There is good evidence, from independent prospective studies, that if the mother is anxious /stressed while pregnant, her child is substantially more likely to have behavioural, emotional or cognitive problems. An increased risk of attention deficit/hyperactivity, anxiety and language delay have been described. However these studies all have design flaws, such as relying on maternal report for child outcome or not controlling for postnatal maternal mood. In a recent study we have recruited women awaiting amniocentesis and followed their child until 18 months. We have found that maternal exposure to antenatal life events was negatively associated with the child’s Bayleys’ Mental Developmental Index (MDI) (rs= – 0.39, p <0.001, n=123). There was also a positive association between antenatal life events and the child’s observed fear reactivity (rs= 0.39, p <0.001, n=106), although the two outcomes were not associated (=-0.09 ,n=108, ns). There were no such associations between postnatal life events and child outcome. This provides new evidence for the occurrence of fetal programming. With both outcomes it was antenatal stress due to problems in the relationship with the partner which had the largest effect on the child. There was an inverse relation between amniotic fluid cortisol level and the child MDI (r= – 0.25, p=0.01, n=125). This is the first evidence in humans that the level of fetal exposure to cortisol in utero is related to the neurodevelopmental outcome of the child. The fetal environment may be altered if stress in the mother changes her hormonal profile; there is a strong correlation between maternal plasma and amniotic fluid cortisol levels (r=0.43 p<0.001, n=290). However many problems remain in understanding the mechanisms. We do not know the gestational age of greatest susceptibility. As pregnancy advances the sensitivity of the maternal HPA axis to stress or anxiety diminishes. It may be that some women maintain a cortisol response to stress depending on their individual genetic constitution, and it is the fetuses of these women that are affected. It may also be that other hormones such as noradrenaline also play a part in mediating links antenatal maternal stress and anxiety and fetal development. It has been suggested that the evolutionary function of fetal programming has been to prepare the child for the particular environment in which he/she is going to find themselves, the predictive adaptive response. Extra vigilance, increased fear reactivity, or readily distracted attention may have been adaptive in a prehistoric stressful environment, but are maladaptive in our society. Acknowledgements: We would like to thank March of Dimes for financial support