When Can You See a Fetus on Ultrasound After Conception?

Q: When Can You See a Fetus on Ultrasound After Conception?

Hello： A normal pregnancy test can detect pregnancy around the time your period is due, while an ultrasound can typically show results about a week later. <br>Therefore, if your menstrual cycle is regular, you should be able to test positive for pregnancy on February 14. <br>An u

How long after fertilization can an ultrasound be performed? Thank you!

Hello Doctor: My last menstrual period started on January 14.
I tested for ovulation on February 2 and 3 and saw two lines.
I had intercourse on February 1 and 3.
My basal body temperature started to rise on February 4, and since today, February 25, my temperature has been around 36.6 to over 37 degrees Celsius.
I had an ultrasound on February 24, but no embryo was detected.
Should I calculate from my last menstrual period on January 14, or from the ovulation days on February 2 and 3? Or should I start counting from the implantation or fertilization day? I'm a bit worried since I haven't seen anything yet.
My abdomen doesn't hurt, and there is no bleeding.
Is there still a possibility of an ectopic pregnancy? How long should I wait before getting another ultrasound?

Xunwen, 20~29 year old female. Ask Date: 2015/02/25

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello: A normal pregnancy test can detect pregnancy around the time your period is due, while an ultrasound can typically show results about a week later.
Therefore, if your menstrual cycle is regular, you should be able to test positive for pregnancy on February 14.
An ultrasound would be able to detect it by February 21.
If you haven't seen the embryo by February 24, there is a possibility of an ectopic pregnancy.
It is recommended to have a blood test to check the hCG levels and follow up with an ultrasound.
Wishing you good health.

Reply Date: 2015/02/25

More Info

To determine when you can see a fetus on ultrasound after conception, it is essential to understand the timeline of pregnancy development and the limitations of ultrasound technology. Typically, pregnancy is calculated from the first day of your last menstrual period (LMP), which in your case is January 14. This method is standard practice because it provides a consistent reference point for healthcare providers.

After conception, which usually occurs around the time of ovulation (in your case, around February 2-3), it takes about 6 to 7 days for the fertilized egg to travel down the fallopian tube and implant itself into the uterine lining. This implantation process is crucial, as it marks the beginning of a viable pregnancy. Once implantation occurs, the body starts producing the hormone hCG (human chorionic gonadotropin), which is what pregnancy tests detect.

Regarding ultrasound, it is generally recommended to wait until at least 5 to 6 weeks after your last menstrual period to perform a transvaginal ultrasound, as this is when a gestational sac can typically be visualized. By this time, you should be able to see the gestational sac, and possibly even a yolk sac, which indicates that the pregnancy is progressing normally. A fetal heartbeat can usually be detected around 6 to 7 weeks of gestation.

In your case, since you had your last menstrual period on January 14 and are currently at the end of February, you would be approximately 6 weeks pregnant based on the LMP calculation. However, if you are calculating from the ovulation date, you would be around 4 weeks post-ovulation. This discrepancy can lead to confusion regarding the visibility of the embryo on ultrasound.

If you had an ultrasound on February 24 and did not see any signs of a gestational sac or embryo, it may be too early, especially if you are calculating from the ovulation date. It is also important to note that if you are experiencing no pain or bleeding, this is a positive sign. However, it is essential to follow up with your healthcare provider for further evaluation.

As for the concern about an ectopic pregnancy, it is crucial to monitor for symptoms such as abdominal pain, shoulder pain, or vaginal bleeding. If you experience any of these symptoms, you should seek medical attention immediately. Ectopic pregnancies can be life-threatening if not treated promptly.

In conclusion, based on your last menstrual period, it is advisable to wait a little longer before having another ultrasound, ideally around 7 weeks from your LMP, to allow for better visualization of the pregnancy. If you have any ongoing concerns or symptoms, do not hesitate to reach out to your healthcare provider for further guidance and support. They may recommend a follow-up ultrasound or blood tests to monitor hCG levels, which can provide additional information about the status of your pregnancy.

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