Fetal Pole – Role, Disorder and Treatment

Pregnancy typically lasts between thirty-eight to forty weeks, counted from the first day of the last menstruation. These days, pregnancies are easily detectable, usually through blood or urine testing, which can confirm the presence of the hCG hormone as early as ten days after conception. The first physical sign of a foetus, however, will appear in the form of a structure known as the foetal pole, which can be seen on an ultrasound. At this point, the embryo is barely visible as a tiny comma shape, representing the earliest stage of development. Sometimes, the foetal pole might not be visible during an early ultrasound scan, especially if the pregnancy is still in its very early stages, but there is no need to be nervous, as this is often normal.

What Is the Fetal Pole?

The foetal pole will appear in the fifth week of pregnancy as a three to five mm thickening around the margin of the foetal yolk sac, which provides nutrition for the growing embryo. As per the fetal pole definition, it is essentially the structure that becomes the foetus. It has a curved structure, with the head at one end and a tail like formation on the other end. The distance between the head and tail also 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 handy approximation for the age of the foetus. The age is measured by adding the length of the foetus in mm to 6 weeks. For instance, if the foetal pole is six mm long, then its age is six weeks and six days. However, this is only an approximate idea of the age.

Where Is the Fetal Pole Located?

The fetal pole is located within the gestational sac, which is found inside the uterus. The fetal pole typically appears within the gestational sac between five and six weeks of pregnancy and represents the developing embryo. It is often positioned along the edge of the yolk sac, another structure that provides nourishment to the embryo in the early stages of pregnancy. The gestational sac is located in the uterus in a normal pregnancy.

Does a Fetal Pole Mean There’s a Baby?

A fetal pole is an early sign of a developing embryo, but it doesn’t necessarily guarantee a healthy baby will result. The presence of a fetal pole on an ultrasound indicates that the pregnancy is progressing and that an embryo is forming. However, it is still in the very early stages of development.

In most cases, the appearance of a fetal pole is a positive sign that the pregnancy is viable. As the weeks progress, the fetal pole will grow, and other structures like the heartbeat will become visible, which further confirms the health of the pregnancy. However, in some cases, a fetal pole may be seen, but the pregnancy might not continue due to various reasons like developmental issues or miscarriage. Therefore, while the fetal pole is an essential milestone, it is just one of many factors that determine the outcome of the pregnancy.

When Is It Seen on the Ultrasound?

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

What Role Does Fetal Pole Play in Early Pregnancy?

The fetal pole is a crucial indicator in early pregnancy, marking the first visible sign of the developing embryo. Understanding its role can provide reassurance and insight into the progress of a pregnancy.

• The appearance of the fetal pole on an ultrasound confirms that the embryo has begun to form, indicating that the pregnancy is progressing as expected.
• The presence of a fetal pole, along with a heartbeat, typically around six weeks, suggests that the pregnancy is likely viable and developing normally.
• The size of the fetal pole can be measured to help estimate the gestational age of the embryo, which aids in determining the expected due date.
• The detection of a fetal pole within the gestational sac confirms that the pregnancy is located in the uterus, ruling out an ectopic pregnancy.
• Regular ultrasounds to monitor the growth of the fetal pole can help detect any abnormalities or delays in development, allowing for early intervention if necessary.

What Are the Disorders Related to Fetal Pole?

The fetal pole is a critical marker of early pregnancy, but sometimes, its development may not proceed as expected, leading to certain disorders. Understanding these potential issues can help in early diagnosis and management.

• Blighted Ovum: A blighted ovum occurs when a gestational sac develops without a fetal pole or embryo, often leading to a miscarriage in the first trimester.
• Ectopic Pregnancy: Although rare, a fetal pole might appear in an ectopic pregnancy, where the embryo implants outside the uterus, commonly in the fallopian tube, leading to a non-viable pregnancy and potential complications.
• Delayed Fetal Pole Development: Sometimes, the fetal pole’s appearance is delayed beyond the typical timeframe, which might indicate a miscalculation in gestational age or a potential issue with pregnancy viability.
• Pregnancy of Unknown Location (PUL): This condition is defined by a positive pregnancy test without any detectable signs of pregnancy within or outside the uterus. It is generally considered a preliminary diagnosis, pending further investigation.
• Fetal Growth Restriction (FGR): This condition arises when the fetus is smaller than expected for its gestational age, meaning it isn’t growing at the typical rate during pregnancy. A missed miscarriage is identified when a fetal pole is present without a heartbeat, especially if the crown-rump length exceeds 7 millimeters. In this case, the embryo has either ceased to develop or has died, but the body hasn’t expelled it.

