Monitoring your baby’s heart rate in labour
This article has been written to explain how your midwife and doctor observe and record your baby’s heart rate during labour, so they can monitor your baby’s health and wellbeing.
During your pregnancy, the midwives and doctors will regularly listen into your baby’s heartbeat. They do this to check that there are no changes to your baby’s heart rate pattern, which could suggest your baby has a problem with their health and wellbeing. A baby’s normal heart rate can be anything in the range 110 to160 beats per minute and this rate changes constantly. Your midwife and doctor will describe this constant change in your baby’s heart rate as the ‘beat-to-beat variation’ or ‘variability’. A sign that your baby is healthy is where there is a beat-to-beat variation of at least five beats per minute and where your baby’s heartbeat speeds up when they move inside the uterus (womb), or where they are stimulated eg during an abdominal palpation (where your midwife feels your abdomen to determine the position of your baby), or during a vaginal examination where the baby’s head is touched. Where your baby’s heartbeat speeds up these are called ‘fetal heart accelerations’.
Why will the midwives ask to monitor my baby’s heart rate in labour?
Labour and birth is probably the most stressful episode of any baby’s young life. This is because with every labour contraction, the blood flow to the placenta (afterbirth) is temporarily diminished and this reduces your baby’s oxygen supply. This causes hypoxia (diminished oxygen supply to the body tissues) for a short period of time; however, this should resolve swiftly once your uterine contraction has subsided. Do not be alarmed by the term hypoxia, as a baby’s metabolism is designed to cope with this in active labour. When your midwife listens to your baby’s heartbeat during a strong contraction, they may hear a general slowing down of the baby’s heart rate which then returns to its normal rate once the contraction has ended. This is normal.
The majority of babies cope with labour contractions and birth without any difficulty. However, if your baby is smaller than average or you go into labour prematurely (too early); you experience a long labour or your uterine contractions are particularly strong and/or too close together (with very little break between them), this can have a significant impact on your baby’s oxygen supply. This then results in your baby’s oxygen levels being reduced further which can cause their health and wellbeing to become compromised. If your baby is struggling to cope with labour contractions this will often be detected by changes to the rate and pattern of their heartbeat – this is called fetal distress.
How might they monitor my baby’s heart rate?
There have been many advances in fetal monitoring during labour. The methods of monitoring advised by your midwife and doctor will be influenced by the nature of your pregnancy and labour. Where you have had an uncomplicated (straightforward) pregnancy and labour your midwife may listen into your baby’s heart rate at intervals using a Pinard stethoscope – this is also commonly called the midwife’s stethoscope. Alternatively, they may use a small handheld electronic device called a Doppler (Doptone). This has a small handheld transducer which, when placed against the skin of your abdomen, allows you and your midwife to hear your baby’s heartbeat. Your midwife will count your baby’s heart rate; in just the same way as when you are having your pulse checked. Hand-held Dopplers are often used by midwives when assisting at homebirths and waterbirths. In some areas they are also available for expectant parents to hire or purchase.
If you have a more complex pregnancy or there is an underlying health condition which might mean your baby could struggle to cope with labour, your midwife will recommend that your baby is monitored more closely. For example, where your membranes have ruptured for more than 24 hours before labour begins; where your baby is small (called small for dates), or your baby is post-mature (overdue). Where this is indicated, your baby’s heartbeat can be continuously monitored using a cardiotocograph (CTG). A CTG is an electronic fetal heart rate monitor that records your baby’s heart rate and pattern alongside the frequency of your uterine contractions.
This next section will look in more detail at the different methods that can be used to monitor a baby’s heart rate.
Listening intermittently using a Pinard stethoscope or hand-held Doptone
Intermittent auscultation (listening) of a baby’s heart rate is undertaken where a woman’s pregnancy and labour are straightforward and uncomplicated. During the first stage of labour – when your cervix (neck of the womb) is dilating, your baby’s heart rate will be listened to for one full minute after each contraction and this will be done at 15 minute intervals. When you are in the second stage of labour (when you are pushing); your baby’s heart rate will be listened to for one full minute at five minute intervals. The midwife caring for you in labour will always check your pulse rate at the same time as listening to your baby’s heartbeat. This is because your major blood vessel – the aorta lies very close to your uterus, which can cause confusion between yours and your baby’s heartbeats. Differentiation between your pulse rate and your baby’s ensures that any concerns about your baby’s wellbeing are detected early and can be acted upon. Checking your pulse is also a routine aspect of labour care and a means of monitoring your health and wellbeing too. Should your midwife or doctor detect a potential concern, or the nature of your pregnancy and labour means that your baby needs to be monitored more closely; they will always recommend electronic fetal monitoring (EFM).
