Can pregnancy ultrasounds measure my gestational age?

Hello,

Welcome to icliniq.com.

I have read your query and will guide you in your case. Let me guide you with the information you gave. Your normal menstrual cycle length is 25 days, and you had a period within the last ten days three months back. It means the expected period in the subsequent month would be around the middle, and ovulation would have happened two weeks early, that is, around the beginning of the month. The ovulation period is the fertile period of the female. The calculated ovulation day falls between your sexual intercourse days in the subsequent month, and this would have resulted in present pregnancy. Sexual intercourse done three months back cannot result in a pregnancy as you had your period one day after the sexual intercourse.

Ultrasound measurement of the embryo or fetus in the first trimester is the most accurate method to establish or confirm gestational age. In this ultrasonography, the gestational age and estimated due date (EDD) can be determined. If you have already done ultrasonography, you can see the gestational age in the report, and you can match the gestational age from the calculated ovulation date in terms of age, and it will help you relieve your anxiety. Hope you find my reply helpful.

Please follow up if you have a further related query.

Take care.

Thanks.

Hello,

Welcome back to icliniq.com.

Your current pregnancy is not due to the sexual intercourse done three months back and is due to the intercourse after that. This is because you got the period the very next day of your intercourse. And also those dates are not in your fertile time period. I saw the Doppler scan report (attachments removed to protect the patient's identity). I cannot interpret the report in terms of age because it requires measurement, which is then interpreted in terms of weeks and days of the age of the baby. Doppler scan detects blood in the vessels. It is used in pregnancy to study blood circulation in the baby, uterus, and placenta. To measure the gestational age, CRL measurement is done in the first-trimester scan between 6 to 13 weeks of pregnancy, and it is the most accurate estimation of gestational age in early pregnancy. You should ask your treating physician to do transvaginal ultrasonography (TVS) scan in the ongoing first trimester to estimate gestational age, and various developments and growth of the baby can be assessed according to the present gestational age of the baby. I hope now my explanation about present pregnancy helps to clear your doubt.

Please follow up if necessary if you have any other related queries.

Wish you happy and safe pregnancy.

Take care.

Thanks.

Hi,

Welcome back to icliniq.com.

I have read your query. The days you had mentioned that you had sex three months back do not fall under the fertile period. Let us explain this further. You had a period towards the last ten days of the month. It means you would have ovulated 14 days before the start of the period. Your fertile days do not fall under the days you had sexual intercourse. Hence possibility is unlikely or very less. Sperm can survive upto five days in the women's body. It means if the semen was deposited inside by the sexual intercourse then also it cannot result in positive pregnancy because of two reasons first, period commenced on that very day and second, the next ovulation date was after 14 days, which is far away for sperm to survive upto the above ovulation timing. On the contrary, you had sexual intercourse everyday in the subsequent months and this most highly likely explains the present positive pregnancy because it was done during your fertile days. I have tried to explain you in the most precise manner, and I hope it helps you. Since you are currently in, first trimester, the transvaginal ultrasound (TVS) scan which is done between the 6th and 13th weeks of pregnancy will give you the gestational age of the baby and other overall growth and development information and various other pregnancy parameters. Hope you find my reply meaningful. Please follow up if you need further guidance on similar health-related query. After you do the TVS scan, you can send the report if you want to ask any queries related to it.

Take care.

Thanks.

Hi,

Welcome back to icliniq.com.

Sorry for the delay in the reply. The CRL measurement is 68.1 mm. In the report, the CRL measurement would be converted into the weeks and days, referring to the gestational age of the baby. Gestational age is not the same as fertilization age. It takes about 14 days from the first day of the last menstrual period for conception to take place and is thus two weeks shorter than the gestational age. What is the age in weeks mentioned in the report? Can you attach the ultrasonography report?

At 68.1 mm, the gestational age is around 13 weeks, so the fertilization age would be 14 days shorter, that is 11 weeks. If ovulation had happened around the beginning of the month, two months ago, then the total weeks by now would be ten weeks and three days, and this would be the fertilization age of the baby, and gestational age would be two weeks more. Now you can match with the report about what gestational age is mentioned, and that would decide your ovulation and dates of sexual intercourse leading to positive pregnancy. I hope you find my reply helpful. Please follow up if you have a further related query. Thank you.

Hi,

Welcome back to icliniq.com.

In the report, the gestational age is mentioned as 13 weeks one day as of midday before four months, which means two weeks minus is 11 weeks one day, that is 78 days is the fertilization age. Therefore, the calculation of days are: 31 days + 28 days + 19 days = 78 days. It would mean 78 days of fertilization age if the date of conception was four months back. The above date falls during the sexual intercourse done three months ago. Therefore, it is the most likely reason for the present positive pregnancy. In my opinion, earlier sexual intercourse is not the reason. So, the date of the history of sexual intercourse and CRL measurement of 68.7 mm showing gestational age of 13 weeks one day denotes the second exposure is the most likely reason for the positive pregnancy and not the earlier one. I hope I have given you a clear explanation for your query.

