According to research appearing in the September, 2000 issue of The Lancet, women who are under stress during the first trimester of their pregnancy are more likely to give birth to a child with birth defects than women who are not under stress. The researchers reviewed the medical records of women and looked for sources of extreme stress—like severe illness of a partner or child or death of a loved one. The stress occurred during the pregnancy or up to 16 months before the pregnancy. The researchers identified 3,560 women who had such stress and compared them to over 20,000 pregnancies where the women did not have extreme stress.
There were 42 women in the stress group who gave birth to a child with birth defects; this constitutes 1.18% of those pregnancies resulting in a birth defect. In the control group, only 0.65% of the pregnancies resulted in a birth defect. This represents an 80% increase in risk. If the death of an older child occurred during the pregnancy, it created a five-fold increase. If that death was unexpected, it created an eight-fold increase in the likelihood of producing a birth defect.