Table 1

Characteristics of 44 552 women by total number of live-birth pregnancies during follow-up (1996 to 2011) participating in the Danish National Birth Cohort

CovariatesNumber of live-birth pregnanciesP value
1 (n=8374)2 (n=25 368)3 (n=9638)≥4 (n=1172)
Age at first live-birth, y (n=44 552)<0.001
 <25 (n=9677)1133 (14)5075 (20)2970 (31)499 (43)
 25–29 (n=22 350)2836 (34)13 542 (54)5415 (56)557 (48)
 ≥30 (n=12 525)4405 (53)6751 (27)1253 (13)116 (10)
Number of induced abortions (n=44 552)<0.001
 0 (n=33 697)5917 (71)19 390 (76)7526 (78)864 (74)
 ≥1 (n=10 855)2457 (29)5978 (24)2112 (22)308 (26)
Number of spontaneous abortions (n=44 552)<0.001
 0 (n=34 964)6802 (81)20 277 (80)7085 (74)800 (68)
 ≥1 (n=9588)1572 (19)5091 (20)2553 (26)372 (32)
Number of stillbirths (n=44 552)<0.001
 0 (n=44 268)8315 (99)25 228 (99)9562 (99)1163 (99)
 ≥1 (n=284)59 (1)140 (1)76 (1)9 (1)
Preterm birth (n=44 552)<0.001
 Ever occurred (n=4436)962 (11)2345 (9)985 (10)144 (12)
 Never occurred (n=40 116)7412 (89)23 023 (91)8653 (90)1028 (88)
Multiple birth (n=44 552)<0.001
 Ever had (n=3664)758 (9)1030 (4)262 (2)43 (4)
 Never had (n=42 459)7616 (91)24 338 (96)9376 (97)1129 (96)
Smoking during pregnancy (n=44 139)<0.001
 Ever smoked (n=2093)2051 (26)4799 (19)1572 (16)227 (19)
 Never smoked (n=35 490)5965 (74)20 517 (81)8063 (84)945 (81)
 Missing (n=413)3585230
Socio-occupational status (n=41 733)<0.001
 High (n=23 171)3881 (50)13 265 (56)5426 (59)599 (55)
 Middle (n=15 154)2923 (38)8913 (37)2973 (33)345 (32)
 Low (n=3408)914 (12)1678 (7)670 (7)146 (13)
 Missing (n=2819)656151256982
Leisure-time exercise during pregnancy, min/week (n=41 820)<0.001
 0 (n=24 607)4821 (62)13 914 (58)5193 (57)679 (62)
 1–180 (n=13 479)2224 (29)7898 (33)3032 (33)325 (30)
 180+ (n=3734)697 (9)2086 (9)859 (9)92 (8)
 Missing (n=2732)632147055476
Alcohol intake before pregnancy, units/week (n=44 552)<0.001
 0 (n=42,32)881 (11)2301 (9)898 (9)152 (13)
 >0–7 (n=32 168)5607 (67)18 610 (73)7121 (74)830 (71)
 >7 (n=8152)1886 (23)4457 (18)1619 (17)190 (16)
Pre-pregnancy BMI before first live-birth (n=40 712)<0.001
 Underweight (n=1827)384 (5)970 (4)397 (5)66 (6)
 Normal weight (n=28 330)5017 (66)16 287 (70)6300 (71)726 (70)
 Overweight (n=7478)1435 (19)4340 (19)1523 (17)180 (17)
 Obese (n=3087)727 (10)1680 (7)608 (7)72 (7)
 Missing (n=3840)8112091810128
  • Underweight, <18.5 kg/m2; normal weight, 18.5 to <25 kg/m2; overweight, 25 to <30 kg/m2; obese, ≥30 kg/m2. Data are n women (% of parity group).

  • BMI, body mass index.