Table 1. Background characteristics of women who had two successive singleton infants without preeclampsia in the first pregnancy and numbers and proportions in the second pregnancy of preterm preeclampsia (<37 weeks of gestation), term preeclampsia and no preeclampsia, Norway1967 to 2012.

(n = 712511).

Characteristics in			Second pregnancy
second pregnancy	Preeclampsia				No preeclampsia
	<37 weeks (n = 1614)		37+ weeks (n = 8409)		(n = 702488)
	n	%	n	%	n	%
Maternal age (years)
<20	7	0.4	49	0.6	7983	1.1
20–24	186	11.5	1370	16.3	154945	22.1
25–29	551	34.1	3155	37.5	281413	40.1
30–34	546	33.8	2689	32.0	193340	27.5
35–39	274	17.0	978	11.6	57323	8.2
40+	50	3.1	168	2.0	7484	1.1
Marital status
married/cohabiting	1518	94.1	7973	94.8	666296	94.8
other	96	5.9	436	5.2	36192	5.2
Smoking*
no	571	70.2	2469	74.1	173636	71.3
occasionally	8	1.0	48	1.4	3680	1.5
daily	86	10.6	319	9.6	27169	11.2
not specified	148	18.2	496	14.9	38920	16.0
Chronic maternal disease
Asthma	62	3.8	278	3.3	16192	2.3
Chronic hypertension	54	3.3	190	2.3	1548	0.2
Chronic renal disease	23	1.4	112	1.3	5839	0.8
Rheumatoid arthritis	10	0.6	29	0.3	1997	0.3
Maternal hearth disease	10	0.6	39	0.5	1962	0.3
Epilepsy	19	1.2	59	0.7	3910	0.6
Thyroid disease	28	1.7	102	1.2	6276	0.9
Body mass index before pregnancy (kg/m2)**
<18.5	3	2.4	7	1.3	1525	3.7
18.5–24.9	47	37.9	210	38.3	25472	61.5
25–29.9	36	29.0	162	29.6	9588	23.1
30+	38	30.6	169	30.8	4843	11.7
Diabetes, all types	84	5.2	240	2.9	5862	0.8
Diabetes mellitus type 1*	24	3.0	43	1.3	939	0.4
Diabetes mellitus type 2*	8	1.0	24	0.7	435	0.2
Gestational diabetes*	18	2.2	96	2.9	2477	1.0
Gestational age (weeks), 1st pregnancy
16–21	18	1.1	57	0.7	1874	0.3
22–27	37	2.3	67	0.8	3128	0.4
28–32	77	4.8	157	1.9	6041	0.9
33–36	194	12.0	537	6.4	28579	4.1
37–44	1288	79.8	7591	90.3	662866	94.4
Birthweight centile, 1st pregnancy
<10	320	19.8	984	11.7	65104	9.3
10–90	1175	72.8	6561	78.0	567427	80.8
>90	109	6.8	836	9.9	69127	9.8
unclassified	10	0.6	28	0.3	830	0.1

*Dec. 1998 to 2012

**2007 to 2012.