Table 1.
Characteristics of study participants
| Characteristics |
Unexposed to epidural analgesia during labor
(n = 41,234) |
Exposed to epidural analgesia during labor
(n = 938) |
||
| Maternal characteristics | ||||
| Age at delivery, years | ||||
| Mean (SD) | 31.3 | (4.8) | 32.5 | (4.7) |
| <20 | 420 | (1.0) | 5 | (0.5) |
| 20–29 | 14,705 | (35.7) | 244 | (26.0) |
| 30–39 | 24,453 | (59.3) | 623 | (66.4) |
| ≥40 | 1,655 | (4.0) | 66 | (7.0) |
| Parity | ||||
| Primipara | 17,419 | (43.3) | 495 | (53.4) |
| Multipara | 22,830 | (56.7) | 432 | (46.6) |
| Delivery mode | ||||
| Spontaneous | 29,410 | (71.3) | 239 | (25.5) |
| Induced | 8,809 | (21.4) | 497 | (53.0) |
| Vacuum or forceps | 3,015 | (7.3) | 202 | (21.5) |
| Duration of labor, hours | ||||
| Mean (SD) | 8.7 | (7.3) | 10.9 | (9.6) |
| <4.0 | 10,079 | (25.2) | 158 | (17.3) |
| 4.0–7.9 | 15,649 | (39.2) | 437 | (47.8) |
| ≥8.0 | 14,240 | (35.6) | 319 | (34.9) |
| Comorbidity | ||||
| Diabetes | 348 | (0.8) | 6 | (0.6) |
| Hypertension | 292 | (0.7) | 9 | (1.0) |
| BMI before pregnancy | ||||
| Mean (SD) | 20.9 | (2.9) | 20.8 | (2.7) |
| <18.5 | 6,992 | (17.0) | 177 | (18.9) |
| 18.5–24.9 | 30,894 | (75.0) | 697 | (74.4) |
| ≥25 | 3,326 | (8.1) | 63 | (6.7) |
| Occupation in the first trimester | ||||
| Yes | 26,660 | (66.3) | 581 | (64.8) |
| No | 13,526 | (33.7) | 316 | (35.2) |
| Smoking status | ||||
| Never-smoked | 25,701 | (62.3) | 545 | (58.1) |
| Ex-smoker (quit before pregnancy) | 9,524 | (23.1) | 248 | (26.4) |
| Ex-smoker (quit during early pregnancy) | 4,453 | (10.8) | 84 | (9.0) |
| Current smoker | 1,223 | (3.0) | 31 | (3.3) |
| Alcohol consumption | ||||
| Never drank | 14,569 | (35.5) | 305 | (33.6) |
| Ex-drinker | 22,317 | (54.5) | 521 | (57.3) |
| Current drinker | 4,099 | (10.0) | 83 | (9.1) |
| Education, years | ||||
| <13 | 13,257 | (32.3) | 247 | (26.4) |
| 13–15 | 17,688 | (43.1) | 394 | (42.1) |
| ≥16 | 10,057 | (24.5) | 295 | (31.5) |
| Annual household income | ||||
| <4,000,000 JPY | 14,777 | (38.2) | 246 | (28.0) |
| 4,00,000–7,999,999 JPY | 19,547 | (50.5) | 468 | (53.2) |
| ≥8,000,000 JPY | 4,358 | (11.3) | 166 | (18.9) |
| Marital status at 6 months after childbirth | ||||
| Married (including common-law marriage) | 40,441 | (98.1) | 924 | (98.5) |
| Divorced | 209 | (0.5) | 6 | (0.6) |
| Widowed | 14 | (0.0) | 1 | (0.1) |
| Others | 308 | (0.7) | 3 | (0.3) |
|
| ||||
| Child’s characteristics | ||||
| Sex | ||||
| Male | 21,023 | (51.0) | 461 | (49.1) |
| Female | 20,211 | (49.0) | 477 | (50.9) |
| Birth weight | ||||
| Mean (SD) | 3080.7 | (356.4) | 3048.2 | (351.6) |
| <2500 | 1,820 | (4.4) | 55 | (5.9) |
| 2500–3999 | 39,051 | (94.7) | 879 | (93.8) |
| ≥4000 | 357 | (0.9) | 3 | (0.3) |
| Apgar score at 5 min | ||||
| <7 | 117 | (0.3) | 0 | (0.0) |
| ≥7 | 39,742 | (99.7) | 920 | (100.0) |
| Feeding methods in infancy | ||||
| Breast | 20,335 | (49.3) | 347 | (37.0) |
| Bottle | 3,260 | (7.9) | 112 | (11.9) |
| Mixed | 17,639 | (42.8) | 479 | (51.1) |
| Nursery attendance at 6 months old | ||||
| Yes | 2,350 | (5.7) | 54 | (5.8) |
| No | 38,831 | (94.3) | 883 | (94.2) |
| Nursery attendance at 12 months old | ||||
| Yes | 9,983 | (24.3) | 219 | (23.4) |
| No | 31,129 | (75.7) | 716 | (76.6) |
| Screen time at 12 months old | ||||
| No viewing | 4,250 | (10.4) | 107 | (11.5) |
| <1 | 13,926 | (34.1) | 302 | (32.5) |
| 1–<2 | 12,186 | (29.8) | 285 | (30.6) |
| 2–<4 | 7,950 | (19.4) | 171 | (18.4) |
| ≥4 | 2,565 | (6.3) | 65 | (7.0) |
| Sibling cohabitations | ||||
| No | 19,451 | (47.3) | 511 | (56.0) |
| Yes | 21,671 | (52.7) | 402 | (44.0) |
Data represent mean (SD) or n (%).
Abbreviations: SD, standard deviation; BMI, body mass index; JPY, Japanese yen.