Placenta praevia after prior caesarean section: an exploratory case-control study.

Chiu, Tin Lok; Sadler, Lynn; Wise, Michelle R

OBJECTIVE To identify additional risk factors for placenta praevia in women with prior caesarean section. METHOD A retrospective case-control study of 53 cases and 157 controls was performed. Information was obtained from the National Women's database between 2004 and 2009. Cases were defined as women with diagnosed placenta praevia over 20 weeks' gestation and having had one or more prior caesarean sections. Risk factors assessed from the prior caesarean section were (i) type of suture used for hysterotomy closure; (ii) stage of labour; (iii) type of primary surgeon; and (iv) model of funding. Univariate and logistical regression analyses were performed. RESULTS Use of monofilament suture for hysterotomy closure in prior caesarean section significantly reduced the chance of having placenta praevia in the index pregnancy (adjusted odds ratio 0.26, 95% confidence interval 0.08-0.80), as did prior caesarean being performed in the first stage of labour (aOR 0.36, 95% CI 0.14-0.92). Type of primary surgeon (specialist vs trainee junior doctor), nor model of funding of prior caesarean section (public vs private), was associated with risk of placenta praevia (privately funded specialist aOR 4.75, 95% CI 0.89-25.23 and trainee junior doctor aOR 3.18, 95% CI 0.59-17.28, respectively). CONCLUSION A prior caesarean section performed in first stage, and monofilament suture for hysterotomy closure, reduced the chance of having placenta praevia in the index pregnancy.