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Monitoring childbirth and labour is moving beyond the limits of CTG

20 November 2019
Cardiotocography has been a flawed technology in childbirth

When an almost universal piece of medical equipment nearly brought tragedy to the birth of her second child, Sarah McDonald decided to build something better. She just needed a PhD in medicine to do it.

A contemplative Sarah McDonald, with hands cupped in front of her, in a brightly lit room with dramatic shadows behind.

Labour of love. Sarah McDonald devoted herself to creating a transformative technology. Now her focus has widened to getting it produced and used.

Not every woman can stop in the throes of labour and think, ‘There’s got to be a better way.’ And certainly, not every woman would think, ‘I will find a better way.’

But that’s exactly what Sarah McDonald did.

McDonald was 32 weeks pregnant with her second child when she was rushed to hospital with premature contractions. For the next week, those contractions continued. Anyone who’s endured a day of labour pains will know that sticking it out for an entire week is close to torture.

Making things worse was the cardiotocography monitor (known as a CTG) that she had to wear continually, like countless expectant mothers before her. Its two thick fabric bands were stretched across her stomach and she was told not to move because it would affect the readings.

Again, anyone who’s ever been in labour will know the relief that comes with changing position, taking a short walk and having a shower. With the monitor on, McDonald couldn’t do any of these things.

The discomfort was one thing. But when McDonald, who studied mechatronic engineering and describes herself as “problem solver”, began questioning what the bands were actually doing, her frustration grew.

“Foetal heart rate and contraction frequency are open to highly subjective interpretation,” she says. “In my case, the doctors were not getting a quantifiable indication of my condition or the baby’s. The monitoring was a box-ticking exercise.”

It is a mandated part of procedures that medical staff use the CTG or something similar in specific circumstances, whether or not the data is useful – or even reliable. Certainly, CTG is associated with a higher rate of caesarean sections and instrument births, with their attendant risks.

A tangle of blue and pink straps and wires. The outmoded cardiotocography monitor (known as a CTG), on a black background.

All too familiar to many women in labour, the standard cardiotocography monitor limits movement and can easily deliver inaccurate information.

While Oliver is a thriving little boy now, he was born with just a 20 per cent chance of survival. The inability of the CTG data to usefully quantify what was happening, led to the decision to conduct a caesarean section delivery at just 33 weeks. This meant Oliver’s lungs were not fully developed when he was born. “It was an horrific experience,” says McDonald.

If the clinicians had more accurate information to help them determine was happening, McDonald attests, Oliver might have been born later and had a greater chance to develop vital organs. "People in the community might think everything is known about childbirth and what we do now is best practice,” says McDonald. “But my experience, and that of many other mothers, shows that we have a long way to go.”

Speaking energetically and packing in a lot of information, McDonald pauses for breath. “So, the way forward was to make sure no mother ever again goes through what I went through.”

For McDonald, that meant inventing the Oli™, (named, of course, for her son), as an entirely new monitoring system for women in labour. To do this she added a PhD in medicine to her existing engineering and commerce degrees, doing the PhD under her former engineering supervisor and clinicians from Royal Prince Alfred Hospital. It was a mighty leap from stay-at-home parent to PhD student, and it happened during baby Oliver’s first year. McDonald hasn’t looked back. 

McDonald's minimalist Oli™ device with four, short blue arms and a square, white centre, on a pale background.

Smaller, more reliable and able to collect a wider range of information, Sarah McDonald's invention could transform the childbirth experience.

The cross-disciplinary approach was essential because the device couldn’t be, in McDonald’s words, ‘this crazy engineer’s idea’. She had to be able to convince the medical establishment that this device was more than needed, it would work with them and for them to reduce unnecessary interventions, identify complications early, and improve outcomes.

In other words, the Oli™ will reduce the kind of guesswork that led to Oliver’s pre-term delivery.

Developing the device, McDonald spent time on the obstetrics ward, learning from midwives and obstetrician-gynecologists what was needed for women in both pregnancy and labour. That cross-collaboration proved key, she said, in designing a device that would deliver the best results for all users.

It’s been half a century since any true advance in obstetric monitoring; even the CTG was only designed to automate what doctors used to do manually – check foetal heart rate and number of contractions. It’s in no way capable of measuring what we now know is an array signs needed to accurately understand what is happening during pregnancy and childbirth in order to make truly informed decisions.

“For example, knowing foetal heart rate isn’t nearly enough information to have, and cannot be read in isolation,” says McDonald. “Birth is an intense experience for the baby as well, so even in a perfect birth, at particular stages the baby’s heart rate will be all over the place.”

“Birth is an intense experience for the baby as well, so even in a perfect birth, at particular stages the baby’s heart rate will be all over the place.”
Sarah McDonald

The Oli™, couldn’t be more different from the cumbersome and unreliable CTG. A small, lightweight device, it sticks to the belly, monitoring not just contractions and foetal heart rate, but uterine activity, maternal and foetal wellbeing, level of exertion of the mother, and movement. It does all this wirelessly, allowing the mother to move around freely.

Though the Oli™ isn’t on the market yet, McDonald thinks that might happen after the clinical trials,  currently scheduled for around the end of 2021. It promises to be a game-changer for obstetrics.

Building a medical device is one thing but selling that product to potential investors is another new skill set for engineer McDonald. Though she’s raised close to $5 million in funding, from Government grants, prizes and her own investment, she admits that it hasn’t been easy. “I’ve had to learn to trust my gut. You can’t compromise your vision because an investor wants to change your product.”

Not surprisingly, investors want to get the product to the market quickly, to the largest possible number of buyers and with minimal risk, “All this is difficult when you’re dealing with medical devices,” says McDonald. Certainly, she sees the Oli™ as something to be used by doctors and hospitals, rather than making it publicly available. This is important so expectant mothers aren’t falsely reassured or made unnecessarily anxious.

“It puts extra pressure on those mothers, not to mention on the health system. It’s basically the opposite of what we’re trying to do,” says McDonald.

The whole Oli™ process has brought some realities home to McDonald about what it can take sometimes for necessary advances to be made.

“No-one has been looking at this problem in this way,” she says. “The only reason I’m looking at it is because I happened to be a mechatronic engineer who had a normal birth followed by a very difficult birth which allowed me to see the differences between the two and ask practical questions about it.” 

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