| Characteristic | Mg+ n = 88, n (%) | Mg− n = 498, n (%) | p Value |
| Histological endometritis* | 43/63 (68.3) | 197/439 (44.9) | 0.0005 |
| Pelvic pain score† (mean SD) | 67.7 (SD 21.3) | 65.6 (SD 21.5) | 0.392 |
| Co-infection | |||
| N gonorrhoeae and/or C trachomatis | 43/65 (66.2) | 172/435 (39.5) | < 0.0001 |
| N gonorrhoeae alone | 26/59 (44.1) | 111/423 (26.2) | 0.0045 |
| C trachomatis alone | 23/74 (31.1) | 91/484 (18.8) | 0.0147 |
| M hominis | 4/37 (10.8) | 17/203 (8.4) | 0.6295 |
| U urealyticum | 1/37 (2.7) | 15/203 (7.4) | 0.2932 |
| BV | 51/80 (63.8) | 254/453 (56.1) | 0.2006 |
| Demographic | |||
| Age | |||
| < 25 years | 71/88 (80.7) | 319/498 (64.1) | |
| ⩾ 25 years | 17/88 (19.3) | 179/498 (35.9) | 0.0023 |
| Race/ethnicity | |||
| African American | 69/88 (78.4) | 358/498 (71.9) | |
| White/Hispanic/Other | 19/88 (21.6) | 140/498 (28.1) | 0.2047 |
| Marital status | |||
| Unmarried | 71/78 (91.0) | 411/466 (88.2) | |
| Married | 7/78 (9.0) | 55/466 (11.8) | 0.4669 |
| Education | |||
| < High school | 38/88 (43.2) | 189/497 (38.0) | |
| ⩾ High school | 50/88 (56.8) | 308/497 (62.0) | 0.3605 |
| Sexual history | |||
| History of STD‡ | 51/86 (59.3) | 288/485 (59.4) | 0.9890 |
| History of BV | 13/86 (15.1) | 117/482 (24.3) | 0.0626 |
| Sexually active | 78/88 (88.6) | 415/498 (83.3) | 0.2095 |
| Rare/occasional condom use§ | 60/78 (76.9) | 289/415 (69.6) | 0.1943 |
| Consistent condom use¶ | 7/78 (9.0) | 57/415 (13.7) | 0.2511 |
| ⩾ 2 sexual partners | 10/88 (11.4) | 46/498 (9.2) | 0.5316 |
| Behavioural | |||
| Vaginal douche, 2+ times in past month | 26/88 (29.6) | 88/498 (17.7) | 0.0095 |
| Drug use | 32/88 (36.4) | 125/495 (25.3) | 0.0304 |
| Current smoker | 49/88 (55.7) | 194/495 (39.2) | 0.0038 |
*⩾5 surface epithelium neutrophils per ×400 field absent of menstrual endometrium and/or ⩾2 stromal plasma cells per ×120 field; †mean composite pain score = (mean of current pelvic pain score, average pelvic pain score and worst pelvic pain score) × 10; ‡history of Neisseria gonorrhoeae, Chlamydia trachomatis or Trichonomas vaginalis; §condoms used 0 to 5 out of 10 sexual encounters; ¶condoms used in 10 out of 10 sexual encounters.
BV, bacterial vaginosis; STD, sexually transmitted disease.