Increased risk of placenta accreta following primary elective caesarean delivery: a case-controlled study

by faithgibson on March 4, 2013

BJOG: An International Journal of Obstetrics and Gynaecology, 03/04/2013

CONCLUSION: Compared with primary emergency caesarean section, primary elective caesarean section significantly increased the risk of placenta accreta in a subsequent pregnancy in the presence of *placenta praevia (OR 3.00; 95% CI 1.47–6.12; P = 0.025).

*editor’s note: Obviously, follow-up studies on women with previas (all of whom had pre-labor Cesareans) give researchers a controlled cohort and a constant (rather than variable) set of conditions, which makes findings in a comparison study more reliable.  

The issue of increased abnormal placentation following a primary elective (pre-labor) Cesarean for previa (usually scheduled at 36-38 wks) may be related to the fact that at the time of the index surgery, the lower segment (non-fundal bottom third) of the uterus had not yet remodeled and thinned itself out in preparation for labor.

This would make the incision into the uterus much higher in the uterine musculature (instead of the very thinned out lower third seen in laboring women) . This may ncreases the likelihood of previa in subsequent pregnancies, which it itself is associated w/ increased accreta/percrata.

This mechanism would apply to any Cesarean performed before the lower segment was substantially remodeled by the biological processes of late pregnancy, a ripe cervix and enough active labor to produce the classically thinned out lower uterine segment.

Kamara. M  et al. –  To evaluate the risk of placenta praevia accreta following primary (first) elective or primary emergency caesarean section in a pregnancy complicated by placenta praevia.

The study  results suggest that women with a primary elective caesarean section without labour are more likely, compared with those undergoing primary emergency caesarean section with labour, to develop an accreta in a subsequent pregnancy with placenta praevia.


  • Retrospective matched case–control study, employing variable matching conducted at Tertiary referral centre between 1993 and 2008.
  • Sixty–five cases and 102 controls were used for the analysis from a total of 82667 births during the study period
  • Main outcome measures were placenta accreta in a pregnancy complicated by placenta praevia following a primary elective or emergency caesarean section, and morbidity associated with pregnancies complicated by placenta accreta.
  • Relevant data were abstracted from clinical records.
  • Matching of cases with controls was based on co–existing placenta praevia, number of previous caesarean sections, and age, with one or two controls per case.
  • Results are presented as odds ratios (ORs) with 95% confidence intervals (95% CIs).


  • Significantly more cases than controls had an elective caesarean section for their primary caesarean delivery (46.2 versus 18.6%; P < 0.001).
  • No differences between groups for previous pregnancy loss, uterine surgery, and vaginal delivery, before or after the primary caesarean section.
  • Compared with primary emergency caesarean section, primary elective caesarean section significantly increased the risk of placenta accreta in a subsequent pregnancy in the presence of placenta praevia (OR 3.00; 95% CI 1.47–6.12; P = 0.025).

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