فتال مانیتورینگ یا جنین یاب دستگاهی جهت تشخیص صدای قلب جنین و محاسبه تعداد ضربان قلب است.این دستگاه بر اساس تئوری داپلر با استفاده از سیستم مافوق صوت و از طریق پروب تبدیل کننده،صدای قلب جنین را منعکس می کند که از طریق بلندگو یا گوشی قابل شنیدن است و هیچ گونه خطری از لحاظ اشعه و امواج الکتریکی یا الکترو مغناطیس ایجاد نمی کند.دستگاه جنین یاب که فتال داپلر یا سونی کید نیز نامیده می شود.
نحوه عملکرد دستگاه جنین یاب
در این دستگاه،مبدل فرستنده به یک نوسانگر متصل شده و به طور پیوسته امواج ماوراء صوت رابه طرف جنین ارسال می کند. این امواج پس از برخورد با جنین و بازگشت، از طریق مبدل گیرنده که در همان پروب قرار گرفته دریافت شده و به سیگنال الکتریکی تبدیل می شود.
فرکانس موج بازگشتی برابر با فرکانس موج تابش شده است اما حرکت قبل جنین تغییر می کند که متناسب با سرعت ضربان قلب است.انتخاب فرکانس بهینه برای سیستم با توجه به دو موضوع انجام می شود:
۱-برای نفوذ خوب و بدون جذب زیاد، یک فرکانس کم بهترین انتخاب است زیرا تضعیف در بافت ها به صورت غیر خطی با افزایش فرکانس افزایش می یابد.
۲-به منظورافزایش توان برگشتی حاصل از مجموعه و هم چنین دقت بالاتر، فرکانس بالاتر متناسب تر است،زیرا باعث می شود که هر سلول با مقدار بیشتری از سیگنال های ارسالی برخورد داشته باشد.
Fetal heart rate monitoring measures the heart rate and rhythm of your baby (fetus). This lets your healthcare provider see how your baby is doing.
Your healthcare provider may do fetal heart monitoring during late pregnancy and labor. The average fetal heart rate is between 110 and 160 beats per minute. It can vary by 5 to 25 beats per minute. The fetal heart rate may change as your baby responds to conditions in your uterus. An abnormal fetal heart rate may mean that your baby is not getting enough oxygen or that there are other problems.
There are 2 ways to do fetal heart monitoring, external and internal:
External fetal heart monitoring
This method uses a device to listen to and record your baby’s heartbeat through your belly (abdomen). One type of monitor is a Doppler ultrasound device. It’s often used during prenatal visits to count the baby’s heart rate. It may also be used to check the fetal heart rate during labor. The healthcare provider may also check your baby’s heart rate continuously during labor and birth.
To do this, the ultrasound probe (transducer) is fastened to your belly. It sends the sounds of your baby’s heart to a computer. The rate and pattern of your baby’s heart rate are shown on a screen and printed on paper.
Internal fetal heart monitoring
This method uses a thin wire (electrode) put on your baby’s scalp. The wire runs from the baby through your cervix. It is connected to the monitor. This method gives better readings because things like movement don’t affect it. But it can only be done if the fluid-filled sac that surrounds the baby during pregnancy (amniotic sac) has broken and the cervix is opened.
Your provider may use internal monitoring when external monitoring is not giving a good reading. Or your provider may use this method to watch your baby more closely during labor.
During labor, your healthcare provider will watch your uterine contractions and your baby’s heart rate. Your provider will note how often you are having contractions and how long each lasts. Because the fetal heart rate and contractions are recorded at the same time, these results can be looked at together and compared.
Your provider may check the pressure inside your uterus while doing internal fetal heart monitoring. To do this, he or she will put a thin tube (catheter) through your cervix and into your uterus. The catheter will send uterine pressure readings to a monitor.
Why might I need fetal heart monitoring?
Fetal heart rate monitoring is especially helpful if you have a high-risk pregnancy. Your pregnancy is high risk if you have diabetes or high blood pressure. It is also high risk if your baby is not developing or growing as it should.
Fetal heart rate monitoring may be used to check how preterm labor medicines are affecting your baby. These are medicines are used to help keep labor from starting too early.
Fetal heart rate monitoring may be used in other tests, including:
Nonstress test. This measures the fetal heart rate as your baby moves.
Contraction stress test. This measures fetal heart rate along with uterine contractions. Contractions are started with medicine or other methods.
A biophysical profile (BPP). This test combines a nonstress test with ultrasound.
Things that may affect the fetal heart rate during labor:
Pain medicines or anesthesia given to you during labor
Tests done during labor
Pushing during the second stage of labor
Your healthcare provider may have other reasons to use fetal heart rate monitoring.