Electronic fetal heart rate monitoring
EFM means that your baby’s heart rate pattern is recorded using a CTG machine; this provides an audible recording of your baby’s heartbeat as well as a paper printout. The top recording is your baby’s heart rate which changes all the time and will show as a ‘jagged’ pattern with ‘peaks’ where your baby’s heartbeat accelerates. The recording at the bottom of the page shows uterine activity ie contractions – when you are in established labour your uterine contractions are recorded as ‘waves’. They enable the midwives and doctors to see how often you are contracting within a 10 minute period. The CTG print out also informs the doctors and midwives how well your baby is coping with the contractions. However, your midwife will also feel your abdomen to gauge the strength and duration of your contractions. CTGs also have a volume control, which can be increased if the midwives and doctors, or you and your partner want or need to listen to your baby’s heartbeat
Your baby’s heart rate and pattern is picked up via two transducers (small electronic discs) which are placed against the skin of your abdomen and held in place with two elastic belts. These belts can be adjusted to hold the transducers in place while ensuring that they are comfortable to wear. One transducer is placed on the fundus (ie the very top of the uterus) and the other is positioned close to your baby’s heartbeat. Where your baby is cephalic (lying head down); the transducer will be placed on your lower abdomen. However, if your baby is breech (bottom first); the transducer will be placed higher up. A clear gel is placed on the surface of the transducer which records your baby’s heart rate; this ensures that the electronic signal is picked up clearly. Each transducer is attached by a lead to the CTG machine.
When EFM was first introduced back in the 197Os, it was assumed that its use would make labour and birth safer for babies. However, research studies have since shown that the routine use of EFM, particularly where it is used inappropriately – even for a short time (eg low risk births) or is used too much, is associated with more babies being born by caesarean section. Research has also found that the use of EFM can interfere with women’s choice of pain relief during labour – eg TENS and EFM are contraindicated when choosing immersion in water. Studies have also found that continuous monitoring can restrict women’s movements/mobility and their adopting different positions for labour and birth. Some maternity units now offer telemetry which provides wireless EFM. This means that women can be monitored without any restrictions on their mobility or choice of positions, and also enables them to use water for labour and/or birth.
Fetal scalp electrode
A fetal scalp electrode (FSE) will be recommended if there are difficulties picking up your baby’s heartbeat abdominally. They are often used with twin pregnancies when it is important that the fetal heartbeats of Twin I and Twin II are differentiated between, as well as, with women who are significantly overweight. The FSE is a small clip attachment that is fixed onto the scalp (top) of your baby’s head during a vaginal examination. Your membranes (the waters) need to have been ruptured (broken) before this can be done. Because the FSE is in direct contact with the baby it enables the midwives and doctors to obtain a far more accurate recording of your baby’s heart rate and pattern. It also means that your baby’s heartbeat can be more easily monitored throughout both the first stage and second stages of labour. In the second stage of labour it can be more difficult to pick up the baby’s heartbeat because they are passing down through the pelvis and birth passage (vagina).
Fetal blood sampling
Fetal blood sampling (FBS) is used in conjunction with continuous EFM and is only undertaken where there are significant concerns about how your baby is coping with labour. The CTG can give doctors and midwives a certain amount of information, but cannot conclusively determine if the baby is truly distressed and being starved of oxygen. To accurately assess your baby’s condition, the doctor will take a tiny amount of blood from the scalp of your baby’s head in order to see how much oxygen is present or to measure lactate (high lactate indicates fetal distress). The doctor can also measure how high the acid level (Ph) is in your baby’s blood; this is known as the ‘base excess’. Where the oxygen level is low and the acid level is high this gives a good indication of how ‘distressed’ your baby is. These tests are performed during a vaginal examination and your membranes need to have ruptured.
