Pregnant women are being told to look out for the symptoms of heart disease, which is now the leading cause of death in the months before and weeks after childbirth.

Two in every 100,000 women who gave birth between 2009 and 2014 died as a result of heart disease in the UK – nearly a quarter of all maternal deaths in the period, according to an audit led by the medical royal colleges.

Some women are unaware they are at risk because they do not know they have heart disease, and pregnancy and childbirth put a strain on the entire body.

The UK figures came from an investigation by medical experts into the care of 153 women who died in the UK and Ireland as a result of heart disease between 2009 and 2014. Carried out for the latest Confidential Enquiry into Maternal Deaths report, the research found that some had a severe chest pain spreading to the left arm or back, typical of a heart attack, but did not tell their doctor or midwife.

Prof Marian Knight, who is from the Nuffield department of population health in Oxford and led the research, said: “While dying from heart disease in pregnancy or after childbirth is uncommon, women need to be aware that they may be at risk, particularly older women. It is important to seek advice from your doctor or midwife if you have severe chest pain which spreads to your left arm or back. Being breathless when lying flat is not normal in pregnancy, and may also be an indication of heart problems.”

In some cases, staff knew a woman had a heart problem but did not realise her pregnancy and labour could be at risk.

Women were still dying in pregnancy, childhood and the first year of motherhood at the same rate as several years ago, according to the audit, meaning it would be difficult for the government to hit its target of halving maternal deaths by 2030.

Particularly troubling was the mental health of women who had given birth: the report showed that the suicide rate in the first year had not dropped since 2003.

Between 2009 and 2014, 111 women killed themselves in the UK during or up to a year after the end of pregnancy – 20 of them during or within 42 days of the end of pregnancy. It is the leading cause of direct maternal deaths occurring up to one year after the end of pregnancy.

Between 2012 and 2014, 241 women died during or within 42 days of the end of pregnancy in the UK. The deaths of 41 women were classified as coincidental, bringing the maternal death rate to 8.54 per 100,000 pregnancies.

But there had been some successes. In the 60 years since the regular audits began, deaths from problems related to high blood pressure had dropped to their lowest rate ever, at fewer than one for every million women giving birth, down from 150.

“This is a testament to the translation of research into practice and the high quality care provided to these women as a consequence,” the report said. “On a worldwide basis, however, hypertensive disorders remain one of the most frequent causes of maternal death – over the same period that one woman dies in the UK, 20,000 die worldwide.”

Deaths from sepsis, or blood poisoning, were low in the most recent period because fewer women caught flu, partly because they were urged to get a jab in pregnancy and partly because there had not been major flu outbreaks in recent years, the report said.

The maternal death rate in the UK remained low, said Prof Lesley Regan, the president of the Royal College of Obstetrics and Gynaecology.

“Maternity care in the UK is both safe and effective. However, one death is too many and as healthcare professionals we must learn from these unfortunate deaths in order to prevent them in future,” she said. “We need to place women at the centre of their care, educating them and empowering them to seek healthier lifestyles.”

Health services could fix only one third of the problem, with lifestyle changes and a reduction in health inequalities needed for the remainder, Regan told the Guardian in an interview.

The Birth Trauma Association called for more resources to be invested in women’s mental health around pregnancy and after childbirth. “It’s not just about improving mental healthcare after birth, though that is important. We know from our members that their mental health problems derive, in many cases, from poor care during labour and birth,” said Kim Thomas of the BTA.

“A greater concern for safety, a woman-centred approach to care and improved team working between midwives and obstetricians could all help to prevent mental health problems developing after birth.”