Foetal Pole: Pregnancy is an exciting time in the life of a mother, or a family expecting a baby. However, there are a lot of things that are always bugging people which we are addressing in this article. Pregnancy lasts between thirty-eight to forty weeks, calculated from the last menstruation. Pregnancies are simply detectable these days, usually via blood or urine testing. The first physical sign of a foetus will appear in the form of a structure called the foetal pole. At this point, the embryo is barely visible in a tiny comma shape. Sometimes, the foetal pole might not be visible through ultrasound scanning, but there is no need to be nervous.

What Is The Foetal Pole?

The foetal pole will appear in the fifth week of pregnancy as a 3 to 5mm thickening around the margin of the foetal yolk sac, which provides nutrition to the growing embryo. It is basically the structure that becomes the foetus. It has a rather curved structure, with the head at one end and a tail like formation on the other end. 

The distance between the head and tail which is called the crown-to-rump length is measured. The foetal pole will continue to grow at the rate of one mm per day, making its length a close approximation for the age of the foetus. The age is measured by adding the length of the foetus in mm up to 6 weeks. For example, if the foetal pole is 6 mm in length, then its age is six weeks and six days. However, this is only a rough idea of the age.

When Is It Seen On The Ultrasound?

 Foetal Pole
 Foetal Pole

Around the second month of pregnancy, your doctor may suggest a trans-abdominal or transvaginal ultrasonography procedure. These will help identify developmental changes in the foetus, such as the formation of the foetal pole and detection of the foetal heartbeat.

Missing Foetal Pole: What Now?

Why is the foetal pole not always seen on an ultrasound? There are numerous factors involved in the detection of a healthy foetus, such as the size of the gestational sac, menstrual cycle, measurement error and so on. Here is what a missing foetal pole could mean.

  • Pregnancy Has Been Dated Incorrectly

Since the time scale for the appearance of the foetal pole can range between around six and nine weeks, predicting the time of conception incorrectly by even a few days could create an inaccurate reading of the ultrasound. For example, not correctly remembering your last menstrual period could throw off the predicted dates. Irregular cycles which are not consistently followed by ovulation two weeks after the period could mean that the pregnancy is not as old as you think it is.

  • Pregnancy Has Failed

Sadly, the absence of a foetal pole can often mean that the pregnancy has not worked or that a miscarriage has occurred. In some cases, the uterine sac can develop and grow further for weeks before miscarriage can be identified. Another reason for miscarriage is the presence of a gestational sac larger than twenty-five mm without the foetal pole.

  • If There is a Foetal Pole But No Heartbeat?

When the foetus is around 7 weeks old, its heartbeat is easily detectable. Normal heart rate can be in the range of 100-160 beats per minute. However, if the heartbeat is lower than 90 bpm, then it could be a non-viable pregnancy. Additionally, if the foetal pole can be seen, but the heartbeat is absent, all indications lead to a miscarriage or an ectopic pregnancy. As this is a common scenario, your doctor will most likely ask you to return for a follow-up ultrasound in the upcoming weeks to give the pregnancy enough time to develop. If future scans show similar results your doctor will confirm that a miscarriage has occurred. 

The development of a baby is a rather complex process. While one must always hope for the best, it will be helpful to prepare for difficult situations, so you can be ready. Even in the worst-case scenarios, it is important to remember that you have friends and family to lean on for support. And remember, you can always, always try again.

Also Red; Fetal Heart Rate Change During Pregnancy