Maternal characteristics according to assisted human reproduction (AHR) group and maternal age at delivery*
| Characteristic | No. (%) of non-AHR pregnancies† | No. (%) of AHR pregnancies† | ||||||
|---|---|---|---|---|---|---|---|---|
| < 25 yr n = 73 840 | 25–29 yr n = 140 553 | 30–34 yr n = 166 581 | ≥ 35 yr n = 96 997 | < 25 yr n = 594 | 25–29 yr n = 3455 | 30–34 yr n = 8130 | ≥ 35 yr n = 9730 | |
| Primiparous | 46 087 (62.4) | 66 254 (47.1) | 60 109 (36.1) | 23 796 (24.5) | 352 (59.3) | 2130 (61.6) | 4519 (55.6) | 4992 (51.3) |
| Singletons | 72 329 (98.0) | 136 851 (97.4) | 161 570 (97.0) | 93 722 (96.6) | 544 (91.6) | 2941 (85.1) | 6637 (81.6) | 7668 (78.8) |
| Multiple birth | 1519 (2.1) | 3714 (2.6) | 5027 (3.0) | 3279 (3.4) | 50 (8.4) | 514 (14.9) | 1493 (18.4) | 2062 (21.2) |
| Multiple birth categories | ||||||||
| Twins | 1476 (2.0) | 3621 (2.6) | 4902 (2.9) | 3215 (3.3) | 44 (7.4) | 487 (14.1) | 1381 (17.0) | 1984 (20.4) |
| Triplets | 39 (0.1) | 85 (0.1) | 124 (0.1) | 63 (0.1) | 6 (1.0) | 23 (0.7) | 101 (1.2) | 75 (0.8) |
| Quadruplets | 4 (0) | 8 (0) | 1 (0) | 1 (0) | 0 (0) | 4 (0.1) | 11 (0.1) | 3 (0) |
| Age at delivery, yr, mean ± SD | 21.7 ± 2.0 | 27.2 ± 1.4 | 31.8 ± 1.4 | 37.3 ± 2.3 | 22.5 ± 1.6 | 27.5 ± 1.3 | 32.1 ± 1.3 | 38.3 ± 2.9 |
| Median (IQR) | 22 (20–23) | 27 (26–28) | 32 (31–33) | 37 (36–39) | 23 (22–24) | 28 (27–29) | 32 (31–33) | 38 (36–40) |
| Rural residence at delivery | 26 402 (35.8) | 33 878 (24.1) | 27 970 (16.8) | 13 834 (14.3) | 190 (32.0) | 843 (24.4) | 1224 (15.1) | 958 (9.8) |
| Gestational diabetes | 3170 (4.3) | 8793 (6.3) | 14 325 (8.6) | 12 358 (12.7) | 27 (4.6) | 215 (6.2) | 743 (9.1) | 1279 (13.1) |
| Hypertensive disorders of pregnancy | 6398 (8.7) | 12 627 (9.0) | 14 932 (9.0) | 9580 (9.9) | 49 (8.2) | 334 (9.7) | 859 (10.6) | 1344 (13.8) |
Note: IQR = interquartile range, SD = standard deviation.
↵* The interaction term of age (< 25 yr as reference) by group (non-AHR as reference) was significant at 0.05 in adjusted generalized estimating equation models (Wald Test) for primiparous, multiple v. singleton, rural residence at delivery, hypertensive disorders of pregnancy and age at delivery.
↵† Unless indicated otherwise.