This satnav of the labour ward is driving us the wrong way Birth monitors cost the NHS millions, and were never meant to replace a labouring woman's default help: the midwife

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When I gave birth to my first child ... I was as prepared as I could be: positions, breathing, birth plan. What I hadn't accounted for was an uninvited, domineering presence in a corner of the room that would so dictate proceedings that no one dared act without referring to it. The cardiotocography (CTG) machine, the silent birth partner.

CTG machines measure fetal heart rate and uterine contractions and are now omnipresent in labour wards, but it was never meant to be this way. When they were first developed ... they were to save lives by detecting the early stages of hypoxia – babies starving of oxygen in the womb. Following their introduction ... from the early 1970s, perinatal deaths went down (although this also coincided with better antenatal screening), but for the last 10 years this figure has remained static. And the number of babies born with cerebral palsy has not decreased in the last 100 years (it's still not known if cerebral palsy is absolutely a birth injury, or happens at another time).

Meanwhile, there is increasing litigation against the NHS directly related to the misinterpretation of cardiotocograms (CTGs) resulting in babies born dead or damaged. The cost of these lawsuits has risen sevenfold in four years: from £11.8m in 2006 to £85.8m last year.

Without question that CTGs save lives, but there is a big problem – like all equipment they are only as good as the people operating them, and results can be difficult to interpret ... they can lead to false positives, which can lead to unnecessary intervention. And because CTGs are a monitoring, not a diagnostic tool, the results should never be read in isolation but as part of a jigsaw.

My first labour ... resulted in various interventions – induction, forceps, emergency C-section, lumbar puncture for my baby, IV antibiotics ... - many triggered by the CTGs on which we all, slavishly, started to rely. Looking back, I can only compare parts of it to otherwise rational, intelligent people over-relying on satnav and driving up one-way streets, simply because a machine told them to. There were times when the midwives attending paid more attention to the machine's spewing paper tongue than me. Look at me, I wanted to say, look up.

With CTGs, one midwife can sit in front of a central monitor and keep track of several women in one go. "CTGs are the only way," one senior member of maternity staff told me, "to stretch one midwife over more than one woman." Contrary to popular belief, things don't go wrong in labour from one minute to another, there are warning signs – signs a CTG can pick up, but there has to be someone there to interpret the data and get appropriate help quickly. Otherwise CTGs ... [provide] a false sense of security.

With hindsight and after much analysis ... there was no real evidence to show my daughter was indeed ever in distress, so I'll never know if the C-section saved her life or if I took up unnecessary medical time and resources. But at least I had the luxury of musing with a live, healthy baby. About 500 babies die each year as a result of misinterpretation of CTGs.

After the birth I became highly involved with maternity services ... The most harrowing case I ever sat in on was that of a woman whose baby showed obvious signs of distress, but the medical staff attending only looked at the last few sheets of the printout ... In other words, instead of flinging their arms wide and looking at data that would have given them a good overview, their hands did no more flicking than if they'd been reading a paperback book.

There is another major problem, which has nothing to do with CTGs per se ... Remember those unnecessary interventions mentioned earlier? With increasing C-sections ... doctors are performing C-sections that may or may not be necessary and have often been decided on by the (mis)reading of a CTG, and there are other women whose babies desperately need C-sections, but are not getting them at all, or in time. Some babies are being monitored to death.

This is not a problem that is going to go away. We have a shortage of midwives that is entirely cash-led ... The more continuous the care a woman receives, the less chance of a breakdown in communication. There will now be much talk of retraining staff in the reading of CTGs ... and certainly that's important. But, yet again, it's a misreading of the situation. The CTG machine was never meant to be the labouring women's default companion: an experienced midwife was.

The standard of care requires that if a woman is continuously monitored, she should have one-to-one midwifery care. Instead what we often see is one midwife caring for 2 - 3 women at a time and a central monitor at the staff station so that any midwife or doctor in the staff station can monitor all of the active monitors that are in use.