Foetus developmental vulnerability in pre-school children of traumatized antenatal mothers in Cheptais and Mount Elgon Sub-Counties, Bungoma County, Kenya is a study meant to establish the effects of trauma of the mother on the unborn child who was born and now is in pre-school level of education. Through observation by the mother through neonate, infant and childhood stages of developmental milestones in relation to the same observation of non-traumatized mothers, children. Their conclusion is supported by the observation of the same children by their teachers in pre-schools. The sampling strategy involved non-probability where purposive and snow-ball observation, analysis and probability, sampling where multistage or cluster was the most appropriate for observation and units of analysis to make units of representative sample of Cheptais and Mount Elgon subcounties. Majority of the children born to traumatized mothers had developmental problems associated with disabilities as opposed to those mothers who resisted trauma; hence associating trauma with developmental problems.