NEW YORK - Parents who've suffered the death of an infant may have a higher-than-normal risk of stillbirth in the next pregnancy, a new study suggests.
Stillbirth refers to the death of a fetus after the 20th week of pregnancy. It's known that, as a group, women with a history of stillbirth have a higher-than-average risk of suffering another.
But the new study suggests that the death of a baby in the first year of life also points to an increased risk of stillbirth in the next pregnancy.
Researchers found that among more than 320,000 women, the rate of stillbirth during a second pregnancy was just over four per 1,000 births. But the risk was nearly three-fold higher for women who'd lost their first baby before the child's first birthday, versus mothers whose first baby survived.
It's not entirely clear why the relationship exists. But the researchers say the findings suggest that women who've lost a baby should be counseled before their next pregnancy.
"What we're trying to do is, look at women's history and see if we can identify mothers who are likely to be at higher risk of stillbirth," said Dr. Hamisu Salihu, a professor at the University of South Florida in Tampa who worked on the study.
The precise cause of a woman's stillbirth is often unknown. In fact, that's true in about 50 per cent to 60 per cent of cases, Salihu told Reuters Health.
But there are certain risk factors linked to stillbirth that are changeable. Obesity and smoking are two, Salihu noted.
In addition, certain health conditions in the mother -- like high blood pressure or diabetes that arise before or during pregnancy -- are tied to stillbirth (because they can lead to problems with the placenta or affect the growth of the fetus).
So Salihu suggested that couples who've lost a baby visit with their doctor before their next pregnancy to talk about any modifiable risk factors for pregnancy complications. During pregnancy, a woman may need to make more-frequent prenatal care visits to monitor for problems, depending on her situation.
"That has to be decided on a case-by-case basis," Salihu said.
The findings, published in the obstetrics journal BJOG, are based on medical records from 320,350 Missouri women who had their first and second pregnancies between 1989 and 2005.
Of those women, 2,483 -- about eight per cent -- lost their first baby before the child's first birthday. And they had a three-fold greater risk of having a stillbirth with their next pregnancy compared with women whose first baby survived.
Black women had a particularly elevated risk: Those who'd suffered an infant death were more than four times more likely to have a stillbirth than black women whose first baby survived.
That finding is in line with past research showing that African-American women face a higher stillbirth risk than white women do.
It's not clear from the study why infant deaths were linked to stillbirth risk in the next pregnancy. But Salihu said it's possible that the same underlying factors that contributed to the first baby's death -- whether genetic or environmental, like poor growth due to smoking -- also contributed to fetal death in the second pregnancy.
In support of that idea, the researchers found that the death of a newborn -- versus an older baby -- was more strongly linked to stillbirth risk in the next pregnancy.
The overall stillbirth rate in the study was 0.4 per cent. So even with a relatively increased risk, most couples who've lost a baby would not have a stillbirth next time.
"Couples should not give up," Salihu said. What they should do, he added, is get "preconception" counseling to try to spot any known risk factors for stillbirth.
"Some of those risk factors are modifiable," Salihu said.