1. Assessment Of Fetal Wellbeing In labour
Dr Shaimaa Kadhim AL-Khafajy

2. The objective of fetal monitoring during labour is the prediction and diagnosis of fetal asphyxia before fetal/newborn morbidity with particular reference to brain damage has occurred.

3. Fetal asphyxia is defined as ‘a condition of impaired blood gas exchange leading, if it persists, to progressive hypoxemia and hypercapnia’ . Hypoxemia and hypercapnia as an event during labour may occur in a transient fashion with physiological but no pathological significance.

4. Fetal asphyxia of pathological significance during labour requires progressive hypoxemia with a significant metabolic acidosis.
Thus the diagnosis of fetal asphyxia requires a blood gas and acid–base assessment. In respect to intrapartum fetal asphyxia, the threshold at delivery beyond which cerebral dysfunction or brain damage may occur is an umbilical artery base deficit greater than 12 mmol/l.

5. Prevalence of intrapartum fetal asphyxia
Rate per 1000 live births
Fetal asphyxia
Preterm
Term
Prevalence 73 25
Mild 38 21
Moderate/severe 35 4

6. Fetal assessment in labour
A healthy term fetus is usually able to withstand the normal labour. However, with each contraction, placental blood flow and oxygen transfer are temporarily interrupted and a fetus that is already compromised before labour will become increasingly so.

7. Insufficient oxygen delivery to the fetus causes a switch to anaerobic metabolism and results in the generation of lactic acid and hydrogen ions. In excess, these saturate the buffering systems of the fetus and cause a metabolic acidosis which, in the extreme, can cause neuronal damage and permanent neurological injury, even intrapartum fetal death.

8. Hypoxia and acidosis cause a characteristic change in the fetal heart rate pattern, which can be detected by ausculatation and the cardiotocograph (CTG). Meconium is often passed by a healthy fetus at or after term as a result of maturation of gastrointestinal physiology; in this scenario, it is usually thin and a very dark green or brown colour.

9. It may also be expelled from a fetus exposed to marked intrauterine hypoxia or acidosis; in this scenario, it is often thicker and much brighter green in colour.

10. Fetal assessment in labour takes four forms:
observation of the colour of the liquor – fresh meconium staining and heavy bleeding are markers of potential fetal compromise
intermittent auscultation of the fetal heart using a Pinard stethoscope or a hand-held Doppler ultrasound,

11. continuous external fetal monitoring (EFM) using CTG,
fetal scalp blood sampling (FBS).

12. The fetal heart rate (FHR) should be auscultated, early in the initial assessment. It should be listened to for at least a minute,immediately after a contraction.

13. This should be repeated every 15 minutes during first stage, and at least every 5 minutes in second stage.A CTG should be performed if there are issues which might complicate labour and delivery.

14. Most of these women will also be advised to have continuous electronic fetal monitoring (EFM) throughout labour, using the CTG.

15. Women who begin labour with intermittent auscultation may be advised to change to continuous EFM if any of the following events occur during their labour:
significant meconium staining to the liquor;
abnormal fetal heart rate detected by intermittent auscultation;
maternal pyrexia;
fresh vaginal bleeding;
augmentation of contractions with oxytocin;
at the request of the woman.

16. The quality of a CTG recording is sometimes poor because of fetal position or maternal obesity. A fetal scalp electrode may overcome this problem. It is fixed into the skin of the fetal scalp and picks up the fetal heart rate directly. It rarely causes any harm to the fetus but requires a certain degree of cervical dilatation to be fitted, and for the membranes to be ruptured if they have remained intact.

18. In brief, features of a normal fetal heart rate pattern include a baseline rate of between 110 and 160 bpm (beats per minute), a baseline variability of between 5 and 25 bpm, and the absence of decelerations. Interpreting the CTG in labour is somewhat different to that of an antenatal CTG, particularly in second stage.

19. The absence of accelerations is of uncertain significance during labour, and the presence of simple variable decelarations, or early decelerations, later on in labour is extremely common and not usually a sign of significant fetal compromise.

20. Each feature of the CTG (baseline rate, variability, decelerations and accelerations) should be assessed each time a CTG is reviewed. Each feature can be described as ‘reassuring’, ‘non-reassuring’ or ‘abnormal’

21. Any reversible causes must be considered and addressed and further assessment of the fetus made with fetal blood sampling. If this is not possible or safe then the baby should be delivered without delay.

22. If all four features are reassuring then the CTG is considered ‘normal’. If one feature is non-reassuring (and the other three are reassuring) then the CTG is described as ‘suspicious’. If there are two or more non-reassuring features, or any abnormal features, then the CTG is ‘pathological’.

23. Unfortunately, the CTG can be difficult to interpret and it carries a significant false-positive rate, i.e. it often raises the possibility of fetal compromise when in truth the fetus is still in good condition.

