Get E-Book on COVID-19

Q. LMP was noted mistakenly 10 days later than the actual LMP. Will it affect NT test result?

Answered by
Dr. Sanjay Kumar Bhattacharyya
and medically reviewed by iCliniq medical review team.
This is a premium question & answer published on Dec 03, 2019

Hello doctor,

My menstrual date was on the 4th of the previous month, and I got married in the same month. This my pregnancy test becomes positive and during my abdominal scan doctor said that my baby's NT rate is 3.17 and the nasal bone is short. Five days later again I have done a scan in that my NT rate came as 2.1 mm and nasal bone is ossified, the result was satisfactory. But mistakenly the ultrasound technician put my LMP date 10 days after my actual date. Without noticing it, we have done a double screening and the result came as low risk. Today I went to the hospital to give a blood sample for triple screening, then only we noticed the mistake on the LMP date of ultrasound. Will it affect my triple screening result? Does it mean my double screening test was wrong?

Dr. Sanjay Kumar Bhattacharyya

Obstetrics And Gynaecology


Welcome to

I have seen your reports. (attachment removed to protect patient identity).

During the first scan, your baby was 11 weeks and the NT (nuchal translucency) was 3.17. That was a high value but it has been seen in nine out of ten babies with thickness 2.5-3.5 mm at 11 weeks will be normal. The next scan shows your NT was 2.1 mm and your period of gestation 12 weeks. As per your truly calculated fetal age, this was low risk.

At 12-13 weeks, the normal value is 7mm (50th percentile thickness), 2.8mm (95th percentile thickness). So considering these two values only, you are not at high risk.

But I must tell you that the measurement of nuchal translucency alone is less effective for first trimester screening than the combined test (nuchal translucency measurement and biochemical markers). But definitely for this, there is a need to mention the true LMP (last menstrual period). Otherwise, there will be again a mistake and just like the previous one you have to recalculate the whole.

Was this answer helpful?


Thank you doctor,

So it means I have to perform an ultrasound again? Will this ultrasound gives me the correct value? What about the triple screening test that I have done today? Will it give a correct value or not?

Dr. Sanjay Kumar Bhattacharyya

Obstetrics And Gynaecology


Welcome back to

The value of the triple screening test depends on two factors. First of all, the ultrasound age of the fetus and secondly the date of your missed cycle (which is erroneous). The ultrasonologist assess the fetus in contrast with your last date and optimize the fetal age with the help of that value. So, as you can see, everything changes with the date of your last cycle and it is very crucial.

I suggest a back-calculation. If you are found low risk, do not worry. But if you are found in high risk you have to rescore the value again as I have told you. It overtly depends on your last cycle date.

Was this answer helpful?


Related Questions:
If rubella IgG is positive, am I at the risk of TORCH infection?
Is NIPT required in the second trimester?
Kindly explain my NT scan and double marker blood test reports in detail.
Consult by PhoneConsult by Phone Video ChatVideo Chat
Also Read Answers From:

Comprehensive Medical Second Opinion.Submit your Case

Related Questions & Answers

As the scan was clear, had Medroxyprogesterone to get period. Now, UPT is positive. What to do?

Query: Hello doctor, I am 26 years old. I went to my PCP for a pregnancy test and it was positive. Had an ultrasound a few days later and the technician said he did not see pregnancy in my uterus so he performed a transvaginal ultrasound to see if I was pregnant in my uterus but I was not. I took a pregna...  Read Full »

Will I get my periods correctly by next cycle?

Query: Hello doctor, I had a medical abortion about two months back. Last month, I did not get my natural periods. So, this month I took the tablet Primolut N and got my period. I took FSH and LH test and it was in 1:1 ratio. On the 12th day of my LMP, I took a follicular scan. There was no follicle seen ...  Read Full »

Do my wife's NT scan and double marker test results show a high risk for Down's syndrome?

Query: Hi doctor, My wife had NT scan and double marker test at 12 weeks and 3 days of pregnancy. The report is as follows, CRL is 59.2 mm, NT is 1.45 mm, free beta-hCG is 84.84 IU/L, equivalent to 2.217 MoM and PAPP-A 0.712 IU/L equivalent to 0.282 MoM. Trisomy 21 is 1: 450 1:47 and trisomy 18 is 1: 5315...  Read Full »

Also Read

Can naked body to body massage spread HIV?
Hello doctor, I recently had some business trip during which I had some naked body to body massage wherein massager vag...  Read more»
Are COVID-19 Patients Infectious for up to 90 Days After Recovery?
There have been reports of recovered COVID-19 patients getting reinfected and testing positive for almost 3 months. Read...  Read more»
Crohn's Disease
Crohn's disease causes inflammation of the digestive tract, which results in symptoms like severe diarrhea, stomach pain...  Read more»

Ask your health query to a doctor online?

Ask an Obstetrician & Gynaecologist Now

* guaranteed answer within 4 hours.

Disclaimer: All health Q&As published on this website is not intended to be a substitute for professional medical diagnosis, advice or treatment by a trained physician. Seek the advice from your physician or other qualified health-care providers with questions you may have regarding your symptoms and medical condition for a complete medical diagnosis. Do not delay or disregard seeking professional medical advice because of something you have read on this website.