Missing Fetal Pole: Is It a Concern?

Why is the foetal pole not seen sometimes on an ultrasound? There are several 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 an absent foetal pole could mean.

1. The Pregnancy Has Been Dated Incorrectly

Since the timescale for the appearance of the foetal pole can range between six and nine weeks, predicting the time of conception incorrectly by even a few days could create an inaccurate reading of the ultrasound. For instance, misremembering your last menstrual period could throw off the predicted dates. Also, 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.

2. The Pregnancy Has Failed

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

What If There Is a Fetal Pole But No Heartbeat?

What if there’s a foetal pole but no heartbeat? When the foetus is around seven weeks old, its heartbeat is detectable. Normal heart rate will be in the range of 100-160 beats per minute. However, if the heartbeat is anything lower than 90 bpm, then it could be a non-viable pregnancy. Further, if the foetal pole can be seen, but the heartbeat is absent, all indications lead to a miscarriage or an ectopic pregnancy.

Tests to Check Fetal Pole Growth

Monitoring the growth of the fetal pole is essential in assessing the progress and health of an early pregnancy. Several tests and procedures can help track and evaluate the development of the fetal pole.

• Ultrasound Imaging: The most effective method for diagnosing Fetal Growth Restriction (FGR) is through ultrasonography, which estimates the fetal weight. Ultrasound uses sound waves to create images of the unborn child within the womb, ensuring both the mother and baby remain unharmed.
• Doppler Ultrasound: This test measures the blood flow from the placenta to the baby through the umbilical cord. A reduction in blood flow may indicate the presence of FGR, signaling that the baby is not receiving enough nutrients.
• Fetal Echocardiogram: This specialized ultrasound focuses on the fetal heart and may be recommended in high-risk pregnancies or when an anomaly is detected during a routine ultrasound, potentially indicating a cardiac issue.
• Fetal MRI: A fetal MRI might be suggested when there is a suspicion of birth defects, particularly those affecting the brain or nervous system, offering detailed images that complement ultrasound findings.
• Maternal Blood Screening: Blood tests can measure protein levels and circulating free fetal DNA in the mother’s blood. Abnormal results could indicate a higher likelihood of fetal chromosomal abnormalities.
• Maternal Serum Screening: Conducted during the second trimester, this blood test can detect chromosomal abnormalities and conditions like spina bifida, providing crucial information about the baby’s health.
• Serum Alpha-Fetoprotein (AFP): This diagnostic tool is particularly useful for detecting yolk sac tumors and, when combined with amniocentesis, can help identify genetic causes of Intrauterine Growth Restriction (IUGR) or assess fetal lung maturity.

Treatments of Fetal Pole

When issues with the fetal pole are detected during early pregnancy, certain treatments and interventions may be recommended to support the pregnancy or address potential complications. These treatments aim to promote healthy development and manage any identified concerns.

• Dilation and Curettage (D&C): This surgical procedure involves removing placental tissue from the uterus. The cervix is opened, and surgical instruments, along with suction, are used to extract the pregnancy tissues. This procedure is performed under general anesthesia.
• Salpingostomy: In this surgical procedure, an ectopic pregnancy is removed while preserving the fallopian tube, which is allowed to heal naturally. It involves carefully removing the ectopic tissue and allowing the tube to recover on its own.
• Chemotherapy: Typically, patients undergo at least three rounds of chemotherapy. The effectiveness of the treatment is often monitored by checking whether tumor markers decrease after each session.

Medicines for Fetal Pole

When issues with the fetal pole are identified, certain medications may be prescribed to address underlying concerns and support the pregnancy. These medications aim to enhance the chances of a healthy outcome by managing specific aspects of early pregnancy.

