Table 1. Descriptive statistics for participants' preterm birth and categorical attributes.
| Categorical variables | Count, no | Count, yes | Yes, % | |
|---|---|---|---|---|
| Preterm birth | 608 | 123 | 16.8 | |
| Upper gastrointestinal tract symptom | 487 | 244 | 33.4 | |
| GERD | 517 | 214 | 29.3 | |
| Helicobacter pylori | 663 | 68 | 9.3 | |
| Periodontitis | 679 | 52 | 7.1 | |
| Education, below high school graduation | 546 | 185 | 25.3 | |
| Income, public insurance/Medicaid only | 662 | 69 | 9.4 | |
| Region, rural | 721 | 10 | 1.4 | |
| Smoking | 724 | 7 | 1.0 | |
| Drinking | 713 | 18 | 2.5 | |
| Diabetes mellitus | ||||
| Type I | 728 | 3 | 0.4 | |
| Type II | 726 | 5 | 0.7 | |
| Gestational | 686 | 45 | 6.2 | |
| Hypertension | ||||
| Chronic | 722 | 9 | 1.2 | |
| Gestational | 720 | 11 | 1.5 | |
| Medication history | ||||
| Progesterone | 534 | 197 | 26.9 | |
| Calcium channel blocker | 655 | 76 | 10.4 | |
| Nitrate | 729 | 2 | 0.3 | |
| Tricyclic antidepressant | 727 | 4 | 0.5 | |
| Benzodiazepine | 712 | 19 | 2.6 | |
| Sleeping pills | 726 | 5 | 0.7 | |
| Parity, code 0000a | 276 | 455 | 62.2 | |
| Prior preterm birth | 686 | 45 | 6.2 | |
| Twin | 715 | 16 | 2.2 | |
| Myoma uteri | 699 | 32 | 4.4 | |
| Adenomyosis | 730 | 1 | 0.1 | |
| Preeclampsia | 709 | 22 | 3.0 | |
| In vitro fertilization | 717 | 14 | 1.9 | |
| Prior previa | 726 | 5 | 0.7 | |
| Prior cone | 723 | 8 | 1.1 | |
| Pelvic inflammatory disease history | 721 | 10 | 1.4 | |
| Infant sex, female | 382 | 349 | 47.7 | |
GERD = gastroesophageal reflux disease.
a0 Full-term birth, 0 preterm birth, 0 abortion, 0 children alive.