Table 1.
Characteristics of the study subjects according to the method of pregnancy
| Characteristics | Spontaneous conception | Non-ART treatment | CT | BT | Spontaneous vs Non-ART treatment vs CT and BT |
|---|---|---|---|---|---|
| Mother (Pregnancies) (n) | 92,022 | 3546 | 728 | 2020 | |
| Age (year) | 30.4 ± 5.0 | 32.7 ± 4.2 | 35.6 ± 4.0 | 35.6 ± 3.9 | <.0001 |
| BMI (kg/m2) | 21.2 ± 3.3 | 21.4 ± 3.6 | 21.3 ± 3.0 | 21.3 ± 3.1 | <.0001 |
| Metabolic equivalent/min | 414.1 ± 732.9 | 334.8 ± 604.6 | 256.0 ± 488.1 | 258.6 ± 462.5 | <.0001 |
| Calorie intake | 385.4 ± 729.3 | 318.0 ± 597.4 | 235.0 ± 453.0 | 249.5 ± 551.8 | <.0001 |
| Low education (%) | 37.3 | 22.4 | 21.9 | 22.8 | <.0001 |
| Smoking habit (%) | 18.9 | 8.5 | 4.4 | 4.8 | <.0001 |
| Alcohol consumption habit (%) | 65.6 | 63.2 | 60.6 | 62.4 | <.0001 |
| Physical component summary (SF-8 score) | 45.3 ± 5.3 | 44.1 ± 7.6 | 43.7 ± 7.9 | 43.8 ± 8.2 | <.0001 |
| Mental component summary (SF-8 score) | 46.1 ± 7.3 | 46.9 ± 7.1 | 47.6 ± 7.2 | 47.0 ± 7.0 | <.0001 |
| Assessing depression (K6 score) | 3.7 ± 3.9 | 3.2 ± 3.4 | 2.8 ± 3.0 | 3.0 ± 3.4 | <.0001 |
| Hyperlipidemia (%) | 0.5 | 1.3 | 0.5 | 0.7 | <.0001 |
| Diabetes (%) | 0.2 | 0.4 | 0.5 | 0.5 | <.0001 |
| Hyperthyroidism (%) | 1.0 | 1.3 | 1.4 | 1.8 | 0.001 |
| Hypothyroidism (%) | 0.9 | 2.1 | 3.4 | 3.9 | <.0001 |
| Family | |||||
| Low income (%) | 41.5 | 26.8 | 16.7 | 20.2 | <.0001 |
| Father (n) | 47,208 | 1929 | 410 | 1082 | |
| Age (year) | 32.4 ± 5.8 | 34.4 ± 5.2 | 37.2 ± 5.4 | 37.6 ± 5.5 | <.0001 |
| BMI (kg/m2) | 23.4 ± 3.5 | 23.5 ± 3.4 | 23.9 ± 3.2 | 23.8 ± 3.3 | <.0001 |
| Low education (%) | 45.1 | 31.3 | 30.3 | 32.3 | <.0001 |
| Smoking habit (%) | 51.2 | 38.7 | 33.8 | 33.6 | <.0001 |
| Alcohol consumption habit (%) | 78.8 | 78.0 | 78.1 | 80.1 | NS |
| Physical component summary (SF-8 score) | 51.0 ± 5.3 | 51.1 ± 5.3 | 51.2 ± 4.7 | 50.9 ± 5.3 | NS |
| Mental component summary (SF-8 score) | 49.8 ± 6.1 | 49.9 ± 6.2 | 50.0 ± 6.2 | 50.1 ± 5.9 | NS |
| Assessing depression (K6 score) | 2.6 ± 3.5 | 2.5 ± 3.4 | 2.3 ± 3.2 | 2.5 ± 3.5 | NS |
| Infants (n) | 92,545 | 3696 | 751 | 2102 | |
| Male (%) (95% CI) | 51.3 (49.2–53.4) | 50.7(48.6–52.8) | 48.9 (45.3–52.5) | 53.4 (51.3–55.5) | NS |
| Sex ratio | 1.05 | 1.03 | 0.96 | 1.15 | |
| Pregnancies (n) | 92,022 | 3546 | 728 | 2020 | |
| Single (%) | 99.4 | 95.8 | 96.8 | 95.9 | <.0001 |
| Multiple (%) | 0.6 | 4.2 | 3.2 | 4.1 | |
| [Monozygotic twinning (%)] (95% CI) | 0.27 (0.23–0.30) | 0.11 (0–0.22) | 0.27 (0–0.65) | 0.99 (0.56–1.42) | <.0001 |
Data are shown as mean ± SD (The percentages are drawn from available data and the total number varies for each category because of missing values and refer to the Additional file 2.). Smoking and alcohol consumption habits at pregnancy recognition, SF-8 score of 50 or less. Low education: defined by the highest academic background and categorized as graduation from high school or less, Low income: defined by the annual revenue of the household and categorized as an annual income of 4,000,000 Japanese yen or less. The P values are listed simply to give an indication of the magnitude of the inter-group differences. It is not intended that all those P values should have the customary probabilistic interpretation
BMI (body mass index), CT (early cleavage-stage embryo transfer), BT (blastocyst transfer), NS (not statistically significant)