Table 1.
Maternal characteristics and obstetric factors among women with short interpregnancy interval and a reference interpregnancy interval (n = 144,733)
| Maternal characteristics | Interpregnancy interval subgroups | ||||||
|---|---|---|---|---|---|---|---|
| < 6 months n = 16,903 | 6–11 months n = 40,985 | 12–17 months n = 48,710 | 18–23 months (Ref) n = 38,135 | ||||
| n (%) | p | n (%) | p | n (%) | p | n (%) | |
| Maternal age | |||||||
| < 18 years | 1286 (7.6) | < 0.001 | 1956 (4.8) | < 0.001 | 1970 (4.0) | 0.265 | 1600 (4.2) |
| 18–34 years | 14,586 (86.3) | 0.400 | 34,834 (85.0) | < 0.001 | 41,578 (85.4) | < 0.001 | 33,009 (86.6) |
| > 34 years | 1031 (6.1) | < 0.01 | 4194 (10.2) | < 0.001 | 5161 (10.6) | < 0.001 | 3525 (9.2) |
| Maternal education | |||||||
| < 12 years | 3537 (20.9) | < 0.001 | 5207 (12.7) | < 0.001 | 4795 (9.8) | 0.598 | 3795 (10.0) |
| 12 years | 5489 (32.5) | < 0.001 | 9797 (23.9) | < 0.001 | 9487 (19.5) | 0.002 | 7743 (20.3) |
| > 12 years | 7371 (43.6) | < 0.001 | 24,701 (60.3) | < 0.001 | 32,858 (67.5) | 0.024 | 25,447 (66.7) |
| Medicaid payment for delivery | 8723 (51.6) | < 0.001 | 13,858 (33.8) | < 0.001 | 12,916 (26.5) | 0.910 | 10,125 (26.6) |
| Enrolled in WIC | 9860 (58.3) | < 0.001 | 16,050 (39.2) | < 0.001 | 15,168 (31.1) | 0.305 | 11,999 (31.5) |
| Race and ethnicity | |||||||
| White, not hispanic | 4258 (25.2) | < 0.001 | 15,211 (37.1) | < 0.001 | 20,736 (42.6) | 0.134 | 16,041 (42.1) |
| Hispanic | 8062 (47.7) | < 0.001 | 14,236 (34.7) | < 0.001 | 14,459 (29.7) | 0.051 | 11,553 (30.3) |
| Black | 1197 (7.1) | < 0.001 | 2119 (5.2) | < 0.001 | 1928 (4.0) | 0.278 | 1565 (4.1) |
| Asian | 1973 (11.7) | < 0.001 | 6355 (15.5) | 0.0001 | 8134 (16.7) | 0.477 | 6299 (16.5) |
| Other | 1413 (8.4) | < 0.001 | 3064 (7.5) | 0.014 | 3453 (7.1) | 0.693 | 2677 (7.0) |
| Body mass index | |||||||
| Underweight (< 18.5 kg/m2) | 874 (5.2) | 0.006 | 2216 (5.4) | 0.033 | 2677 (5.5) | 0.098 | 2195 (5.8) |
| Normal (18.5–24.9 kg/m2) | 7852 (46.5) | < 0.001 | 22,214 (54.2) | < 0.001 | 27,950 (57.4) | 0.883 | 21,863 (57.3) |
| Overweight (25.0–29.9 kg/m2) | 3746 (22.2) | < 0.001 | 8340 (20.4) | < 0.001 | 9478 (19.5) | 0.378 | 7331 (19.2) |
| Obese (≥ 30 kg/m2) | 3325 (19.7) | < 0.001 | 5798 (14.2) | < 0.001 | 5880 (12.1) | 0.483 | 4544 (11.9) |
| Gestational Diabetes | 1062 (6.3) | 0.093 | 2549 (6.2) | 0.072 | 2775 (5.7) | 0.176 | 2255 (5.9) |
| Gestational Hypertension | 739 (4.4) | 0.573 | 1777 (4.3) | 0.631 | 1966 (4.0) | 0.091 | 1627 (4.3) |
| Preeclampsia | 912 (5.4) | < 0.001 | 1826 (4.5) | 0.148 | 2023 (4.2) | 0.501 | 1619 (4.3) |
| Smoking during Pregnancy | 914 (5.6) | < 0.001 | 1591 (3.9) | < 0.001 | 1511 (3.10 | 0.131 | 1252 (3.3) |
| Drug or Alcohol Abuse | 426 (2.5) | < 0.001 | 701 (1.7) | < 0.001 | 602 (1.2) | 0.080 | 422 (1.1) |
| Mental Health Diagnosis | 572 (3.4) | < 0.001 | 1097 (2.7) | < 0.001 | 1069 (2.2) | 0.638 | 855 (2.2) |
| Previous Preterm Birth | 1462 (8.7) | < 0.001 | 2776 (6.8) | 0.0006 | 2943 (6.0) | 0.415 | 2355 (6.2) |
WIC women, infants, and children program