The study is not the first to suggest that a mother's psychological state can influence her unborn child's brain development, but it is the largest, involving nearly 1.4 million Danish children followed for decades.
The schizophrenia risk was still quite small in the children of women who experienced the death of a family member early in pregnancy, and the findings need to be confirmed.
But researchers say the study adds to the evidence that severe stress early in pregnancy -- in this case the death of a parent, sibling, spouse, or child -- may negatively impact fetal brain development.
"We did not see this association in the months before pregnancy, or after the first trimester," says study co-author Kathryn M. Abel, PhD, of the University of Manchester.
Stress and Schizophrenia
Abel and colleagues from the University's Center for Women's Mental Health Research examined data from a comprehensive, nationwide Danish health registry, which recorded about 1.38 million births in the country between 1973 and 1995.
The same registry was used to determine if mothers who gave birth during this time had first-degree relatives who died, received a diagnosis of cancer, or had a heart attack or stroke during their pregnancies.
Roughly 22,000 women experienced the death of a close relative during pregnancy, and about 14,000 had a relative treated for a life-threatening illness.
A total of 7,331 schizophrenia cases were identified among Danes born between 1973 and 1995 over at least two decades of follow-up.
Being born to a mother who had a close relative die during her first trimester was found to be associated with a 67% increased risk for schizophrenia.
But a similar death up to six months before conception or at any other time during pregnancy did not appear to elevate risk, nor did having a seriously ill relative during pregnancy.
Abel tells WebMD that the research team plans to repeat the study using the Swedish health registry, which is more than twice the size of the Danish one.
The newly published study appears in the February issue of the journal Archives of General Psychiatry.
"We also want to expand the research to look for other mental health outcomes," Abel says. "I think it is highly likely that if we look at a broader spectrum of psychiatric disorders we will find that those are increased as well."