in pregnancy (before 20 weeks). After that, variations in the baby's size or the size of a mother's uterus can throw measurements off a little. This would help to explain the +/- 9 days for you.
Keep in mind that a baby is considered "full term" after 36 weeks, even though the due date is calculated 40 weeks from the 1st day of the LMP. And the chance of your (or any) baby arriving on it's due date is very slim. You will find these precious creatures have their own time table for everything, including their birth date and time!
If it were me, I'd keep the LMP calculation in the back of my head, but be prepared to split the difference, so to speak. As I said, it's not an exact science. If the time comes and it's "on the bubble" of that 36 week mark as far as you are concerned, express the concern about the discrepancy in LMP and ultrasound dates to your doctor. Otherwise, PLEASE don't worry about it so much. Eat healthy, take your prenatal vitamins, and be ready to go +/- 3 weeks! :-)
Good Luck!
