TABLE 1

Distribution of pre-eclampsia by maternal and child characteristics

Characteristics	Registry linkage^#		MoBa^¶
	n	% pre-eclampsia	n	% pre-eclampsia
Pre-eclampsia
No	390 578		43 281
Yes	16 329	4.0	1747	3.9
Maternal age at delivery years
<25	70 123	4.9	4996	5.5
25–29	137 239	4.1	15 457	4.3
30–34	135 788	3.5	17 300	3.2
35+	63 757	3.9	7275	3.4
Maternal parity
Nulliparous	164 683	5.9	19 511	5.6
1	146 081	2.8	16 045	2.6
2	68 174	2.6	7407	2.4
3+	27 969	2.7	2065	3.0
Maternal education
Less than secondary school	77 340	4.2	3789	4.5
Secondary school	148 773	4.4	14 479	4.4
Up to 4 years of university	137 854	3.9	18 387	3.6
More than 4 years of university	29 950	3.1	8206	3.3
Missing	12 990	2.7	167	5.4
Maternal asthma
No	389 995	4.0	43 199	3.8
Yes	16 912	5.3	1829	5.2
Maternal smoking at start of pregnancy
No	268 177	4.1	39 868	4.0
Yes	72 409	3.4	4968	2.8
Missing	66 321	4.2	192	2.1
Maternal pre-pregnancy BMI
Underweight (<18.5)	NA		1253	2.4
Normal weight (18.5–24.9)	NA		28 421	2.7
Overweight (25–29.9)	NA		9865	5.2
Obese (≥30)	NA		4238	8.7
Missing	NA		1251	4.6
Year of birth
1999	55 155	4.3
2000	54 974	4.2	1102	4.5
2001	52 630	4.1	3265	4.2
2002	51 643	4.3	6878	4.3
2003	52 861	3.7	10 060	3.6
2004	53 459	3.7	10 632	3.9
2005	53 347	3.8	11 828	3.7
2006	32 838	3.9	1263	3.6
Child gender
Male	208 643	4.1	22 975	3.9
Female	198 264	4.0	22 053	3.8
Preterm birth
No	385 458	3.2	42 997	3.1
Yes	21 449	18.0	2031	19.5

There were significant differences in the distribution of pre-eclampsia by all maternal and child characteristics (p<0.003) except for child's sex (p=0.109 in the registry linkage and p=0.639 in MoBa). MoBA: Norwegian Mother and Child Cohort Study; BMI: body mass index. ^#: n=406 907; ^¶: n=45 028.