Sydney, July 20 - Intelligence really begins in the womb which shows up as improved numerical ability and literacy skills in early primary school, according to a new study.

The study shows that healthy foetal growth not only helps improve a child's performance, but may contribute towards closing the achievement gap for children from disadvantaged socio-economic backgrounds.

Director of Perth's Telethon Institute for Child Health Research and study co-author Fiona Stanley said the findings reinforce the need for better integration of health and education policy and services.

'This is an example of the need for joined up thinking; that the pathways into improved education include maternal and child health,' Stanley said.

'We know that drugs like alcohol and tobacco restrict a baby's growth in the womb so we really need to be supporting mothers and giving them the information they need to have healthier pregnancies.