Kindly revert in case of further queries.

Thank you.

Hi doctor,

Thank you for the reply.

I received your query today, but I see that you posted the follow-up query five days ago. So let me explain to you through a basic example. In an ideal situation, the menstrual cycle length is 28 days, the preovulatory period varies, and on mid of cycle ovulation happens, and the post-ovulatory period is always constant. So in a 28-day cycle, both pre and post-ovulatory length is 14 days each. Still, in a real-life situation, the menstrual cycle length is not 28 days, and hence pre, and post-ovulatory length varies. Therefore, it can be challenging to know exactly when ovulation occurs. The gestational age is calculated from the first day of the pregnant person’s last menstrual period (LMP) to the present day.

Your ultrasound (USG) report (attachment removed to protect the patient’s identity) says gestational age is 13 weeks and one day, which means two weeks minus 11 weeks, and one day is the fertilization age. This equates to the date towards the end of the month before three months as the ovulation day. Since the preovulatory period can vary, you had menstrual bleeding towards the mid of the month, three months ago, and the calculated expected ovulation day from USG was somewhere at the end of that month. So it means you had ten days of preovulatory period. So instead of subtracting two weeks, the first day of your LMP would be the mid of the month, three months ago, as you have calculated above in the query, but it is actually three days later. So we have to subtract ten days instead of two weeks from the calculated USG gestational age. So, after all these calculations, in my opinion, the present positive pregnancy is due to sexual intercourse done towards the end of the month three months ago or the beginning of the month, two months ago.

I hope I have made you understand. Please follow up if you have any further related health queries, and do ask your primary care doctor or obstetrician to know more about it, and you can let me know their opinion about it.

Take care.

Thank you.

Hi,

Welcome back to icliniq.com.

I understand your concern. The earlier first-trimester scan with CRL measurement and this scan done today(attachment removed to protect the patient’s identity) give almost the same EDD and gestational age of the baby. CRL measurement is the best USG (ultrasonography) parameter to determine the gestational age compared to other biometric variables done in the subsequent trimester. What we can confirm is that you had menstrual bleeding after the intercourse mid of the month three months ago. And that intercourse did not result in a pregnancy as menstrual bleeding can only happen if the released egg is not fertilized. Bleeding means the superficial layer of the endometrium has been lost in the form of menstrual bleeding. It means the endometrium is thinned out due to bleeding, and it should be around 10 mm at the time of implantation of the fertilized egg. I have given some physiological facts to strengthen the concept that how earlier intercourse cannot result in pregnancy. So from a physiological point of view also present pregnancy is not due to intercourse done on the above dates.

In calculation, we do two weeks minus from gestational age, assuming that the cycle length is of 28 days and ovulation has occurred in mid of the cycle. Also, I mentioned in the last chat that the post-ovulatory days are constant that which is of 14 days. In your case, you can minus two weeks from the given gestational age from the USG as your cycle length is not ideal at 28 days. Rather, it is variable, so it is challenging to know the exact date of ovulation day and hence the fertilization date. This I have tried to explain in the last chat. But whatever the ovulation date may be, it would have occurred around the end of the month, three months ago. So, in my opinion, the present pregnancy is due to the sexual intercourse done between the end of the month three months ago or the beginning of the month, two months ago, based on the history of your menstrual cycle, LMP, and USG findings. Have you asked your primary care doctor about the present query? If yes, what is your doctor’s view regarding it?

I hope you find my reply helpful. Please do follow up if you have any further related health queries. Take care. Thank you.

Hello,

Welcome to icliniq.com.

I understand your concern.

The non-invasive prenatal testing (NIPT) is highly accurate. It uses cell-free DNA in the maternal plasma and then extraction of cell-free fetal DNA (deoxyribonucleic acid) from it and with the application of massively parallel sequencing (MPS) and single nucleotide polymorphisms (SNPs) and various methods to determine the paternity prenatally. Unfortunately, I know little about this latest technology using the above genetic methods to find paternity through cell-free DNA (cfDNA). 99.9 % accuracy means the test is a very high standard.

Regarding 0.1 %, it may be some technical procedure difficulty or a sample containing less amount of fetal DNA not enough to determine loci of SNP, etc. But as I said, I do not know much about it in detail. So I cannot confirm what 0.1 % refers to in the above NIPT test. Sorry, this time I am not able to guide you. You can ask the same query from the laboratory doctor where you gave the sample, what it means, and the interpretation in terms of the test result, and they would be in a better position to guide you regarding it. Anyway, your decision is appropriate, and after the results are back from the laboratory, you will get complete peace of mind. You can enjoy pregnancy without a shadow of any doubt regarding it. Thank you.