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Dr. Andrew Rynne

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Is a difference in dates of ultrasound and LMP a cause for concern?

Answered by
Dr.
Dr. Nishikant Shrotri

OBGYN

Practicing since :1968

Answered : 2916 Questions

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Posted on Sat, 3 Sep 2016 in Women's Health
Question: My ultrasound and lmp are four days different. My LMP was 12-16 but my ultrasound is saying it was12-12. I had a 20 week ultrasound and the doctor changed my due date to 9-17. Why? Also when I found out I was pg my hcg level was 258, how far along was I then?
doctor
Answered by Dr. Nishikant Shrotri 24 minutes later
Brief Answer:
Every thing within normal limits

Detailed Answer:
Dear XXXXXXX

Please do not get disturbed by a difference of dates in clinical method and ultrasonography.

The ultrasonography estimates the age of the baby by its different measurements. This can have a variation of about 4-7 days at different stages of pregnancy.

LMP is a rough guide for estimating the DD of delivery. In fact the egg is released 14 days prior to the next expected menses. It has got a life of 24 hours while the sperms are active for 72 hours. Hence any day within a period of a week around the day of ovulation, fertilization can take place, which is not possible to pinpoint clinically.

Considering this, you will realize that there is always going to be variation of about 4-10 days between these two methods calculations.

Moreover, the delivery can take place anytime between 3 weeks before to one week after the calculated due date. So change in calculation of DD by few days is not going to make any different.

Hence, please do not make any issue about the reported variations. They give calculations nearest to the perfect. Your calculations are within normal limits.

And now about hCG levels: They are never predictive of the duration of pregnancy. They have got a diagnostic value of existence of and well being of pregnancy. Any values above 25 mIU/ml are diagnostic of pregnancy ands these values are expected to continue to increase in normally growing pregnancy.

This should clarify your doubts. If you want to have any more clarifications, please feel free to ask me, XXXXXXX

I am sure, with this information, you would not hesitate in posting a good remark for me with 5 stars rating.

Dr. Nishikant Shrotri
Above answer was peer-reviewed by : Dr. Prasad
doctor
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Follow up: Dr. Nishikant Shrotri 23 minutes later
Thanks for your response. So pretty much I can go by my lmp for my due date instead of the ultrasound. The doctor is saying the baby is measuring "big", so that could be off as well?
doctor
Answered by Dr. Nishikant Shrotri 41 minutes later
Brief Answer:
Look for diabetes

Detailed Answer:
Dear XXXXXXX

Since the introduction of ultrasonography, we prefer to go by ultrasonography calculations since they are based on the age of the baby.

If the baby is appearing rather 'bigger' (large for the date), my sincere advice to you is to get yourself screened for diabetes. In many a prediabetic women (when the diabetes is in latent phase) in spite of absence of any clinical signs of diabetes, the baby attains larger size and weight and still behaves like a premature child. Such mothers and their babies are at a higher risk of pregnancy. Please request your Gynaecologist to perform a Glucose tolerance test on you which will sort out the matter. You may please upload the reports of the test for my review.

Please do not ignore 'large' for date baby.

For any more information, I am always available for you, XXXXXXX

Dr. Nishikant Shrotri
Above answer was peer-reviewed by : Dr. Prasad
doctor
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Follow up: Dr. Nishikant Shrotri 2 hours later
Dr. Shrotiri,
I am not diabetic. I have had the screening done twice. His father was an 11 pound baby. On my last scan I was 34 weeks and 2 days (which is off bc my LMP was 12-16-16). I got my first scan at 20 weeks which he changed my LMP to 12-12-16....
doctor
Answered by Dr. Nishikant Shrotri 19 minutes later
Brief Answer:
Please get your husband investigated

Detailed Answer:
Dear XXXXXXX

Alteration by 4 days is no change in expected due date as I had mentioned earlier.

You may not be diabetic at present, but could be in latent phase of diabetes which can be detected only by complete Glucose Tolerance Test.

Since your husband also was overweight at birth, it is possible that he might be having both recessive genes of diabetes. Please get him investigated for Glucose Tolerance Test.

And you may ignore the USG and LMP derived DD difference.

Dr. Nishikant Shrotri
Above answer was peer-reviewed by : Dr. Arnab Banerjee
doctor
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