Table 1

 Characteristics of pregnant women who underwent in vitro fertilisation (IVF) and women with natural pregnancies between 1990 and 2008, Sweden. Values are numbers (percentages) unless stated otherwise

CharacteristicsIVF pregnancies (n=23 498)Natural pregnancies (n=116 960)
Maternal age at birth:
 19-24322 (1.4)1510 (1.3)
 25-293764 (16.0)18 438 (15.8)
 30-3410 129 (43.1)50 575 (43.2)
 35-398016 (34.1)40 083 (34.3)
 40-471267 (5.4)6354 (5.4)
Mean (SD) age (years)33.3 (4.0)33.4 (3.9)
Median (interquartile range) age (years)33 (31-36)33 (31-36)
Born in Sweden20 267 (86.2)95 180 (81.4)
Prepregnancy body mass index:
 Missing data3961 (16.9)20 228 (17.3)
 <2512 490 (53.2)62 464 (53.4)
 25-295136 (21.9)24 646 (21.1)
 ≥301911 (8.1)9622 (8.2)
Cigarette smoker:
 Missing data1793 (7.6)7731 (6.6)
 No20 130 (85.7)96 996 (82.9)
 Yes1575 (6.7)12 233 (10.5)
Education (years):
 Missing data48 (0.2)1027 (0.9)
 ≤91789 (7.6)11 741 (10.0)
 10-1210 588 (45.1)50 527 (43.2)
 >1211 073 (47.1)53 665 (45.9)
Marital status:
 Missing data1800 (7.7)7798 (6.7)
 Married to or cohabiting with father of child21 569 (91.8)103 882 (88.8)
 Single51 (0.2)3,166 (2.7)
 Other78 (0.3)2114 (1.8)