Table 3. Sociodemographic and clinical characteristics of participants according to the weeks of resuming postpartum menstruation.
| < 72 weeks n = 701 |
≥ 72 weeks n = 61 |
P | |
| Age at delivery | 31 (28, 35) | 34 (31, 37.5) | < 0.01** |
| Age at first childbirth | 28 (25, 32) | 30 (27.5, 32) | 0.03* |
| Parity | 0.01* | ||
| Primiparous | 43.7 (303) | 27.1 (16) | |
| Multiparous | 56.3 (391) | 72.9 (43) | |
| BMI before pregnancy (kg/m2) | 20.6 (18.9, 22.3) | 19.9 (18.6, 21.5) | 0.09 |
| Highest level of maternal education | |||
| Junior high school / High school | 28.8 (201) | 19.7 (12) | 0.13 |
| Vocational school / Junior college / University / Graduate School | 71.2 (498) | 80.3 (49) | |
| Highest level of partner’s education | 0.35 | ||
| Junior high school / High school | 41.2 (287) | 35.0 (21) | |
| Vocational school / Junior college / University / Graduate School | 58.8 (410) | 65.0 (39) | |
| Annual household income during pregnancy | 0.99 | ||
| < 4,000,000 JPY | 37.8 (253) | 36.8 (21) | |
| 4,000,000~5,990,000 JPY | 34.8 (233) | 35.1 (20) | |
| ≥ 6,000,000 JPY | 27.4 (183) | 28.1 (16) | |
| Age at first menstrual period (year) | 0.26 | ||
| < 15 | 93.3 (637) | 88.7 (47) | |
| ≥ 15 | 6.7 (46) | 11.3 (6) | |
| Infertility treatment | 0.03* | ||
| No | 96.4 (675) | 90.2 (55) | |
| Yes | 3.6 (25) | 9.8 (6) | |
| History of taking oral contraceptives | < 0.01** | ||
| No | 90.4 (628) | 76.3 (45) | |
| Yes | 9.6 (67) | 23.7 (14) | |
| Past history Irregular menstruation |
< 0.01** | ||
| No | 89.1 (620) | 72.9 (43) | |
| Yes | 10.9 (76) | 27.1 (16) | |
| Pregnancy complication Diabetes |
0.10 | ||
| No | 99.3 (696) | 96.7 (59) | |
| Yes | 0.7 (5) | 3.3 (2) | |
| Obstetric complication Gestational diabetes |
< 0.01** | ||
| No | 99.4 (697) | 91.8(56) | |
| Yes | 0.6 (4) | 8.2 (5) | |
| Mode of delivery | 0.98 | ||
| Vaginal delivery | 83.7 (587) | 83.6 (51) | |
| Cesarean section | 16.3 (114) | 16.4 (10) | |
| Gestational age (weeks) | 39 (38, 40) | 39 (38, 39.5) | 0.23 |
| K6 score (First trimester) | 2.0 (0.0, 6.0) | 4.0 (1.0, 7.0) | 0.02* |
| K6 score (Second/third trimester) | 2.0 (0.0, 4.0) | 3.0 (1.0, 5.0) | 0.14 |
| K6 score (1 year after delivery) | 1.0 (0.0, 4.0) | 2.0 (0.5, 5.0) | 0.06 |
| Edinburgh Postnatal Depression Scale score (1 month after delivery) | 5.0 (3.0, 7.0) | 4.0 (2.0, 8.0) | 0.62 |
| Edinburgh Postnatal Depression Scale score (6 months after delivery) | 4.0 (2.0, 6.0) | 4.0 (2.0, 6.0) | 0.66 |
| The Japanese version of the Mother-to-infant Bonding Scale (at 1 year postpartum) | 1.0 (0.0, 2.0) | 1.0 (0.0, 3.0) | 0.76 |
| Current employment status (1 year after delivery) |
0.60 | ||
| Employed | 15.6 (108) | 13.1 (8) | |
| Unemployed | 84.4 (583) | 86.9 (53) |
Data are median (interquartile range) or % (n). Pats history other than irregular menstruation, pregnancy complications other than diabetes, and obstetric complications other than gestational diabetes are listed in Supplemental Table 1. Data were missing on age at first childbirth (n = 56), parity (n = 9), highest level of maternal education (n = 2), highest level of partner's education (n = 5), annual household income during pregnancy (n = 36), age at first menstrual period (n = 26), infertility treatment (n = 1), history of taking oral contraceptives (n = 8), past history irregular menstruation (n = 7), K6 score (First trimester) (n = 13), K6 score (Second/third trimester) (n = 7), K6 score (1 year after delivery) (n = 11), Edinburgh Postnatal Depression Scale score (1 month after delivery) (n = 5), Edinburgh Postnatal Depression Scale score (6 months after delivery) (n = 14), The Japanese version of the Mother-to-infant Bonding Scale (at 1 year postpartum) (n = 15), Current employment status (n = 10). Distribution normality was confirmed using the Shapiro–Wilk test. Calculated using the Mann–Whitney U test or Chi-squared test (2 × 2 groups). *P < 0.05, **P < 0.01.