A new study in Pediatrics says that there is a connection between Autism and pregnancy spacing. In children born less than 36 months apart, there was an increase in Autistic second born children in the pairs overall, but the closer the pregnancies, the higher the number of Autistic children were found. While the researchers say that this is not the first time neurological differences have been found with closely spaced pregnancies, the study will need to be repeated to see if it can be replicated.
Closely spaced pregnancies have been shown to have many potential problems from preterm birth to low birth weight. The theory is that the mother's body is depleted from the original pregnancy, leaving her with a less healthy pregnancy.
Cheslack-Postava K, et al "Closely spaced pregnancies are associated with increased odds of autism in California sibling births" Pediatrics 2011; 127: 246-253.