Table II.
Characteristics of included studies
| Year | First Author | Total population | Total w/ bleeding (%)* | Study design | Definition of Bleeding |
|---|---|---|---|---|---|
| 1980 | Funderburk[16] | 25,377 | 259 (1.0%) | Population sample. Record review, not otherwise specified, presumed retrospective | At least one episode of spotting |
| 1983 | Berkowitz[6] | 16,305 | 2,385 (14.6%) | Population sample. Retrospective review of post-partum questionnaire | Greater or less then menses |
| 1984 | Batzofin[17] | 7,229 | 523 (7.2%) | Population sample. Record review, not otherwise specified, presumed retrospective | Deemed significant by provider |
| 1985 | Hertz[5] | 375 | 93 | Convenience sample Presumed prospective, though unclear | “Threatened abortion” defined as vaginal bleeding with or without cramps |
| 1989 | Strobino[8] | 3,346 | 744 (22.2%) | Population sample Prospective after second trimester interview | At least “spotting or slight” for “Light” and “characterized as moderate or heavy” for “Heavy” |
| 1992 | Sipila[19] | 8,718 | 807 (9.3%) | Population sample Questionnaire at 24 wks then prospective collection of delivery data | “Light” subgroup did not require hospital care “Heavy” subgroup had been admitted. |
| 1991 | Williams[18] | 11,444 | 1,174 (12%) | Population sample Retrospective review of post-partum questionnaire | Present or absent only |
| 1993 | Verma[9] | 113 | 63 | Convenience sample Unclear if retrospective or prospective | Clinically diagnosed with “threatened abortion” |
| 1995 | Tongsong[26] | 520 | 255 | Convenience sample Prospective with subjects enrolled at the time of bleeding | Vaginal bleeding sufficient for an ultrasound to have been ordered |
| 1996 | Das[7] | 110 | 55 | Convenience sample Presumed prospective | Vaginal bleeding sufficient for ultrasound examination |
| 1998 | Karim[27] | 268 | 95 | Convenience sample retrospective medial record review | Present or absent only |
| 1998 | Signore[28] | 334 | 167 | Convenience sample retrospective chart review | Vaginal bleeding sufficient for ultrasound examination |
| 1999 | French[20] | 1,169 | 190 (15.8%) | Population sample Secondary analysis of prospective trial | Not defined |
| 2000 | Arafa[21] | 1,503 | 159 (10.6%) | Population sample Interviewed postpartum | “Light”: one episode of spotting; “Heavy”: > 1 teaspoon |
| 2001 | Yang[15] | 8671 | 308 (4.3%) | Population sample Retrospective review of questionnaire | Sufficient for Bed rest** |
| 2003 | Harville[23] | 136 | 14 (8.8%) | Population sample Prospective patient log | Requires a pad for at at least a day |
| 2004 | Mulik[13] | 6,903 | 458 (6.6%) | Population sample Retospective analysis of database | Not defined |
| 2004 | Yang[14] | 2,802 | 683 (24.3%) | Population sample Questionnaire at 24–29 Weeks, prospective | Any bleeding or spotting |
| 2004 | Weiss[24] | 16,506 | 2,346 (14.2%) | Population sample Secondary analysis of prospective study. 1st trimester questionnaire | “Light”: Spotting only “Heavy”: Similar to menses |
| 2006 | Wijesiriwardana[12] | 39,260 | 7,627 (19.4%) | Population sample. “Retrospective cohort” | Sufficient for subjects to seek hospital assessment prior to 12 weeks |
| 2006 | Johns[29] | 214 | 214 | Convenience sample Prospective | Vaginal bleeding sufficient for referral, “spotting” was excluded |
| 2007 | Hossain[25] | 2,678 | 622 (26.2%) | Population sample. Interview prior to 20 wks, then data collected prospectively | Present or absent only |
| 2008 | Davari-Tanha[30] | 600 | 150 | Convenience sample Prospective | Not defined |
*
The percent incidence of vaginal bleeding is only provided for studies that utilized a population sample.
**
”1st half of pregnancy” and “more severe” subgroups were selected from many different available subgroups for meta-analysis as this was most similar to other included studies