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Table 1 Changes in population characteristics and small-for-gestational age (SGA) rates in the United States 1990–1992, 2002–2004, 2008–2010

From: The association between temporal changes in the use of obstetrical intervention and small- for-gestational age live births

Characteristic 1990–1992 2002–04 2008–10
  All live births SGA All live births SGA All live births SGA
  No. (%) No. (rate/100) No. (%) No. (rate/100) No. (%) No. (rate/100)
Age <20 years 1,266,799 (13.1) 178,826 (14.1) 1,088,005 (10.8) 143,644 (13.2) 1,190,869 (10.1) 156,115 (13.1)
 20–24 years 2,565,257 (26.6) 285,798 (11.1) 2,611,711 (25.9) 272,080 (10.4) 2,900,487 (24.6) 307,631 (10.6)
 25–29 years 2,890,561 (29.9) 260,847 (9.0) 2,699,395 (26.8) 214,646 (8.0) 3,346,378 (28.4) 279,361 (8.3)
 30–34 years 2,069,631 (21.4) 174,713 (8.4) 2,345,977 (23.3) 162,548 (6.9) 2,721,282 (23.1) 202,789 (7.5)
 35–39 years 747,403 (7.7) 66,494 (8.9) 1,097,056 (10.9) 82,088 (7.5) 1,335,357 (11.3) 101,957 (7.6)
 ≥40 years 117,194 (1.2) 11,932 (10.2) 239,552 (2.4) 21,858 (9.1) 311,398 (2.6) 27,668 (8.9)
Non-Hispanic White 6,636,243 (68.7) 540,896 (8.2) 6,132,920 (60.8) 438,101 (7.1) 6,359,020 (53.9) 471,413 (7.4)
Non-Hispanic Black 1,700,294 (17.6) 291,888 (17.2) 1,559,920 (15.5) 231,876 (14.9) 1,731,740 (14.7) 262,800 (15.2)
Hispanic 992,365 (10.3) 106,957 (10.8) 1,857,538 (18.4) 167,041 (9.0) 2,901,453 (24.6) 248,242 (8.6)
Other 327,943 (3.4) 38,869 (11.9) 531,318 (5.3) 59,846 (11.3) 813,558 (6.9) 93,066 (11.4)
Low education 2,007,942 (21.7) 289,581 (14.4) 2,061,474 (20.7) 246,226 (11.9) 2,340,804 (20.1) 266,128 (11.4)
Mother not married 2,756,978 (28.6) 416,329 (15.1) 3,548,727 (35.2) 434,968 (12.3) 4,850,493 (41.1) 568,102 (11.7)
Maternal smoking 1,504,155 (17.7) 264,893 (17.6) 1,112,652 (11.3) 174,247 (15.7) 984,727 (9.5) 156,269 (15.9)
Nulliparous 3,160,790 (32.9) 368,815 (11.7) 3,339,247 (33.3) 365,533 (10.9) 4,000,839 (34. 3) 450,705 (11.3)
Nulliparous, ≥35 years 118,162 (1.2) 14,550 (12.3) 209,556 (2.1) 22,694 (10.8) 266,465 (2.3) 29,673 (11.1)
Labour induced 1,097,842 (11.4) 99,493 (9.1) 2,315,760 (23.0) 199,300 (8.6) 2,800,695 (23.7) 263,567 (9.4)
Cesarean delivery 2,100,393 (21.8) 216,111 (10.3) 2,631,066 (26.1) 248,880 (9.5) 3,674,107 (31.1) 349,172 (9.5)
Infant sex (male) 4,942,269 (51.2) 397,264 (8.0) 5,160,195 (51.2) 359,953 (7.0) 6,042,020 (51.2) 427,464 (7.1)
Gest. age <32 weeks 106,575 (1.1) 7926 (7.4) 112,312 (1.1) 10,745 (9.6) 125,037 (1.1) 12,083 (9.7)
 32–33 weeks 82,200 (0.9) 11,889 (14.5) 91,770 (0.9) 14,557 (15.9) 102,715 (0.9) 17,192 (16.7)
 34–36 weeks 478,843 (5.0) 77,605 (16.2) 637,780 (6.3) 90,439 (14.2) 721,151 (6.1) 105,742 (14.7)
 37–38 weeks 1,721,215 (17.8) 206,315 (12.0) 2,763,381 (27.4) 262,380 (9.5) 3,339,299 (28.3) 337,035 (10.1)
 39–40 weeks 5,712,036 (59.2) 580,887 (10.2) 5,581,621 (55.4) 470,764 (8.4) 6,698,762 (56.7) 559,528 (8.4)
 41 weeks 1,160,789 (12.0) 73,403 (6.3) 805,794 (8.0) 43,635 (5.4) 760,526 (6.4) 40,911 (5.4)
 ≥42 weeks 395,187 (4.1) 20,585 (5.2) 89,038 (0.9) 4344 (4.9) 58,281 (0.5) 3030 (5.2)
Total 9,656,845 (100) 978,610 (10.1) 10,081,696 (100) 896,864 (8.9) 11,805,771 (100) 1,075,521 (9.1)
  1. Low education denotes less than high school education. Gestational age-specific SGA rates were calculated using the traditional approach (per 100 live births in that gestational age category)