Table 1. Distribution of Gestational Age Among Spontaneous and Clinician-Initiated Deliveries: US Singleton Live Births, 2006-2013.
| Gestational Age, wk | Births, No. (%) | |||||||
|---|---|---|---|---|---|---|---|---|
| 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | |
| Spontaneous Delivery | ||||||||
| 20-27 | 5413 (0.7) | 7719 (0.6) | 8841 (0.6) | 8832 (0.6) | 9987 (0.6) | 10 728 (0.6) | 10 839 (0.6) | 10 834 (0.6) |
| 28-31 | 6079 (0.8) | 8817 (0.7) | 9823 (0.7) | 9681 (0.6) | 10 733 (0.6) | 11 708 (0.6) | 12 163 (0.6) | 12 081 (0.6) |
| 32-33 | 8038 (1.0) | 11 612 (0.9) | 13 082 (0.9) | 12 892 (0.9) | 14 413 (0.9) | 15 329 (0.8) | 16 056 (0.8) | 15 966 (0.8) |
| 34-36 | 58 695 (7.4) | 85 896 (6.7) | 98 899 (6.6) | 96 575 (6.3) | 105 899 (6.3) | 114 734 (6.2) | 117 078 (6.1) | 116 307 (6.0) |
| 37-38 | 234 045 (29.4) | 366 813 (28.5) | 431 053 (28.7) | 431 037 (28.3) | 470 228 (28.1) | 508 752 (27.5) | 525 450 (27.4) | 527 207 (27.0) |
| 39-40 | 433 668 (54.4) | 718 367 (55.8) | 839 048 (55.9) | 864 927 (56.8) | 954 969 (57.1) | 1 068 341 (57.8) | 1 115 697 (58.2) | 1 143 430 (58.6) |
| 41 | 46 845 (5.9) | 79 869 (6.2) | 91 067 (6.1) | 90 737 (6.0) | 97 680 (5.8) | 109 853 (6.0) | 112 208 (5.9) | 116 772 (6.0) |
| 42-44 | 4410 (0.6) | 7985 (0.6) | 8295 (0.6) | 7739 (0.5) | 7693 (0.5) | 7769 (0.4) | 7818 (0.4) | 8010 (0.4) |
| Total | 797 193 (100) | 1 287 078 (100) | 1 500 108 (100) | 1 522 420 (100) | 1 671 602 (100) | 1 847 214 (100) | 1 917 309 (100) | 1 950 607 (100) |
| Clinician-Initiated Delivery | ||||||||
| 20-27 | 2889 (0.4) | 4440 (0.5) | 4994 (0.4) | 5232 (0.5) | 5768 (0.4) | 6361 (0.5) | 6913 (0.5) | 7045 (0.5) |
| 28-31 | 5097 (0.8) | 7768 (0.8) | 8639 (0.8) | 8914 (0.8) | 9938 (0.8) | 10 691 (0.8) | 11 014 (0.8) | 11 317 (0.8) |
| 32-33 | 5882 (0.9) | 8831 (0.9) | 9834 (0.9) | 10 039 (0.9) | 11 291 (0.9) | 12 297 (0.9) | 12 224 (0.9) | 12 933 (0.9) |
| 34-36 | 39 315 (6.0) | 58 235 (5.9) | 66 100 (5.8) | 65 603 (5.6) | 71 417 (5.5) | 74 108 (5.3) | 75 808 (5.3) | 77 035 (5.2) |
| 37-38 | 218 944 (33.3) | 318 867 (32.2) | 356 893 (31.5) | 337 054 (28.8) | 339 116 (26.1) | 328 070 (23.3) | 312 275 (21.8) | 306 942 (20.9) |
| 39-40 | 337 754 (51.4) | 516 835 (52.3) | 603 066 (53.3) | 658 450 (56.3) | 766 060 (59.1) | 869 823 (61.8) | 909 255 (63.4) | 938 557 (63.9) |
| 41 | 43 060 (6.6) | 67 521 (6.8) | 76 290 (6.7) | 78 926 (6.7) | 87 360 (6.7) | 99 651 (7.1) | 101 083 (7.0) | 108 360 (7.4) |
| 42-44 | 4188 (0.6) | 6455 (0.7) | 6700 (0.6) | 6266 (0.5) | 6375 (0.5) | 6592 (0.5) | 6308 (0.4) | 6747 (0.5) |
| Total | 657 129 (100) | 988 952 (100) | 1 132 516 (100) | 1 170 484 (100) | 1 297 325 (100) | 1 407 593 (100) | 1 434 880 (100) | 1 468 936 (100) |