Table 1.
Characteristics of the study population by BMI categories
| Characteristics |
Total (N = 45,824) |
Underweight BMI <18.50 N = 4,348 (9.5%) |
Normal BMI 18.50-24.99 N = 31,555 (68.9%) |
Overweight BMI 25.00-29.99 N = 6,961 (15.2%) |
Obese BMI ≥ 30.00 N = 2,960 (6.5%) |
|
|---|---|---|---|---|---|---|
| N (%) | N (%) | N (%) | N (%) | N (%) | p-value | |
| Mean Age (SD) |
24.1 (6.0) |
22.4 (5.2) |
23.4 (5.7) |
26.3 (6.5) |
28.1 (6.6) |
<0.0001 |
| Marital |
|
|
|
|
|
<0.0001 |
| Single |
7075 (15.4) |
794 (18.3) |
5089 (16.1) |
874 (12.6) |
318 (10.7) |
|
| Married |
34913 (76.2) |
3220 (74.1) |
24004 (76.1) |
5416 (77.8) |
2273 (76.8) |
|
| Other |
3834 (8.4) |
334 (7.7) |
2460 (7.8) |
671 (9.6) |
369 (12.5) |
|
| Missing |
2 (0.0) |
0 (0.0) |
2 (0.0) |
0 (0.0) |
0 (0.0) |
|
| Education |
|
|
|
|
|
<0.0001 |
| Less than High School |
26066 (56.9) |
2528 (58.1) |
17193 (54.5) |
4329 (62.2) |
2016 (68.1) |
|
| High School |
13753(30.0) |
1311 (30.2) |
9662 (30.6) |
2019 (29.0) |
761 (25.7) |
|
| More than High School |
5204 (11.4) |
432 (9.9) |
4146 (13.1) |
491 (7.1) |
135 (4.6) |
|
| Missing |
801(1.8) |
77 (1.8) |
554 (1.8) |
122 (1.8) |
48 (1.6) |
|
| Race |
|
|
|
|
|
<0.0001 |
| White |
20341 (44.4) |
2009 (46.2) |
14768 (46.8) |
2568 (36.9) |
996 (33.7) |
|
| Black |
22231 (48.5) |
1989 (45.8) |
14538 (46.1) |
3896 (56.0) |
1808 (61.1) |
|
| Other |
3071 (6.7) |
296 (6.8) |
2126 (6.7) |
495 (7.1) |
154 (5.2) |
|
| Missing |
181 (0.4) |
54 (1.2) |
123 (0.4) |
2 (0.0) |
2 (0.1) |
|
| SES Index |
|
|
|
|
|
<0.0001 |
| 0.0-3.9 |
17850 (39.0) |
1803 (41.5) |
11619 (36.8) |
3016 (43.3) |
1412 (47.7) |
|
| 4.0-5.9 |
13967 (30.5) |
1295 (29.8) |
9371 (29.7) |
2033 (32.8) |
998 (33.7) |
|
| 6.0-9.5 |
12830 (28.0) |
1138 (26.2) |
9764 (30.9) |
1456 (20.9) |
472 (16.0) |
|
| Missing |
1177 (2.6) |
112 (2.6) |
801 (2.5) |
186 (2.7) |
78 (2.6) |
|
| Tobacco use |
21154 (46.2) |
2257 (51.9) |
14819(47.0) |
2907 (41.8) |
1171 (39.6) |
<0.0001 |
| Missing |
280 (0.6) |
23 (0.5) |
192 (0.6) |
39 (0.6) |
26 (0.9) |
|
| Substance use |
50 (0.1) |
1 (0.0) |
43 (0.1) |
5 (0.1) |
1 (0.0) |
0.2416 |
| Missing |
283 (0.6) |
24 (0.6) |
195 (0.6) |
45 (0.7) |
19 (0.6) |
|
| Parity |
|
|
|
|
|
<0.0001 |
| Primiparous |
13028 (28.4) |
1567 (36.0) |
10010 (31.7) |
1121 (16.1) |
330 (11.2) |
|
| Multiparous |
32635 (71.2) |
2758 (63.4) |
21439 (67.9) |
5816 (83.6) |
2622 (88.6) |
|
| Missing |
161 (0.4) |
23 (0.5) |
106 (0.3) |
24 (0.3) |
8 (0.3) |
|
| Previous Premature infant |
|
|
|
|
|
<0.0001 |
| Previous Preterm birth |
7602 (16.6) |
874 (20.1) |
4915(15.6) |
1218 (17.5) |
595 (20.1) |
|
| Previous Full-term birth |
