Cardiotocography provides a simultaneous record of the foetal heart rate and magnitude of uterine contractions.
The foetal heart rate is recorded in the first instance using a abdominal doppler ultrasound sensor. If this proves inefficient then a foetal scalp electrode may be attached during labour.
Maternal contractions are recorded using an abdominal wall pressure sensor. The recorded strength of a contraction is only an estimate as it is altered with position, abdominal wall obesity. However the length of a contraction does provide useful information in the interpretation of foetal heart rate abnormalities.
The fetal heart increases with increasing gestational age. There is an increase in heart rate variability with increasing maternal age.
NICE suggest that (1):
- evidence does not support the routine use of antenatal electronic fetal heart rate monitoring (cardiotocography) for fetal assessment in women with an uncomplicated pregnancy and therefore it should not be offered
- NICE (2003). Antenatal care
- BMJ 1993; 306: 347
- Grant, A.M. Oxford database of perinatal trials 1992; Version 1.3, disc issue 8: record 3298 OUP.
- Nelson, KB. et al. Uncertain value of electronic fetal monitoring in predicting cerebral palsy. NEJM 1996;334(10): 613-618.
Last reviewed 01/2018