Unplanned Pregnancy: Calculating Gestational Age and Conception Dates

I found out I was pregnant on July 14th, and I am currently 27 weeks and 4 days along?

Hello doctor, I would like to ask about a gynecological examination on July 14, 2022, where the cycle was noted as 27 weeks and 4 days.
The child has not had her menstrual period and we all thought she was just gaining weight (she is normally very thin).
I would like to inquire if the conception time was around the end of December last year or early this year, because the child mentioned that there was sexual intercourse on January 20, 2022.
However, the calculations do not seem to align with that date.
If intercourse occurred on January 20, then it would not be possible for the current cycle to be 27 weeks and 4 days.
Could you please help clarify this? Thank you.

Lu Mi, 40~49 year old female. Ask Date: 2022/07/16

Dr. Zhang Kunmin reply Obstetrics and Gynecology

Hello, the estimated due date and conception date are usually more accurate when calculated around 8-9 weeks of pregnancy.
However, the margin of error increases significantly in later weeks, so based on your description, it is not possible to accurately estimate the conception date.
It is still necessary for the pregnant woman to carefully recall the exact dates.
Thank you! Wishing you safety and health.
Dr.
Chang

Reply Date: 2022/07/16

More Info

Understanding unplanned pregnancies can be quite complex, especially when it comes to calculating gestational age and determining the conception date. Based on the information provided, it appears that there is some confusion regarding the timing of the last menstrual period (LMP), ovulation, and the actual conception date.

To clarify, gestational age is typically calculated from the first day of the last menstrual period (LMP). This method assumes a regular menstrual cycle, which is usually around 28 days, but can vary from person to person. In your case, if your last menstrual period was on July 14, 2022, and you are currently at 27 weeks and 4 days of gestation, this would suggest that you are approximately due around April 20, 2023.
If we consider the average length of a pregnancy, which is about 40 weeks, this would mean that conception likely occurred around 2 weeks after your last menstrual period, which would be around July 28, 2022. However, if you are suggesting that sexual activity occurred on January 20, 2023, this would not align with the gestational age of 27 weeks and 4 days, as that would be too late in the pregnancy to be the conception date.

It's also important to note that sperm can live inside the female reproductive tract for up to five days, which means that if you had sexual intercourse shortly before ovulation, it is possible to conceive even if the intercourse occurred a few days prior to the estimated ovulation date. However, if you are certain that the only sexual encounter was on January 20, it would not be consistent with the gestational age you provided.

In cases where menstrual cycles are irregular or if there is uncertainty about the timing of ovulation, ultrasound examinations can provide more accurate estimations of gestational age. Healthcare providers often use measurements of the fetus, such as crown-rump length (CRL) in the first trimester, to assess gestational age more accurately. If there is a discrepancy between the calculated gestational age based on LMP and the ultrasound findings, the ultrasound measurements are generally considered more reliable.

Given your concerns about the timing of conception and the gestational age, it would be advisable to consult with a healthcare provider who can perform an ultrasound and provide a more accurate assessment of the pregnancy. They can also help address any concerns you may have regarding the health of the pregnancy, especially if there are any complications or if you have a history of previous pregnancies that may have been complicated.

In summary, based on the information provided, if your last menstrual period was on July 14, 2022, and you are currently at 27 weeks and 4 days of gestation, it is unlikely that conception occurred on January 20, 2023. Instead, it is more plausible that conception occurred around late July 2022. If you have further questions or concerns, please reach out to a healthcare professional for personalized advice and care.

Similar Q&A

How to Accurately Determine Your Conception Date

The last menstrual period was on July 13. An ultrasound on September 6 showed a gestational age of 7 weeks and 0 days, with a margin of ±12 days (due date April 25 of the following year). Another ultrasound indicated a gestational age of 7 weeks and 3 days, also with a margin of ...

Dr. Huang Zifei reply Obstetrics and Gynecology
Dear M, Basically, it is not possible to accurately predict which day of unprotected intercourse occurred within three consecutive days using ultrasound, unless it is more than a week apart, which would make it easier to determine. I apologize for not being able to answer your ...

Calculating Conception Date Based on Due Date: A Guide

If the due date is September 20, the estimated conception date would be around December 27 of the previous year. Currently, you are at 19 weeks of gestation.

Dr. Cao Guotao reply Obstetrics and Gynecology
Hello, it should be around the end of December. Wishing you good health.

How to Calculate Your Due Date: A Guide for Expecting Mothers

How to calculate the due date?

Dr. Wang Jionglang reply Obstetrics and Gynecology
For women with a regular menstrual cycle, the estimated due date is typically calculated as: month + 9, day + 7 (for example, if the last menstrual period was on January 1, the estimated due date would be October 8). If the menstrual cycle is irregular, an early ultrasound can be...

Determining Possible Conception Dates Based on Irregular Menstrual Cycle

Based on your menstrual cycle irregularities, with periods on June 12, July 25, September 3, and no period in October, and a pregnancy test on January 2 showing 11 weeks and 5 days of gestation, the possible dates of conception would likely be around the time of unprotected inter...

Dr. Cao Guotao reply Obstetrics and Gynecology
Hello, based on the information you mentioned, it could possibly be related to the event on January 21st, but this is all speculative, and sometimes there can be a difference of a few days. Wishing you good health.