Caesarean scar pregnancies, in which an embryo embeds into scar tissue left by caesarean sections, can cause the uterus to rupture and hemorrhage with little warning or pain, leading to death unless the woman is treated immediately. It is rare but the incidence has been increasing around the world in line with the caesarean rate, which now stands at 31% in Australia.
A study in the International Journal of Obstetrics and Gynaecology last year found that most caesarean scar pregnancies were terminated in the first trimester because the growing embryo could rupture the uterus or the placenta could grow through the lining of the uterus and adhere to the bladder.
In October the King Edward Memorial Hospital in Perth reported it had handled nine cases in five years, with five women having to undergo chemotherapy and one having an emergency hysterectomy.
The president of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists, Christine Tippett, said ultrasound allowed early diagnosis.
"Caesarean section scar pregnancies, which can only be detected through transvaginal ultrasounds, have very significant implications for women," Dr Tippett said. "The problem is that they are not associated with the same pain you get in a tubal ectopic pregnancy, so often a woman doesn't know about it until it ruptures."
A fitness instructor and former television panellist, Sharon Evans, 39, a mother of two, had two caesarean scar pregnancies within 10 months, resulting in seven weeks of chemotherapy and four operations. "I can't believe some women would opt for a caesarean," she said.
"I had to have one when my second daughter was a breech baby, but I had no idea it would lead to this. I've been through hell in the past year and … I tell anyone not to have a caesarean unless it is a medical requirement."
Ms Evans, from North Balgowlah, NSW, said: "The second time I got pregnant, I was just gobsmacked. It had happened again and this time it was twins." She has decided not to have more children.
"Why would anyone have a caesarean if you can have it naturally? I just want people to stop and think about it. It is not minor surgery. It is very, very painful and very invasive and horrific complications can come from it."