Table 1.

Litters are rarely used as the statistical unit in NDD publications

Category	Search criteria	Number of litters indicated	Litter treated as statistical unit
Genetic (including molecular studies of brain development)	(SCN2A AND Autism) OR (CHD8 AND Autism) OR (UBE3A AND Angelman)	2/45 (4%)	0/45 (0%)
	neocortex AND development AND regulation	3/29 (10%)	1/29 (3%)
	(embryonic knockout OR electroporation) AND brain development	4/25 (16%)	1/25 (4%)
Genetic total		9/99 (9%)	2/99 (2%)
Environment	maternal immune activation AND autism	23/33 (67%)	6/33 (18%)
	autism AND air pollution	8/9 (89%)	3/9 (33%)
	BPA AND brain development	8/9 (89%)	4/9 (44%)
	autism AND VPA	30/66 (45%)	10/66 (15%)
Environment total		69/117 (59%)	23/117 (20%)