TABLE 1—
Odds Ratios (ORs) and 95% Confidence Intervals (CIs) for Having a Small-for-Gestational-Age Infant, by Potential Confounding Variable: Workers Giving Birth Between January 1997 and March 1999, Québec, Canada
| Case Mothers (N = 1536), No.a (%) | Control Mothers (N = 4441), No.a (%) | OR (95% CI) | |
| Maternal smoking, 3rd trimester, cigarettes/d | |||
| 0b | 924 (60.2) | 3679 (83.0) | 1.0 |
| 1–9 | 224 (14.6) | 287 (6.5) | 3.1 (2.6, 3.8) |
| 10–19 | 291 (19.0) | 369 (8.3) | 3.1 (2.7, 3.7) |
| ≥20 | 96 (6.3) | 100 (2.3) | 3.8 (2.9, 5.1) |
| Congenital anomaly | |||
| Nob | 1490 (97.0) | 4384 (98.7) | 1.0 |
| Yes | 46 (3.0) | 57 (1.3) | 2.4 (1.6, 3.5) |
| Maternal caffeine consumption, 3rd trimester, portions/wkc | |||
| 0b | 362 (23.6) | 1328 (29.9) | 1.0 |
| > 0–4 | 332 (21.6) | 1153 (26.0) | 1.1 (0.9, 1.3) |
| 5–9 | 368 (24.0) | 1098 (24.8) | 1.2 (1.0, 1.5) |
| 10–14 | 214 (14.0) | 425 (9.6) | 1.8 (1.5, 2.3) |
| ≥15 | 258 (16.8) | 432 (9.7) | 2.2 (1.8, 2.7) |
| Maternal alcohol consumption, 3rd trimester, drinks/wk | |||
| 0b | 1109 (72.3) | 3169 (71.5) | 1.0 |
| > 0–2 | 389 (25.4) | 1221 (27.5) | 0.9 (0.8, 1.0) |
| > 2 | 36 (2.4) | 45 (1.0) | 2.3 (1.5, 3.6) |
| Maternal education, y | |||
| ≥17b | 321 (20.9) | 1337 (30.2) | 1.0 |
| 14–16 | 464 (30.3) | 1498 (33.8) | 1.3 (1.1, 1.5) |
| 12–13 | 581 (37.9) | 1284 (29.0) | 1.9 (1.6, 2.2) |
| < 12 | 168 (11.0) | 313 (7.1) | 2.2 (1.8, 2.8) |
| Age of children at home, mean, y | |||
| No children | 940 (61.2) | 2193 (49.4) | 1.8 (1.6, 2.1) |
| ≤6b | 471 (30.7) | 2009 (45.3) | 1.0 |
| > 6 | 125 (8.1) | 238 (5.4) | 2.2 (1.8, 2.8) |
| Mother’s height, cm | |||
| 170–188b | 172 (11.2) | 862 (19.5) | 1.0 |
| 163–169 | 572 (37.3) | 1898 (42.8) | 1.5 (1.3, 1.8) |
| 157–162 | 496 (32.3) | 1168 (26.4) | 2.1 (1.8, 2.6) |
| 105–156 | 294 (19.2) | 504 (11.4) | 2.9 (2.3, 3.6) |
| Mother’s body mass index, kg/m2 | |||
| 25–61b | 271 (17.7) | 1110 (25.1) | 1.0 |
| 22–24 | 383 (25.0) | 1318 (29.8) | 1.2 (1.0, 1.4) |
| 20–21 | 440 (28.7) | 1157 (26.1) | 1.6 (1.3, 1.9) |
| 14–19 | 439 (28.6) | 842 (19.0) | 2.1 (1.8, 2.6) |
| Father’s height, cm | |||
| 186–206b | 53 (3.5) | 278 (6.3) | 1.0 |
| 178–185 | 596 (39.0) | 2049 (46.4) | 1.5 (1.1, 2.1) |
| 173–177 | 408 (26.7) | 1134 (25.7) | 1.9 (1.4, 2.6) |
| 152–172 | 473 (30.9) | 957 (21.7) | 2.6 (1.9, 3.5) |
| Family income, Can $/y | |||
| ≥50 000b | 452 (29.4) | 1721 (38.8) | 1.0 |
| 35 000–49 999 | 410 (26.7) | 1183 (26.6) | 1.3 (1.1, 1.5) |
| < 35 000 | 633 (41.2) | 1433 (32.3) | 1.7 (1.5, 1.9) |
| Unknown | 41 (2.7) | 104 (2.3) | 1.5 (1.0, 2.2) |
