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Need to find out the gestational age from LMP

DOCTOR OF THE MONTH - May 2013
May 2013
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Practicing since : 2006
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I am trying to find out how accurate my conception/due date. my last lmp was september 5, 2011. i had my first ultrasound on November 2, 2011. The technician measured my crl at 1.38 cm. I had two other u/s after and it was measured by my gestational age from my lmp. My due date has been XXXXXXX 12, 2012 since my first doctor appointment and has never changed. Last week I measurd 38cm the week before was 39cm. I was just curious on when I actually conceived and how accurate the ultrasound is.
Posted Sun, 24 Jun 2012 in Pregnancy
 
 
Answered by Dr. Sree Gouri SR 46 minutes later
hi XXXXXXX,

thanks for the query.
-according to your last menstrual period September 5th, your due date will be 12th XXXXXXX as your doctor told, because due date will be 9 months and 7 days from lmp.
you might have conceived around 19th of September in case of regular cycles.

-by ultrasound,
due date can be measured +/- 1 week by first trimester scan,
second trimester scan will give due date with +/- 2 weeks variation and
due date by third trimester scan is not that much reliable.

so due date by lmp and by first trimester scan taken together will give most accurate date.

as the pregnancy progresses the head descends that may be the reason for your symphysio fundal height decreasing from 39cm to 38cm.
other cause could be decrease in liquor with progression of pregnancy.

but remember only 4% people will deliver on their due date, 80% will deliver in between 2 weeks prior to 1 week after the due date.

Hope I have answered your query. I will be available to answer your follow up queries. If you are satisfied with all my answer, please rate the answer after closing the discussion.
take care.
Above answer was peer-reviewed by
 
Follow-up: Need to find out the gestational age from LMP 6 minutes later
Thank you. It also had 7 w 5 d on the first ultrasound. Is that the implantation date, fetal age? Could that also be inaccurate ? I had sex on the 18 and 19
 
 
Answered by Dr. Sree Gouri SR 1 hour later
hi XXXXXXX,

the 7 weeks 5 days is the gestational age of the fetus at that time.

I am not saying that ultrasound wise due date is inaccurate,
what I meant to tell is instead of taking due date by lmp and due date by 1st trimester scan separately, if both are taken together,
means if both dates correlate it will be more accurate.

Wish you Good Health, If you are satisfied with my response please rate the answer after closing the discussion.
take care.
Above answer was peer-reviewed by
 
Follow-up: Need to find out the gestational age from LMP 4 minutes later
If the 7 d 5 w is the gestational age it doesn't match up to the gestational age of the lmp. That is saying the ga is September 23. The ga fromm lmp is sep 5. It makes no sense
 
 
Answered by Dr. Sree Gouri SR 24 minutes later
hi XXXXXXX,

if your scan was taken on November 2nd, that time gestational age is 7 weeks 5 days.
from your lmp on September 5th to November 2nd, the days are 58, means it comes as 8 weeks 2 days.

so, there is 4 days difference in the two,

as I told first trimester scan may give +/- 1 week difference,
there is 4 days difference between due date by lmp and due date by 1st trimester scan, this is almost correlating.

so as only 4% will deliver on the due date, you need not worry about this and take regular checkups for monitoring the well being of the baby.

Wish you Good Health, If you are satisfied with my response please rate the answer after closing the discussion.
take care.

Above answer was peer-reviewed by
 
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