Table 2.

Odds ratios (95% confidence intervals) for incidence of psychotic disorders in relation to prenatal and perinatal characteristics. Values derived from conditional logistic regression model

	Schizophrenia (n=163)	Affective psychosis (n=193)	Reactive psychosis (n=281)
Maternal factors
Age at delivery (years):
⩽19	0.8 (0.4 to 1.7)	1.0 (0.5 to 2.0)	1.3 (0.8 to 2.2)
20-29*	1.0	1.0	1.0
⩾30	1.2 (0.8 to 1.8)	1.4 (0.9 to 2.0)	1.3 (0.9 to 1.8)
Parity:
1	1.3 (0.9 to 1.9)	1.0 (0.7 to 1.4)	1.1 (0.9 to 1.5)
2-3*	1.0	1.0	1.0
4	2.0 (1.0 to 3.8)†	1.0 (0.5 to 2.2)	2.1 (1.3 to 3.5)
Pregnancy and delivery factors
Hypertensive diseases	1.3 (0.6 to 3.1)	1.6 (0.7 to 3.5)	0.8 (0.4 to 1.7)
Diabetes	7.8 (0.9 to 67.6)	0.7 (0.1 to 6.8)	3.4 (0.5 to 21.5)
Bleeding during pregnancy	3.5 (1.2 to 10.3)	1.1 (0.4 to 2.9)	1.2 (0.5 to 3.0)
Uterine atony	1.4 (0.7 to 2.6)	2.2 (1.2 to 4.1)	1.0 (0.6 to 1.8)
Child characteristics
Birth weight for gestational age:
Small (⩾2 SD below mean)	1.5 (0.7 to 3.1)†	1.3 (0.7 to 2.7)	1.0 (0.6 to 1.7)
Mean*	1.0	1.0	1.0
Large (⩾2 SD above mean)	0.5 (0.2 to 1.6)	1.2 (0.5 to 2.9)	0.9 (0.4 to 2.0)†
Ponderal index (centiles)‡:
⩽5	2.1 (0.8 to 4.3)	0.6 (0.3 to 1.4)	1.1 (0.6 to 2.0)
6-94*	1.0	1.0	1.0
⩾95	1.0 (0.4 to 2.2)	1.0 (0.5 to 2.2)	1.4 (0.8 to 2.5)
Apgar score at 1 minute:
0-6	0.97 (0.4 to 2.3)	1.3 (0.6 to 2.7)	1.8 (0.9 to 3.7)
7-10*	1.0	1.0	1.0
Asphyxia	1.0 (0.6 to 1.8)	1.4 (0.9 to 2.3)	0.8 (0.5 to 1.3)
Season of birth
January-April	1.4 (1.0 to 2.0)	1.5 (1.1 to 2.0)	1.2 (0.9 to 1.5)
May-December*	1.0	1.0	1.0

^*Reference category. 

^†Significant interaction with sex (P<0.05). 

^‡(100×(birth weight (g))/(birth length (cm))³. Entered in a separate model in place of birth weight for gestational age.