| Partner’s employment status | |||
| Employedb | 1396 (90.9) | 4141 (93.3) | 1.0 |
| Unemployed | 78 (5.1) | 149 (3.4) | 1.6 (1.2, 2.1) |
| No partner | 61 (4.0) | 150 (3.4) | 1.2 (0.9, 1.6) |
| Previous pregnancies, no. | |||
| 0b | 804 (52.3) | 1811 (40.8) | 1.0 |
| 1–3 | 681 (44.3) | 2524 (56.8) | 0.6 (0.5, 0.7) |
| > 3 | 51 (3.3) | 106 (2.4) | 1.1 (0.8, 1.5) |
| Previous adverse pregnancy outcomes, no. | |||
| 0b | 1124 (73.2) | 3354 (75.5) | 1.0 |
| 1 | 282 (18.4) | 815 (18.4) | 1.0 (0.9, 1.2) |
| ≥2 | 130 (8.5) | 272 (6.1) | 1.4 (1.2, 1.8) |
| Mother’s age, y | |||
| < 25 | 334 (21.7) | 806 (18.1) | 1.3 (1.1, 1.5) |
| 25–34b | 1000 (65.1) | 3154 (71.0) | 1.0 |
| ≥35 | 202 (13.2) | 481 (10.8) | 1.3 (1.1, 1.6) |
| Mother’s involvement in family responsibilities | |||
| No childrenb | 948 (61.8) | 2208 (49.8) | 1.0 |
| < 50% | 71 (4.6) | 205 (4.6) | 0.8 (0.6, 1.1) |
| ≥50% | 515 (33.6) | 2017 (45.5) | 0.6 (0.5, 0.7) |
| Physical activity before pregnancy, times/mod | |||
| 0b | 1075 (70.0) | 2907 (65.6) | 1.0 |
| ≥1 | 460 (30.0) | 1525 (34.4) | 0.8 (0.7, 0.9) |
| Gestational diabetes | |||
| Nob | 1452 (94.5) | 4141 (93.2) | 1.0 |
| Yes | 84 (5.5) | 300 (6.8) | 0.8 (0.6, 1.0) |
| Chronic hypertension | |||
| Nob | 1525 (99.3) | 4396 (99.0) | 1.0 |
| Yes | 11 (0.7) | 44 (1.0) | 0.7 (0.4, 1.4) |
| Other chronic diseasee | |||
| Nob | 1472 (95.8) | 4287 (96.5) | 1.0 |
| Yes | 64 (4.2) | 154 (3.5) | 1.2 (0.9, 1.6) |
| White ethnicity | |||
| Yesb | 1514 (98.6) | 4383 (98.9) | 1.0 |
| No | 21 (1.4) | 49 (1.1) | 1.2 (0.7, 2.1) |
| Passive smoking, 3rd trimesterf | 1533 | 4432 | 1.1 (1.1, 1.1) |
| Illicit drug use during pregnancyg | |||
| Nob | 1523 (99.2) | 4418 (99.5) | 1.0 |
| Yes | 12 (0.8) | 22 (0.5) | 1.6 (0.8, 3.2) |
a Totals vary because of missing data.
bReference category.
cOne cup of coffee = 1 portion; 1 cup of tea = 0.76 portion; 1 glass of cola = 0.44 portion.
dActivity was defined as 20 to 30 minutes of moderate- to high-intensity activity.
eExamples of other chronic diseases are asthma, thyroid disorder, bowel inflammatory disease, hypoglycemia, kidney disease, heart diseases, epilepsy, and hypercholesterolemia.
fHere the variable was number of cigarettes smoked per day in the presence of the pregnant woman when she was not at work; OR represents the SGA risk variation for each additional cigarette per day, because this variable was continuous in the model.
gExamples of illicit drugs are marijuana, hashish, cocaine, heroin, amphetamines, LSD, phencyclidine (PCP), and mescaline.