Assessing fetal wellbeing in pregnancy and labour
The aim of assessing fetal wellbeing in pregnancy and labour is to achieve the birth of a healthy baby. This is can be done by confirming normal fetal growth and development, but also early detection of deviations from the norm so timely intervention can take place.
Assessment can be accomplished in a number of ways, including antenatal screening and diagnostic testing (Box 33.1), measuring fetal growth, ultrasound scanning and monitoring fetal movements. Assessing maternal wellbeing also provides vital clues, as poor maternal health may negatively impact on the fetus.
All pregnant women are offered an ultrasound scan (USS) at 10 to 13 weeks to:
- Assess fetal viability
- Date the pregnancy
- Undertake nuchal translucency screening for chromosomal abnormalities.
A further scan is offered at 18–20+6 weeks to detect fetal structural abnormalities. Third trimester scans are not routinely offered although there is some research suggesting they have a place in detection of intrauterine growth restriction (IUGR).
Further USS will be offered if indicated:
- To accurately assess the position of the fetus
- For suspected IUGR
- Women at high risk of IUGR.
If symphysis fundal height (SFH) measurement is likely to be inaccurate, such as with high BMI (e.g. a BMI over 35) or multiple pregnancies, women may be referred for serial assessment of fetal size. Women who have risk factors for IUGR should be offered routine umbilical artery Doppler scans from 26 to 28 weeks of pregnancy.
Women should be encouraged to monitor fetal movements (FM) and should report if their number reduces or the pattern changes. Whilst perception of FM will vary, most women can identify when the frequency reduces significantly.
For reduced fetal movements (RFM) under 28 weeks’ gestation the fetal heart (FH) should be auscultated with a hand-held Doppler. If the FH is heard, reassure the woman. There is no evidence supporting the use of cardiotocograph monitoring (CTG) or USS in the absence of other clinical indications.
After 28 weeks’ gestation women should be advised to lie on their left side and focus on FM for 2 hours. If they do not feel 10 or more movements in 2 hours, they should contact maternity services.
Women with significantly reduced or absence of FM should contact maternity services immediately and be monitored using a CTG to exclude fetal compromise. Women with recurrent RFM should be reviewed and undergo further investigations such as USS to assess growth and liquor volume.
Abdominal examination and palpation is fundamental to assessing fetal wellbeing. See Chapter 25.
Assessing fetal growth is a key means of assessing fetal well-being. From 24 weeks’ gestation the SFH should be measured at every appointment and plotted on a growth chart (Figure 33.1, which can be found in the Appendices at the end of the book). The RCOG recommends the use of customised growth charts. If the SFH measures below the 10th centile on one occasion, or slow or static growth is demonstrated on serial measurements, the woman should be referred for USS assessment.
- Ensure privacy.
- Position the woman in a supine position with her legs extended.
- Wash hands.
- Palpate the abdomen to locate the fundus (Figure 33.2).
- Use a single patient use tape measure with the centimetres on the underside to reduce the risk of bias
- Secure the tape at the fundus with one hand. Keeping the tape in contact with the skin, measure along the longitudinal axis of the fetus to the upper border of the symphysis pubis without correcting to the abdominal midline (Figure 33.3).
- Measure only once.
- Wash hands.
- Document the distance in centimetres on a customised growth chart.
During abdominal palpation abnormalities of liquor volume may be suspected. Polyhydramnios, too much liquor, may be suspected if the uterus appears larger than expected, looks tight and shiny and feels tense to palpate. A fluid ‘thrill’ may be seen if the abdomen is tapped.
Oligohydramnios, too little liquor, may be suspected when the uterus feels small and compact. The fetal parts may be easily palpated. Both polyhydramnios and oligohydramnios can be confirmed by USS.
A pinard or fetal stethoscope should be used for the initial assessment to confirm that the sounds are the FH as the maternal pulse may be picked up by electronic methods and mistaken for the FH. The maternal pulse should be palpated simultaneously to establish a difference in rates to further confirm it is the FH being auscultated (Figure 33.4).
A key indicator of fetal wellbeing is maternal wellbeing. If the mother is unwell this is likely to impact on the fetus. The midwife should assess maternal wellbeing, including observations of vital signs and urinalysis.
Women should be asked about FM at the first point of contact during labour. Women reporting reduced FM should be monitored using electronic fetal monitoring (EFM) throughout labour. FM during labour is an indication of a healthy fetus. FM should be anticipated following stimulation such as a vaginal examination, and the absence of such may indicate fetal compromise.
The FH should normally be auscultated every 15 minutes in the first stage of labour and every 5 minutes or after every contraction in the second stage for women. Auscultation should take place after a contraction for 1 minute and the rate should be counted and recorded.
Liquor is usually clear and has an inoffensive smell. A change in colour from clear to green/brown may indicate the liquor is contaminated with meconium. This may be a sign of fetal distress. Whilst a pinkish tinge may be normal, any significant blood staining may be a sign of haemorrhage. An offensive smell is indicative of infection.