In order to clearly visualise the top of your baby’s head, your midwife and doctor may ask you to lie on your left side with your upper leg raised and supported, or with your legs in the lithotomy poles. A vaginal examination is performed and a small cone-like instrument is gently inserted so that the narrowest part of the cylinder rests closely against the top of your baby’s head. A tiny little cut is then made in the baby’s scalp and the blood is collected into a very fine (tiny) glass tube called a capillary tube. A special machine then extracts the blood from the tube and measures the oxygen and carbon dioxide/lactate levels present.
The FBS sample can be checked straight away and the results are available within minutes; this means the doctors and midwives will quickly know just how well your baby is coping. The results will also help them to plan your ongoing labour care. Where the FBS shows that your baby is receiving good amounts of oxygen and they are expected to be born quite soon, an FBS may only be taken once. In other cases however, the doctors may recommend repeating the FBS at 30 minute intervals (usually to a maximum of three times) to monitor any changes to your baby’s health. Where the FBS results show that your baby is not coping with labour the doctors may recommend that they are born without delay. If you are fully dilated, the doctors will help you to deliver your baby using forceps or the ventouse. If your cervix has not dilated sufficiently, a caesarean section may be required.
Having an FBS in labour can be an understandably stressful and uncomfortable experience and the midwives and doctors caring for you will be very sympathetic to this. Therefore, they will only ever recommend performing an FBS where there are significant concerns about your baby’s wellbeing. On some occasions, the Delivery Suite staff may advise that you consider having an epidural for pain relief in labour. This is particularly the case, where circumstances indicate that it is likely to be a longer labour; where your baby is going to need to be monitored continuously, or there are concerns that your baby is already compromised (eg they are small; premature; in the breech position) and more likely to struggle with labour contractions.
Other methods of fetal monitoring
Your baby’s heartbeat can be recorded using other methods of electronic fetal heart rate monitoring and we have included a brief description of these below. However, it is important to point out that these methods are more specialised and are currently only used by a very small number of UK maternity units. We felt it was important to include them however, should you hear reference made to them during your pregnancy and labour care.
Whereas EFM looks at the rate and pattern of your baby’s heartbeat; a fetal electrocardiogram (FECG) displays the exact waves that are present in every individual heartbeat. Studies show that FECG serves as a reliable method for electronic fetal monitoring during complicated (high-risk) labours. In order to perform a FECG, a fetal scalp electrode needs to be applied to your baby’s head and your membranes need to have ruptured. Research suggests that when FECG is used alongside EFM this results in fewer fetal blood sampling tests; babies being born in a healthier condition (not requiring transfer to a Neonatal Unit) and fewer births by caesarean section, as opposed to using EFM only. However, more research is needed in this area.
Fetal pulse oximetry
This is another method of monitoring the baby’s heart rate which is used to a much lesser extent than those previously discussed. Fetal pulse oximetry (FPO) requires a probe to be inserted into the vagina so that it lies alongside the baby’s head. The probe measures the amount of oxygen the baby is receiving and also assesses whether they are coping with the uterine contractions. FPO is only used in a very small number of maternity units and more research is needed into its use. However, studies to date suggest that the use of FPO in labour could result in fewer births by caesarean section.
During your pregnancy, your midwife will discuss the various methods of fetal heart rate monitoring in labour as part of your local birth preparation sessions (Parentcraft). They will also talk about the benefits, disadvantages and alternative options associated with each. Once your labour has begun your midwife and, if you are giving birth in hospital, a doctor will explain which method of fetal heart monitoring is the most appropriate for your baby. Labour is a journey and as it progresses circumstance may change which necessitate the midwives and doctors monitoring your baby’s heartbeat more closely. Midwives and doctors will only advise continuous monitoring of the fetal heart rate when there is a clinical indication to do so. Where there are any concerns about your baby’s wellbeing, these will be explained to you throughout. Similarly, if you have any queries or concerns, you should always talk these through with your midwife and/or doctor. It is your body, your baby and your birth, so the midwives and doctors will want to ensure that you are involved and understand your labour care choices and decisions.
Midwives and doctors attend regular skills drills training on electronic fetal heart rate monitoring and the effective interpretation of CTG traces. Many units also include a ‘fresh eyes’ approach to EFM where your midwife may ask their colleague(s) to review your CTG trace – this helps to ensure consistently accurate interpretation of your baby’s heart rate pattern.