Table 1.

Characteristics of the study population (n = 1163)

	Study cohort Number (%)	Used hormonal contraceptives before first birth
		%	p value
Age
35–36 years	320 (15.4)	49.1
37–38 years	273 (13.1)	49.5
39–40 years	276 (13.3)	42.4
41–42 years	296 (14.2	27.4
43–44 years	260 (12.5)	20.4
45–46 years	296 (14.2)	15.5
4949 years	357 (17.2)	10.9	p < 0.0001
Age at menarche
< = 12 year	538 (26.4)	30.1
13 years	615 (30.2)	35.5
> = 14 years	882 (43.3)	26.6	p = 0.001
Age at first birth
<= 20 years	503 (24.2)	6.4
21–25 years	961 (46.3)	25.6
> = 26 years	614 (29.5)	57.0	p<= 0.0001
Weight of newborn child
-3000 g	360 (18.0)	31.4
30001–3500 g	750 (37.4)	31.2
3501–4000 g	617 (30.8)	28.4
> = 4001 g	276 (13.8)	31.9	P = 0.6
Education
7–9 years	428 (20.9)	12.9
10–12 years	759 (37.2)	24.2
13–15 years	517 (25.3)	39.9
> = 16 years	339 (16.6)	51.9	p < 0.0001
Years between menarche and first birth
0–5 years	215(10.6)	5.6
6–10 years	926(45.5)	17.4
11–15 years	628 (30.9)	43.0
> = 16 years	266 (13.1)	64.7	p < 0.0001
Number of births
One	307(14.8)	46.3
Two	1044 (50.2)	32.2
Three	543 (26.1)	23.9
> = Four	184(8.9)	10.9	p < 0.0001
Smoking in the first pregnancy
No	1396 (69.6)	30.5
Yes	611 (30.4)	30.0	p = 0.8