Table 3. Subgroup analysis of the association between HDP and ASD.

	Studies	OR	95% CI
Clinical classification
Gestational hypertension	9	1.37	1.21–1.54
Pre-eclampsia	11	1.43	1.31–1.55
Chronic hypertension complicating pregnancy	4	1.48	1.29–1.70
Mixed	3	1.37	1.13–1.67
Maternal age
Higher in the case group	7	1.44	1.33–1.55
Match between case and control	7	1.29	1.11–1.50
Lower in the control group	2	1.42	1.16–1.73
Not mentioned	4	1.50	1.22–1.84
Preterm birth
Higher rate in the case group	7	1.41	1.22–1.63
Match between case and control	3	1.78	1.33–2.37
Higher rate in the control group	1	1	0.51–1.95
Not mentioned	10	1.41	1.32–1.51
Premature rupture of membranes
Higher rate in the case group	1	0.82	0.18–3.76
Match between case and control	3	0.92	0.66–1.28
Higher rate in the control group	1	1	0.51–1.95
Not mentioned	16	1.45	1.36–1.54
Maternal education
Higher in the case group	1	3.65	1.08–12.35
Match between case and control	3	1.90	1.57–2.31
Higher in the control group	2	1.26	0.80–1.99
Not mentioned	15	1.38	1.30–1.47
Geographic area
Asia	3	1.18	0.70–1.99
America	10	1.45	1.36–1.54
Europe	6	1.46	1.16–1.84
Africa	1	1.78	0.40–7.90
Oceania	2	1.17	0.94–1.45
Gender of participants
Male/female higher in case group	8	1.38	1.29–1.48
Match	9	1.68	1.42–1.99
Male/female higher in control group	0	-	-
Not mentioned	4	1.44	1.19–1.74

The mixed group include pre-eclampsia, gestational hypertension and chronic hypertension complicating pregnancy.