Table 1

Characteristics of included studies

AuthorYearStateStudy designNo of casesNo of hospital unitsYear of data collectionPopulationSamplingType of CS analysed
Stafford20 1990CaliforniaCross-sectional461 066Not reported1986Primipara and multipara; any riskConsecutiveAny
Haas et al 15 A1993MassachusettsCross-sectional57 257Not reported1984Primipara and multipara; any riskConsecutiveAny
Haas et al 15 B1993MassachusettsCross-sectional64 346Not reported1987Primipara and multipara; any riskConsecutiveAny
Braveman et al 209 1995CaliforniaRetrospective cohort213 761Unclear1991Primipara; no previous CS; any riskConsecutiveAny
Burns et al 21 1995ArizonaCross-sectional33 233361989Primipara and multipara; any riskConsecutiveAny
Onion et al 210 A1999MaineCross-sectional41 177Not reported1990–1992Primipara; no previous CS; any riskConsecutiveAny
Onion et al 210 B1999New HampshireCross-sectional41 401Not reported1990–1992Primipara; no previous CS; any riskConsecutiveAny
Onion et al 210 C1999VermontCross-sectional19 077Not reported1990–1992Primipara; no previous CS; any riskConsecutiveAny
Aron et al 211 2000OhioRetrospective cohort25 697211993–1995Primipara; no previous CS; any riskConsecutiveAny
Grant22 A2005All statesCross-sectional9017Not reported1988Primipara and multipara; any riskRandomAny
Grant22 B2005FloridaCross-sectional147 821Not reported1992Primipara and multipara; any riskConsecutiveAny
Coonrod et al 62 2008ArizonaCross-sectional28 863402005Primipara; low riskConsecutiveAny
Huesch212 2011New JerseyCross-sectional182 108Not reported2004–2007Primipara and multipara; no previous CS; low riskConsecutivePlanned
Kozhimannil et al 103 2014All statesCross-sectional6 717 486Over 10002002–2009Primipara and multipara; any riskRandomAny
Huesch et al 213 2014CaliforniaCross-sectional408 3552542010Primipara and multipara; no previous CS; any riskConsecutivePlanned
Sebastião et al 214 2016FloridaRetrospective cohort412 1921222004–2011Primipara; no previous CS; low riskConsecutiveEmergency
  • CS, caesarean section.