A study involving 125 women has found the first, direct human evidence that fetuses exposed to elevated levels of the stress hormone cortisol may have trouble paying attention or solving problems at 17 months. But more hopefully, the association only occurred among children showing insecure attachment to their mothers, independent of socioeconomic factors. The findings suggest that a stressful prenatal environment may be effectively counteracted by good parental care. The children will be followed up when they turn 6.
Good parenting counteracts prenatal stress
 Maternal Prenatal Cortisol and Infant Cognitive Development: Moderation by Infant-Mother Attachment. Biological Psychiatry. In Press, Corrected Proof,(2010).