Table 1 Characteristics of the study population, Manitoba, Canada, 1980-2016a
From: Revisiting the association between maternal and offspring preterm birth using a sibling design
| Â | Population Cohort | Mothers without sisters | Mothers with sisters | ||||
|---|---|---|---|---|---|---|---|
Discordant sisters | Concordant sisters | ||||||
Mother Born Preterm | Mother Born at term | Index mothers born preterm with sisters born at term | Index mothers born at term with sisters born preterm | All born preterm | All born at term | ||
Number of mothers (%)b | 39,573 (100.0) | 1328 (3.4) | 26,805 (67.7) | 455 (1.2) | 578 (1.5) | 69 (0.2) | 10,338 (26.1) |
Number of infants (%)b | 79,198 (100.0) | 2565 (3.2) | 50,647 (63.9) | 1069 (1.4) | 1430 (1.8) | 137 (0.2) | 23,350 (29.5) |
Infant’s preterm birth | 4913 (6.2) | 198 (7.7) | 3025 (6.0) | 109 (10.2) | 143 (10.0) | 18 (13.1) | 1420 (6.1) |
Infant’s preterm birth type | |||||||
 Provider-initiated | 1489 (1.9) | 44 (1.7) | 912 (1.8) | 34 (3.2) | 53 (3.7) | < 6c | 443 (1.9) |
 Spontaneous | 3424 (4.3) | 154 (6.0) | 2113 (4.2) | 75 (7.0) | 90 (6.3) | c | 977 (4.2) |
Infant’s Birth Year, mean(SD) | 2010 (4.3) | 2010 (4.4) | 2010 (4.3) | 2010 (4.2) | 2009 (4.4) | 2009 (4.3) | 2010 (4.2) |
Male infant | 40,624 (51.3) | 1290 (50.3) | 26,037 (51.4) | 547 (51.2) | 765 (53.5) | 70 (51.1) | 11,915 (51.0) |
Infant’s Birth Order | |||||||
 1 | 39,069 (49.3) | 1321 (51.5) | 26,495 (52.3) | 449 (42.0) | 567 (39.7) | 67 (48.9) | 10,170 (43.6) |
 2 | 22,505 (28.4) | 727 (28.3) | 14,559 (28.8) | 281 (26.3) | 374 (26.1) | 42 (30.7) | 6522 (27.9) |
 3 | 9930 (12.5) | 299 (11.7) | 5727 (11.3) | 165 (15.4) | 212 (14.8) | 17 (12.4) | 3510 (15.0) |
 4+ | 7694 (9.7) | 218 (8.5) | 3866 (7.6) | 174 (16.3) | 277 (19.4) | 11 (8.0) | 3148 (13.5) |
Mother’s Age | |||||||
  < 20 | 17,467 (22.1) | 504 (19.6) | 10,306 (20.3) | 251 (23.5) | 422 (29.5) | 29 (21.2) | 5955 (25.5) |
 20–24 | 28,714 (36.3) | 915 (35.7) | 17,654 (34.9) | 438 (41.0) | 581 (40.6) | 51 (37.2) | 9075 (38.9) |
 25–29 | 23,741 (30.0) | 812 (31.7) | 15,856 (31.3) | 281 (26.3) | 321 (22.5) | 38 (27.7) | 6433 (27.6) |
 30 + | 9276 (11.7) | 334 (13.0) | 6831 (13.5) | 99 (9.7) | 106 (7.4) | 19 (13.9) | 1887 (8.1) |
Neighborhood SES tertiles | |||||||
 P0-P33 (Lowest SES) | 25,940 (32.8) | 753 (29.4) | 13,341 (26.3) | 560 (52.4) | 794 (55.5) | c | 10,444 (44.7) |
 P34-P66 | 25,244 (31.9) | 870 (33.9) | 16,983 (33.5) | 298 (27.9) | 373 (26.1) | 57 (41.6) | 6663 (28.5) |
 P67-P100 (Highest SES) | 25,219 (31.8) | 846 (33.0) | 18,266 (36.1) | 197 (18.4) | 240 (16.8) | 27 (19.7) | 5643 (24.2) |
 Unknown | 2795 (3.5) | 96 (3.7) | 2057 (4.1) | 14 (1.3) | 23 (1.5) | < 6 c | 600 (2.6) |
Location of Neighborhood | |||||||
 Urban | 35,674 (45.0) | 1364 (53.2) | 25,017 (49.4) | 398 (37.2) | 514 (35.9) | 75 (54.7) | 8306 (35.6) |
 Rural South | 17,364 (21.9) | 483 (18.8) | 11,079 (21.9) | 196 (18.3) | 246 (17.2) | 22 (16.1) | 5338 (22.9) |
 Rural Mid | 11,891 (15.0) | 362 (14.1) | 7378 (14.6) | 182 (17.0) | 237 (16.6) | 22 (16.1) | 3710 (15.9) |
 Rural North | 14,269 (18.0) | 356 (13.9) | 7173 (14.2) | 293 (27.4) | 433 (30.3) | 18 (13.1) | 5996 (25.7) |
Mother moved in Year before Birth of Child | 20,819 (26.3) | 728 (28.4) | 13,518 (26.7) | 295 (27.6) | 378 (26.4) | 34 (24.8) | 5866 (25.1) |
Mother had a Substance Abuse Diagnosis in Year before Birth of Child | 2111 (2.7) | 67 (2.6) | 1174 (2.3) | 37 (3.5) | 67 (4.7) | < 6 c | 761 (3.3) |
Mother had no partnerd | 6400 (8.52) | 220 (8.92) | 4120 (8.55) | 83 (8.84) | 113 (9.28) | 11 (9.65) | 1853 (8.70) |
Mother smoked during pregnancyd | 19,257 (26.0) | 688 (27.91) | 11,435 (23.74) | 317 (33.76) | 438 (35.96) | 34 (29.82) | 6345 (29.78) |
Inadequate prenatal cared | 13,548 (18.26) | 406 (16.47) | 7270 (15.09) | 271 (28.86) | 378 (31.03) | 22 (19.30) | 5201 (24.41) |
Employment income assistance d | 15,631 (21.06) | 578 (23.45) | 9383 (19.48) | 334 (27.42) | 246 (26.20) | 32 (28.07) | 5058 (23.74) |
Maternal educationd | |||||||
 12 years or less | 17,692 (23.84) | 541 (21.95) | 9829 (20.40) | 336 (35.78) | 481 (39.49) | 20 (17.54) | 6485 (30.44) |
 More than 12 years | 42,885 (57.79) | 1496 (60.69) | 30,512 (63.34) | 379 (40.36) | 426 (34.98) | 80 (70.18) | 9992 (46.90) |
 Unknown | 13,637 (18.38) | 428 (17.36) | 7831 (16.26) | 224 (23.86) | 311 (25.53) | 14 (12.28) | 4829 (22.66) |