Table 2.
Characteristics of the included primary studies
| Number (%) of studies | |
|---|---|
| Year of publication | |
| 1990-1994 | 8 (22) |
| 1995-1999 | 9 (25) |
| 2000-2004 | 15 (42) |
| 2005-2008 (part year) | 4 (11) |
| Country | |
| USA | 26 (72) |
| Australia | 4 (11) |
| U.K. | 4 (11) |
| Canada | 1 (3) |
| Greece | 1 (3) |
| Study design | |
| RCT-individually randomized | 7 (19) |
| RCT-cluster randomized | 2 (6) |
| Retrospective cohort study | 12 (33) |
| Prospective cohort study | 6 (17) |
| Cohort study (unspecified) | 2 (6) |
| Mixed retrospective/prospective cohort study | 1 (3) |
| Before and after study | 6 (17) |
| Outcomes reported* | |
| PTB/preterm labour | 32 (89) |
| Infant mortality | 5 (14) |
| Neonatal mortality | 6 (17) |
| Congenital anomalies | 6 (17) |
* Not mutually exclusive