• HCG Therapy: This is a commonly used hormonal treatment for addressing pregnancies of unknown location (PUL). It involves either a single serum hCG test or a series of hCG measurements to assess and predict the outcome of the pregnancy.
• Oral Medications with Surgical Intervention: For managing anembryonic pregnancies, combining oral medications like misoprostol with surgical procedures is believed to be more effective. For managing anembryonic pregnancies, combining oral medications like misoprostol with surgical procedures is believed to be more effective.

Tips to Keep Fetal Pole Healthy and Viable

Maintaining the health and viability of the fetal pole is crucial for a successful early pregnancy. Implementing certain practices can help support the development of the fetal pole and contribute to a healthy pregnancy.

• Schedule and attend regular prenatal appointments to monitor the growth and development of the fetal pole and overall pregnancy health.
• Consume a well-balanced diet rich in essential nutrients, including folic acid, iron, and calcium, to support fetal development and maternal health.
• Drink plenty of water to stay hydrated, which is important for maintaining optimal amniotic fluid levels and supporting fetal growth.
• Steer clear of alcohol, tobacco, and recreational drugs, as these can negatively impact fetal development and increase the risk of complications.
• Practice stress-reducing techniques such as meditation, yoga, or deep breathing to promote a healthy environment for fetal development.
• Ensure you get enough sleep and rest to support your body’s increased demands during pregnancy and contribute to overall fetal health.
• Use prenatal vitamins as prescribed by your healthcare provider to ensure you are getting the necessary vitamins and minerals for fetal development.
• Maintain a healthy weight gain during pregnancy as recommended by your healthcare provider to support fetal growth and reduce the risk of complications.
• Refrain from high-risk activities and exercises that could potentially harm the pregnancy or the developing fetal pole.

FAQs

1. Can the fetal pole develop abnormalities that are not immediately visible on an early ultrasound?

Yes, some abnormalities of the fetal pole, such as structural issues or growth restrictions, may not be immediately visible on an early ultrasound. These issues might become more apparent as the pregnancy progresses or require specialized imaging for diagnosis.

2. How might a low maternal thyroid hormone level affect the development of the fetal pole?

Low levels of maternal thyroid hormones (hypothyroidism) can impact fetal development, including the growth of the fetal pole. Thyroid imbalances may lead to developmental delays or complications, so it’s important to manage thyroid levels during pregnancy.

3. Can the fetal pole’s growth be affected by maternal autoimmune disorders?

Yes, autoimmune disorders such as lupus or antiphospholipid syndrome can potentially affect fetal development, including the growth of the fetal pole. These conditions may impact blood flow to the placenta or increase the risk of pregnancy complications.

4. What impact does exposure to certain medications have on the fetal pole during early pregnancy?

Certain medications, particularly those not recommended during pregnancy, can influence the development of the fetal pole. Medications with known teratogenic effects or those that impact hormone levels may alter fetal pole growth or viability. Always consult with a healthcare provider about medication use during pregnancy.

As this is a rather common scenario, your doctor will most likely ask you to return for a follow-up ultrasound in the next couple of weeks to give the pregnancy enough time to develop. Only if future scans show similar results will your doctor confirm that a miscarriage has occurred. The development of a baby is a very complex procedure. While one must always hope for the best, it helps to prepare for difficult situations, so you can be ready. Even in this worst-case scenario, it is important to remember that you have friends and family to lean on for support. And remember, you can always try again.

References/Resources:

1. Fetal Pole; Cleveland Clinic; https://my.clevelandclinic.org/health/body/22546-fetal-pole

2. Methods for Estimating the Due Date; American College of Obstetricians and Gynecologists Clinical; https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date

3. Murugan. V, Murphy. B, Dupuis. C, Goldstein. A, Kim. Y; Role of ultrasound in the evaluation of first-trimester pregnancies in the acute setting; Ultrasonography; https://www.e-ultrasonography.org/journal/view.php?doi=10.14366/usg.19043; October 2019

4. Chaudhry. K, Tafti. D, Carlson. K, Siccardi. M; Anembryonic Pregnancy; National Library of Medicine; https://www.ncbi.nlm.nih.gov/books/NBK499938/

5. Yolk Sac; Cleveland Clinic; https://my.clevelandclinic.org/health/body/22341-yolk-sac

Also Read:

Foetal Movement
Foetal Monitoring
Stages of Foetal Lung Development
Foetal Growth Chart Week by Week

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