24. In order that the use of the CTG does not lead to unnecessary intervention, a fetal blood sampling may be performed during labour to measure fetal pH .

28. Fetal compromise in labour
Concern for the well-being of the fetus is one of the most common reasons for medical intervention during labour. The fetus may already be compromised before labour, and the reduction in placental blood flow associated with contractions may uncover this and ultimately lead to fetal hypoxia and eventually acidosis. Fetal compromise may present as fresh meconium staining to the amniotic fluid, or an abnormal CTG.

29. However, neither of these findings confirms fetal hypoxia or acidosis
However, neither of these findings confirms fetal hypoxia or acidosis. Meconium can be passed for benign reasons, such as fetal maturity, and it is well recognized that the abnormal CTG carries a very high false-positive rate for the diagnosis of fetal compromise.

30. Intervention for ‘presumed fetal compromise’ is
therefore more accurate than ‘fetal distress’. In many cases, babies delivered by Caesarean section or instrumental birth for presumed fetal compromise are found to be in good condition.

31. Risk factors for fetal compromise in labour
Placental insufficiency – intrauterine growth restriction (IUGR) and pre-eclampsia
Prematurity
Postmaturity
Multiple pregnancy
Prolonged labour
Augmentation with oxytocin

32. Uterine hyperstimulation
Precipitate labour
Intrapartum abruption
Cord prolapse
Uterine rupture/dehiscence
Maternal diabetes

33. Cholestasis of pregnancy
Maternal pyrexia
Chorioamnionitis
Oligohydramnios

34. Recognition of fetal compromise
Meconium staining of the amniotic fluid is considered significant when it is either thick or tenacious,dark green, bright green or black. Thin and light meconium is more likely to represent fetal gut maturity than fetal compromise.

35. CTG signs suggestive of fetal compromise
Fetal tachycardia (>160 bpm, or a steady rise over the course of the labour)
Loss of baseline variability (<5 bpm)
Recurrent late decelerations
Persistent variable decelerations
Fetal bradycardia (<100 bpm for more than 3 minutes)

36. Management of possible fetal compromise
A number of resuscitative manoeuvres should be considered when a CTG is classified as ‘suspicious’. It is reasonable to continue observation of the CTG and more complex intervention is not required. If a CTG becomes ‘pathological’, these reversible factors should also be considered, but it is also important to carry out an immediate vaginal examination to exclude malpresentation and cord prolapse and to assess the progress of the labour.

37. If the cervix is fully dilated, it may be possible to deliver the baby vaginally using the forceps or ventouse. Alternatively, if the cervix is not fully dilated, a fetal blood sampling can be considered. This is usually only possible when the cervix is dilated 3 cm or more.

38. A normal result will permit labour to continue, although it may need to be repeated every 30–60 minutes if the CTG abnormalities persist or worsen. An abnormal result mandates immediate delivery, by Caesarean section if the cervix is not fully dilated.

39. Fresh, thick meconium in the presence of a reassuring CTG is still a cause for concern, and although the labour should be allowed to continue, the threshold for intervention will be lowered and a paediatrician should be present at delivery.

40. Resuscitating the fetus in labour
Maternal dehydration and ketosis can be corrected with intravenous fluids.
Maternal hypotension secondary to an epidural can be reversed by a fluid bolus, although a vasoconstrictor such as ephedrine is occasionally necessary.

41. Uterine hyperstimulation from excess oxytocin can be treated by turning off the infusion temporarily and using tocolytic drugs, such as terbutaline.
Venocaval compression and reduced uterine blood flow can be eased by turning the woman into a left lateral position.

42. Fetal blood sampling
Explanation is given and consent obtained from the woman. She is asked to lie in the left lateral position.
An amnioscope is inserted into the vagina and its distal end is placed at right angles on to the fetal head. The scalp is cleaned and a small cut is made using a blade with a guard. The resulting blood is collected into a microtube. The amount of blood required is approximately 0.25 mL.

45. A normal pH value is above 7. 25. A pH below 7
A normal pH value is above A pH below 7.20 is confirmation of fetal compromise. Values between 7.20 and 7.25 are ‘borderline’.
The base deficit can also be useful in interpretation of the fetal scalp pH. A base excess of more than 􏰀10 demonstrates a significant metabolic acidosis, with increasing risk of fetal neurological injury beyond this level.

46. More than one fetal scalp sample may be necessary over the course of the labour. A downward trend in the fetal scalp pH values is to be expected and should be assessed together with how the labour is progressing.

47. If an abnormal CTG persists in labour, then, despite normal values, fetal scalp sampling should be repeated every 60 minutes, or sooner if the CTG deteriorates. If the result is borderline, it should be repeated no more than 30 minutes later.