25054 (54.7) |
1885 (43.4) |
16537 (52.4) |
4604 (66.1) |
2028 (68.5) |
|
| No Previous births |
13067 (28.5) |
1577 (36.3) |
10037 (31.8) |
1122 (16.1) |
331 (11.2) |
|
| Missing |
101 (0.2) |
12 (0.3) |
66 (0.2) |
17 (0.2) |
6 (0.2) |
|
| Number of Prenatal Visits |
|
|
|
|
|
<0.0001 |
| 1-5 |
10158 (22.2) |
1016 (23.4) |
6903 (21.9) |
1514 (21.8) |
725 (24.5) |
|
| 6-9 |
16326 (35.6) |
1611 (37.1) |
11171 (35.4) |
2495 (35.8) |
1049 (35.4) |
|
| 10-14 |
15854 (34.6) |
1445 (33.2) |
11036 (35.0) |
2428 (34.8) |
945 (31.9) |
|
| 15 and above |
3446 (7.5) |
270 (6.2) |
2421 (7.7) |
515 (7.4) |
240 (8.1) |
|
| Missing |
40 (0.1) |
6 (0.1) |
24 (0.1) |
9 (0.1) |
1 (0.0) |
|
| Diabetes |
223 (0.5) |
15 (0.3) |
97 (0.3) |
54 (0.8) |
57 (1.9) |
<0.0001 |
| Missing |
256 (0.6) |
28 (0.6) |
173 (0.6) |
37 (0.5) |
18 (0.6) |
|
| Hypertension |
2172 (4.7) |
101 (2.3) |
1062 (3.4) |
503 (7.2) |
506 (17.1) |
<0.0001 |
| Missing |
94 (0.2) |
5 (0.1) |
67 (0.2) |
14 (0.2) |
8 (0.3) |
|
| Anemia |
9153 (20.0) |
980 (22.5) |
6366 (20.2) |
1323 (19.0) |
484 (16.4) |
<0.0001 |
| Missing |
222 (0.5) |
21 (0.5) |
152 (0.5) |
34 (0.5) |
15 (0.5) |
|
| Preelampsia |
6380 (14.0) |
425 (9.8) |
3971 (12.6) |
1216 (17.5) |
768 (26.0) |
<0.0001 |
| Missing |
65 (0.1) |
4 (0.1) |
44 (0.1) |
11 (0.2) |
6 (0.2) |
|
| Weight gain (kg) |
|
|
|
|
|
<0.0001 |
| < 7.0 |
12863 (28.1) |
767 (17.6) |
7851 (24.9) |
2651 (38.1) |
1594 (53.9) |
|
| 7.0-9.4 |
9254 (20.2) |
905 (20.8) |
6721 (21.3) |
1234 (17.7) |
384 (13.3) |
|
| 9.5-12.7 |
12270 (26.8) |
1387 (31.9) |
9046 (28.7) |
1447 (20.8) |
390 (13.2) |
|
| > 12.7 |
11437 (25.0) |
1289 (29.7) |
7937 (25.2) |
1629 (23.4) |
582 (19.7) |
|
| Delivery method |
|
|
|
|
|
<0.0001 |
| Vaginal |
43422 (94.8) |
4171 (95.9 |
30073 (95.3) |
6506 (93.5) |
2672 (90.3) |
|
| Cesarean |
2401 (5.2) |
177 (4.1) |
1481 (4.7) |
455 (6.5) |
288 (9.3) |
|
| Missing |
1 (0.0) |
0 (0.0) |
1 (0.0) |
0 (0.0) |
0 (0.0) |
|
| Birth weight |
|
|
|
|
|
<0.0001 |
| Low (<2500 grams) |
4645 (10.1) |
713 (16.4) |
3259 (10.3) |
478 (6.9) |
195 (6.6) |
|
| Normal (≥ 2500 grams) |
41151 (89.8) |
3633 (83.6) |
28282 (89.6) |
6477 (93.1) |
2759 (93.2) |
|
| Missing |
28 (0.1) |
2 (0.1) |
14 (0.0) |
6 (0.1) |
6 (0.2) |
|
| Gestational Age |
|
|
|
|
|
<0.0001 |
| Spontaneous PTB with PROM |
3526 (7.7) |
384 (8.8) |
2421 (7.7) |
508 (7.3) |
213 (7.2) |
|
| Spontaneous PTB no PROM |
2278 (5.0) |
279 (6.4) |
1595 (5.1) |
283 (4.1) |
121 (4.1) |
|
| Indicated PTB |
557 (1.2) |
48 (1.1) |
381 (1.2) |
80 (1.2) |
48 (1.6) |
|
| Full Term Birth | 39463 (86.1) | 3637 (83.7) | 27158 (86.1) | 6090 (87.5) | 2578 (87.1) |