Table 1.

Characteristics of pregnancies excluding births in Oslo and Troms counties.

Characteristic	Category	No PE	PE and gestation $\text{length}\ge 37\mathrm{wk}$	PE and gestation $\text{length}<37\mathrm{wk}$
Total N		460,534	14,044	4,383
Average maternal age (y)		29.2	28.6	29.1
Sex of baby [$n$ (%)]	Male	236,400 (51.3)	7,364 (52.4)	2,120 (48.4)
	Female	224,097 (48.7)	6,680 (47.6)	2,261 (51.6)
	Missing	37 (00.0)	0 (00.0)	2 (0.00)
Region[$n$ (%)]	Southeast	236,933 (51.4)	7,115 (50.7)	2,384 (54.4)
	North	49,585 (10.8)	1,638 (11.7)	505 (11.5)
	West coast	173,420 (37.7)	5,274 (37.6)	1,485 (33.9)
	Missing	596 (0.1)	17 (0.1)	9 (0.2)
Maternal smoking [$n$ (%)]	Nonsmoker	296,552 (64.4)	9,479 (67.5)	2,861 (65.3)
	Quit during pregnancy	21,485 (4.7)	827 (5.9)	210 (4.8)
	Smoked throughout	44,389 (9.6)	872 (6.2)	299 (6.8)
	Missing	98,108 (21.3)	2,866 (20.4)	1,013 (23.1)
Mother’s education [$n$ (%)]	0 – 9 y	77,481 (16.8)	2,430 (17.3)	811 (18.5)
	10 – 14 y	160,971 (35)	5,356 (38.1)	1,676 (38.2)
	$\ge 15\text{y}$	197,465 (42.9)	5,741 (40.9)	1,707 (38.9)
	Missing	24,617 (5.3)	517 (3.7)	189 (4.3)
Parity [$n$ (%)]	Parous	256,674 (55.7)	5,214 (37.1)	1,623 (37)
	Primiparous	203,860 (44.3)	8,830 (62.9)	2,760 (63)
Mother's birth country [$n$ (%)]	Other	79,116 (17.2)	1,824 (13)	688 (15.7)
	Norway	379,183 (82.3)	12,190 (86.8)	3,608 (82.3)
	Missing	2,235 (0.5)	30 (0.2)	87 (2)
Married or living together as married [$n$ (%)]	No	36,012 (7.8)	1,215 (8.7)	394 (9)
	Yes	424,522 (92.2)	12,829 (91.3)	3,989 (91)