During pregnancy, a woman's heart rate is estimated to increase by at least 25 per cent. This can place women at a higher risk of a range of heart conditions – some of which are easy to manage once diagnosed and some much more dangerous.

"Pregnancy is an exciting time, but it is a time of heightened risk for the manifestation of heart disease," explains Dr Monique Watts. "Heart disease is a growing complication of pregnancy, so it is important that patients and doctors alike are aware of the potential for heart problems."

"Pregnancy acts like a stress test for the heart. Conditions that were present but perhaps not causing any symptoms prior to pregnancy can become problematic due to the huge cardiovascular changes that occur with pregnancy," Dr Watts tells Bounty.

"Due to the increase in volume of blood being pumped by the heart and the relaxation of the blood vessels and other hormonal influences, the awareness of extra heart beats or abnormal heart rhythms increases.

"This can manifest as one of the more common symptoms in pregnancy called "palpitations", which is the feeling of the heart beating harder or faster than usual. While the sensation of palpitations can be a normal part of pregnancy, it can also be an indicator of an abnormal rhythm, which can cause problems and requires treatment."

Dr Monique Watts is a cardiologist and a Her Heart Medical Ambassador.

34-year-old Kate El-Halabi was 20 weeks into her second pregnancy when she fainted for the first time.

Her first pregnancy had been all smooth sailing, and Kate had always been fit and well. In fact she was ranked #48 in Australia for tennis. So when her arms felt too weak to even hang out the washing she knew something was not quite right.

"I was in the food court following my glucose test, when I fainted," says Kate. "I woke up with everyone around me, and was taken for tests but nothing showed up.

"In all I fainted about five times during my pregnancy and I would always go straight to hospital but nothing was ever caught."

Kate El-Halabi was diagnosed with Supra Ventricular Tachycardia (SVT) 20 weeks into her second pregnancy.

Eventually at 36 weeks, and ECG found Kate's heart was beating at a dangerous 290 beats per minute. Kate was diagnosed with Supra Ventricular Tachycardia (SVT) or an abnormally rapid heart rhythm where the electrical impulse in the heart is firing off too many at one time.

Kate's heart rate wouldn't come down so she ended up having an emergency caesarean and now, post-baby Kate remains on two types of medication to keep her SVT in check.

"There are some conditions that can occur which are unpredictable, but being healthy prior to pregnancy is a great way of doing the most to ensure you stay well during pregnancy," says Dr Watts.

"Being a healthy weight, eating well, exercising regularly and have a healthy blood pressure prior to pregnancy are all great ways to reduce your risk during pregnancy. It's also important to realise that being a young woman doesn't mean you can't have heart disease. Cardiac problems are on the rise in pregnant women, so it's critically important that women speak up about their symptoms."

WATCH: Kate's story. Continues after video …

In 2017, Belinda Mullans suffered a heart attack brought on by Spontaneous Coronary Artery Dissection (SCAD). Belinda had just turned 30 and had given birth to her second child, Lucy, nine weeks prior.

"My pregnancy was all normal, and it was closely monitored, because my first child, Jack had been born severe cerebal palsy after a brain haemorrhage," explains Belinda.

"And I was always well, if a little anxious about the delivery because of my previous experience."

Like Kate, Belinda was a fit and healthy woman. An active state level volleyballer, with low cholesterol, Belinda wasn't overweight, didn't drink or smoke and had no family history of heart disease.

So when she woke up one morning with debilitating chest pain, a heart attack was the furthest thing from her mind.

"I had so many balls in the air with my son who had special needs and a newborn baby, I just sort of tried to carry on," explains Belinda.

Belinda Mullans suffered a heart attack brought on by Spontaneous Coronary Artery Dissection (SCAD) nine weeks after the birth of her second child.

Belinda visited her GP and had bloods ordered, but it was not until the next day that it was confirmed that Belinda had suffered a heart attack brought on by Spontaneous Coronary Artery Dissection (SCAD).

SCAD occurs when there is a tear in one of the blood vessels in the heart. The tear blocks the blood flow to the heart and causes a heart attack. 90 percent of SCAD cases are women, mostly aged between 30-50, generally healthy like Belinda with no prior risk factors for heart disease.

The following week, during an angiogram investigating what had happened, the cardiologist caused a tear with the catheter causing another SCAD and heart attack.

That was not the last of it though, Belinda's third SCAD and heart attack occurred in 2010 after a stressful period of her life, and this time was treated with blood thinners which she continues to take together with an ACE Inhibitor.

"Rehabilitation was funny," laughs Belinda. "I was in there with lots of 80 year olds, there's not many young mums in there walking around a room trying to improve their heart health."

And while she is now able to participate in sports again, it toolk Belinda a long time to get her confidence back. Particularly when it came to being around the children on her own.

"I'm a mum with a special needs child, so I need to be very careful stress. I have had to learn ways to manage that more effectively."

What symptoms should we looking for and when should we seek help?

"It can be difficult for pregnant women to know which symptoms to attribute to pregnancy and which could be indicative of a heart problem," says Dr Watts.

"Symptoms like chest pain, arm pain or jaw pain should be considered an emergency and assessed urgently. Even losing consciousness, while possibly a simple faint, can also be a sign of a more serious problem so warrants prompt assessment.

"Other symptoms that should never be ignored and should be discussed with your doctor are things like the feeling of a racing heart, extreme fatigue, significant breathlessness or new ankle swelling."

Her Heart is a not-for-profit dedicated to raising awareness around women's heart disease. It is the go-to-place for Australian women to access the latest research findings, clinical information, health and lifestyle advice around heart disease for women. Her Heart's mission is to reduce heart disease in Australia for women by 50 percent by 2025.