Heart disease is the leading cause of maternal death in the UK – but in 77% of cases the women were unaware of a heart condition before they became pregnant, according to a study.
Doctors often ignore the warning signs, mistakenly believing heart problems would not strike young women, it said.
Yet pregnant women are at extra risk because of the strain carrying a baby places on the heart and for those with underlying conditions pregnancy can be fatal.
The symptoms of cardiovascular disease can be masked by the pregnancy.
Experts said all women should ask relatives about their medical history before having a child, to check whether there is a family history of heart problems.
Maternal death rates linked to heart problems have doubled since the 1980s, the report reveals.
The Confidential Enquiry into Maternal Deaths found that one in four maternal deaths are linked to cardiac disease.
One of the authors, Dr Rachael James, consultant cardiologist at Sussex Cardiac Centre, who will present the findings at the British Cardiovascular Society conference in Manchester, issued a warning: "This inquiry highlights, once again, that we need to see action being taken to stop young women dying from heart disease."
She added: "Women trying for a baby or mothers-to-be should also look at their family history for the possibility of any undiagnosed inherited heart conditions, which are often marked by the sudden or unexplained death of relatives." – Daily Mail