I was a top age-group triathlete and a sub-three-hour marathon runner, spent a year as an officer cadet at Sandhurst in the 1990s and had been on operational tours. Pregnancy was going to be a breeze, right? Wrong. I had never been in less control of my body and never been more aware of it. I had a strict lesson in patience, achieved through eight weeks of bed rest in my first trimester. My goal of being a super-fit triathlon mum, ready to race as soon as I'd popped out Junior, went out the window. Instead, I decided to focus on gaining back some of my aerobic fitness, working on my core and basic strength, and concentrating on my swimming technique. I spent hours on the internet and scouring books, researching various types of training during pregnancy. There is a wealth of information out there, but most of it is blogs and personal experience. Generally, the advice from doctors is that you can continue what you were doing before, but that probably doesn't apply to someone whose training schedule averaged 17 hours a week on top of a full-time job. So I needed to modify my training. After two months of bed rest, once given the all clear, I had to go back to basics. Pregnancy makes your muscles more flexible, your ligaments stretch and many of your systems (digestive, for one) slow down, all due to a hormone called relaxin. This can put you at risk of injury, especially back (sciatica) and pelvic injuries, and your core stability decreases. When pregnant, your body experiences a 40 per cent increase in blood volume, and your lungs start to get squashed Considering I have a history of pelvic instability and hamstring injuries during running, I decided that it was pointless to even try and run while pregnant. I could regain aerobic fitness doing other things. My focus was on maintaining core strength and stability, and trying to prevent postural problems and back pain in later pregnancy, while giving me a robust platform to build on post-pregnancy. At 14 weeks, I did a 20-minute treadmill walk, a 500-metre swim and two core/strength routines. The first thing I noticed was that I felt less lethargic and had more energy after each session. I took that to be a good sign. After two weeks of activity every other day, I could swim 1,500 metres, do a 40-minute elliptical trainer with a low heart rate (130 beats per minute), and my strength during weight sessions was improving. I was surprised at how quickly my basic fitness came back. I also started swim training again with my triathlon group, 26 Coaching, but I stuck to the slow lane, wore a heart rate monitor and focused on my technique. When pregnant, your body experiences a 40 per cent increase in blood volume, and your lungs (and everything else) start to get squashed to make room for the baby. It becomes important to monitor your heart rate to avoid becoming anaerobic, which decreases your ability to take up enough oxygen and could potentially reduce the amount of oxygen the baby gets. With the extra blood volume and smaller lung capacity, it's very easy to hit a high heart rate quickly. I also decided to use a personal trainer to help with my core and basic strength (back and legs), and more challenging exercises while in a safe environment. My trainer focused on core in the transverse (rotational) plane: plank work, upper and lower back strength, and a lot of one-legged stability exercises and supported squats. Lying on your back once you are into the second trimester becomes more difficult because of the weight of the baby on your aorta, but can be modified in an incline position. Lying on your front is completely out of the question and just too uncomfortable. By week 18, I had developed a routine: 75 to 90-minute swim sessions three times a week (covering about 2.5 kilometres each time), two personal trainer sessions, a spin class/turbo for 60 minutes, a 45-minute elliptical session and a two-hour hike on Sundays. It was about 10 hours in total, but all at very low intensity. If I was feeling too tired, I would rest. By 20 weeks, I had settled into my routine and particularly loved swimming. I was finding it a challenge, due to my decreased lung capacity, but was enjoying the weightlessness of the water, and the ease at which I moved in it through increased buoyancy and redistribution of weight. I stopped hiking at about 21 weeks as the hills became a challenge and I stopped enjoying it. From 24 weeks, I started to experience growth spurts and expansion, which made aerobic exercise and weight-bearing exercises much harder. In swimming, this meant concentrating even harder on my technique to pull through the water more efficiently. Core work was modified, and elliptical trainer and spinning were reduced in intensity. Throughout my second trimester, I felt strong and comfortable and made sure that I never did anything to the point of overheating or exhaustion. I continued to train in my third trimester, until I gave birth on Christmas Day. My baby girl was born early due to unrelated complications, but is healthy and is so far making good progress. I feel that much of this is due to my fitness during the pregnancy, which meant she was better able to endure the stress of the natural birth (she was breech) and the neonatal environment. My own recovery was very quick as well - I was hiking within a week and doing Pilates after 10 days. Pregnancy is also known to be a performance enhancer: in 1983, Norway's Ingrid Kristiansen won the Houston Marathon five months after having her first child. I have set my sights on the Ironman Western Australia in December. Ambitious, maybe, but we all need a goal.