Maternal bereavement - the death of a parent, sibling, or previously born child - within six months before conception may be linked to an elevated infant death rate, a new study has found.
"Our findings suggest that the six-month period prior to pregnancy may be a sensitive developmental period with implications for early offspring mortality," researchers said.
However, maternal bereavement during pregnancy does not affect the infant mortality rate, they said.
Using a Danish nationwide birth registry, the researchers led by Quetzal A Class, who was at Indiana University during the study and is now a postdoctoral researcher at the University of Chicago, analysed data from all women who gave birth in Denmark between 1979 and 2009.
Infant and child mortality rates were compared for women with and without maternal bereavement in the months before conception or during pregnancy.
The analysis included data on nearly 1.9 million singleton births. Overall mortality rates were 0.004 per cent during the first month of life, 0.002 per cent between one month and one year, and 0.001 per cent between one and five years.
The results showed increased mortality for infants born to mothers who experienced the death of a family member in the months before conception.
After adjustment for other factors, risk of infant death during the newborn period (before one month) was more than 80 per cent higher for women with preconception bereavement.
For infant death between one month and one year, risk was about 50 per cent higher for women with bereavement before conception.
The associations were weakened - but still significant - after further adjustment for gestational age and birth weight.
The increases in infant mortality were significant only between zero and six months before conception. Preconception bereavement had no effect on the risk of child death between age one and five years.
Bereavement during pregnancy was unrelated to infant or child mortality.
The researchers concluded that maternal bereavement within six months before conception is linked to an increased infant mortality rate.
While the absolute risks are very low - a small fraction of a percentage point - the relative increases in infant mortality risk may be substantial.
Grieving may lead to changes in the maternal stress system affecting offspring development - particularly during the vulnerable period of early organ development - or alter the mother's biological preparedness for pregnancy.
The study was published in the journal Psychosomatic Medicine: Journal of Biobehavioural Medicine.