What are the risks of fetal heart monitoring?
Radiation is not used for this test. The transducer usually causes no discomfort.
You may find the elastic belts that hold the transducers in place slightly uncomfortable. These can be readjusted as needed.
You must lie still during some types of fetal heart rate monitoring. You may need to stay in bed during labor.
With internal monitoring, you may have some slight discomfort when the electrode is put in your uterus.
Risks of internal monitoring include infection and bruising of your baby’s scalp or other body part.
Note: You should not have internal fetal heart rate monitoring if you are HIV positive. This is because you may pass the infection on to your baby.
You may have other risks depending on your specific health condition. Be sure to talk with your provider about any concerns you have before the procedure.
Certain things may make the results of fetal heart rate monitoring less accurate. These include:
Obesity of the mother
Position of the baby or mother
Too much amniotic fluid (polyhydramnios)
Cervix is not dilated or the amniotic sac is not broken. Both of these need to happen to do internal monitoring
How do I get ready for fetal heart monitoring?
Your healthcare provider will explain the procedure to you. Ask him or her any questions you have about the procedure.
You may be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if anything is not clear.
The consent form for fetal heart monitoring may be included as part of the general consent for labor and birth.
Tell your healthcare provider if you are sensitive to or are allergic to any medicines, latex, tape, or anesthesia.
If fetal heart rate monitoring is done along with another monitoring test, you may be asked to eat a meal before the test. This can help make your baby more active.
The amniotic sac must be broken and your cervix must be dilated several centimeters before the internal device can be put in place.
Follow any other instructions your provider gives you to get ready.
What happens during fetal heart monitoring?
You may have fetal heart rate monitoring in your healthcare provider’s office or as part of a hospital stay. The way the test is done may vary depending on your condition and your healthcare provider’s practices.
Generally, fetal heart rate monitoring follows this process:
External fetal heart monitoring ( Fetal Manitoring )
Depending on the type of procedure, you may be asked to undress from the waist down. Or you may need to remove all of your clothes and wear a hospital gown.
You will lie on your back on an exam table.
The healthcare provider will put a clear gel on your abdomen.
The provider will press the transducer against your skin. The provider will move it around until he or she finds the fetal heartbeat. You will be able to hear the sound of the fetal heart rate with Doppler or an electronic monitor.
During labor, the provider may check the fetal heart rate at intervals or nonstop, based on your condition and the condition of your baby.
For continuous electronic monitoring, the provider will connect the transducer to the monitor with a cable. A wide elastic belt will be put around you to hold the transducer in place.
The provider will record the fetal heart rate. With continuous monitoring, the fetal heart pattern will be displayed on a computer screen and printed on paper.
You may not be able to get out of bed with nonstop external fetal heart rate monitoring.
Once the procedure is done, the provider will wipe off the gel.
Internal fetal heart monitoring
You will be asked to remove your clothes and put on a hospital gown.
You will lie on a labor bed. Your feet and legs will be supported as for a pelvic exam.
Your healthcare provider will do a vaginal exam with a gloved hand to see how far you are dilated. This may be slightly uncomfortable.
If the amniotic sac is still intact, your healthcare provider may break open the membranes with a tool. You will feel warm fluid coming out of your vagina.
Your healthcare provider will feel the part of the baby at the cervical opening with gloved fingers. This is usually the baby’s head.
The provider will put a thin tube (catheter) into your vagina. He or she will put a small wire at the end of the catheter on the baby’s scalp. He or she will gently turn it on the baby’s skin.
The provider will remove the catheter and leave the wire in place on the baby’s scalp.
The provider will connect the wire to a monitor cable. He or she will keep it in place with a band around your thigh.
You may not be able to get out of bed with nonstop internal fetal heart rate monitoring.
Once the baby is born, the provider will remove the wire.
What happens after fetal heart rate monitoring?
You do not need any special care after external fetal heart monitoring. You may go back to your normal diet and activity unless your healthcare provider tells you otherwise.
After internal fetal heart rate monitoring, your healthcare provider will check your baby’s scalp for infection, bruising, or a cut. The provider will clean the site with an antiseptic.
Your healthcare provider may give you other instructions, based on your situation.
Before you agree to the test or the procedure make sure you know:
The name of the test or procedure
The reason you are having the test or procedure
What results to expect and what they mean
The risks and benefits of the test or procedure
What the possible side effects or complications are
When and where you are to have the test or procedure
Who will do the test or procedure and what that person’s qualifications are
What would happen if you did not have the test or procedure
Any alternative tests or procedures to think about
When and how will you get the results
Who to call after the test or procedure if you have questions or problems
How much will you have to pay for the test or procedure