Women who have problems of the placenta during pregnancy are at increased risk of early heart disease, a study shows.
Women should try to maintain a healthy weight before, during and after pregnancy
Affected mums should be closely monitored for six months after giving birth and adopt healthy heart lifestyle measures, the authors told The Lancet.
The placental problems include pre-eclampsia (pregnancy-induced high blood pressure) and other conditions where placental blood flow is impaired.
The Canadian authors believe maternal obesity might be behind the problem.
In the last decade in the UK, the number of pregnant women seen by midwives who are obese has more than doubled, they pointed out.
Obesity is known to increase the risk of many diseases, including cardiovascular disease and diabetes.
Dr Joel Ray and his team at the University of Toronto looked at over a million women who were free from cardiovascular disease before they had their first baby.
The researchers followed what happened to the women for an average of nine years after giving birth and recorded the presence of cardiovascular disease.
Overall, 75,000 of the women were diagnosed with "maternal placental syndrome" - namely pre-eclampsia, high-blood pressure during pregnancy, placental abruption (premature detachment of the placenta from the wall of the uterus, causing bleeding) or placental infarction (an area of dead tissue in the placenta due to blocked circulation in the area).
They found that women who had maternal placental syndrome had double the relative risk of premature cardiovascular disease.
The women experienced heart problems at an average age of 38.
The risk was further increased if the woman's baby had restricted growth or died in the womb, or if the woman had pre-existing risk factors for cardiovascular disease, such as tobacco smoking.
Dr Ray said: "We should try to ensure that women are a healthy weight before they enter reproductive years.
"In doing so, their future near risk of...maternal placental syndromes and cardiovascular disease might be reduced."
He said maternal placental syndrome should now be considered as an additional risk factor for cardiovascular disease in women.
"Affected women should have their blood pressure and weight or waist measured about six months postpartum, and healthy lifestyle should be emphasised," he advised.
Ellen Mason of the British Heart Foundation said: "Further research is needed to determine how seriously these pregnancy related conditions could affect a woman during her lifetime."
She said it was important for women to think about how their lifestyle could affect their own health and that of their baby.
"The best way for a mum to look after her own health and her baby's is to maintain a healthy lifestyle."