Table 4 Quality assessment of studies included in the systematic review
From: Caesarean delivery and subsequent pregnancy interval: a systematic review and meta-analysis
Study | Selection bias | Exposure bias | Outcome assessment bias | Confounding factor bias* | Analytical bias | Attrition bias | Overall likelihood of bias |
|---|---|---|---|---|---|---|---|
Eijsink et al., 2008 [32] | Moderate | Low | Low | High (no adjustment for confounders reported, matched by maternal age and date of delivery) | Low | Minimal | High |
Collin et al., 2006 [10] | Low | Low | Low | Minimal (adjusted for age, parity, level of education, urban or rural residence and young age at first intercourse) | Minimal | Low | Low |
Smith et al., 2006 [18] | Minimal | Low | Low | Minimal (adjusted for marital status, deprivation, birth weight, infant sex, maternal age, maternal height and method of induction) | Minimal | Minimal | Low |
Murphy et al., 2002 [7] | Low | Low | Low | Minimal (adjusted for maternal and paternal age, co-habitation, oral contraceptive pill use, cigarette exposure, alcohol consumption, educational level, ethnicity, parity, change of partner, maternal BMI) | Minimal | Minimal | Low |
Zdeb et al., 1984 [33] | Low | Low | Low | Moderate (none reported). Matching by race, complications of pregnancy, maternal education and maternal age | Moderate | Low | High |
Tollånes et al., 2007 [16] | Minimal | Low | Low | Minimal (stratified by maternal age, level of education and infant survival). Sub-group analyses by low-risk group, pre-eclampsia and breech presentation | Low | Minimal | Low |
Tower et al., 2000 [16] | Low | Low | Low | Moderate (no adjustment for confounding). Matching by age and date of delivery | Moderate | Moderate | High |
Huttly et al., 1990 [34] | Low | Low | Low | Minimal (adjusted for income, age, education and parity) | Moderate | Moderate | Low |
Hemminki, 1987 [37] | Low | Low | Low | Moderate (no adjustment for confounders). Matching by year of birth, maternal age and infant sex | Moderate | Low | High |
LaSala et al., 1987 [35] | Moderate | Low | Minimal | Moderate (no adjustment for confounding reported). Matching by age and parity | Moderate | Moderate | High |
Hemminki et al., 1985 [36] | Low | Low | Minimal | Moderate (no adjustment reported). Matching by date of birth, mother’s age, race and marital status | Moderate | Minimal | High |