American researchers from New York University have found that exposure to stress during pregnancy may affect gestational age and the probability of a preterm baby (a baby born before 37 weeks of gestation).
The researchers considered data on pregnant women who were exposed to the 2005 Chilean earthquake. These women were compared to other Chilean pregnant women one year previous to the earthquake. Other data was also obtained on Chilean pregnant women who were living in areas which were unaffected by the earthquake. Comparisons were made based on the length of gestation at the time of the earthquake and the length of gestation at the time of birth.
The study found the mothers who resided the closest to the epicentre of the earthquake were at greater risk of experiencing a premature birth. This relationship between stress and premature child birth was found to be evident when the women gave birth to a female. This effect was most statistically significant when the mother experienced the stress (earthquake) during the second and the third trimester. No statistical difference was found for male births.
Reference: Torche, F., Kleinhaus, K. Prenatal stress, gestational age and secondary sex ratio: the sex-specific effects of exposure to a natural disaster in early pregnancy. Human Reproduction: 2011.