Influence of Caesarean section–pregnancy interval on uterine rupture risk and IVF pregnancy rates: systematic review and mathematical modelling

Research question What is the influence of the Caesarean section–pregnancy interval (CSPI) on the risk of uterine rupture, and what are the repercussions on IVF pregnancy rates of prolonging it? Study design Systematic searches were performed using PubMed MEDLINE to identify studies published up until July 2017 for articles with the following keywords: ‘interdelivery interval’ and ‘uterine rupture’; ‘interpregnancy interval’ and ‘uterine rupture’; ‘interpregnancy interval’ and ‘cesarean section’; and ‘uterine rupture’ and ‘cesarean section’. The search identified 1609 articles, of which six were included (involving 56,419 women). Four reported significantly higher uterine rupture rates in cases of a short CSPI. Results From the analysis, the uterine rupture rate can be modelled by a formula corresponding to a hyperbolic curve. There is no clear cut-off in uterine rupture in relation to CSPI. The curve showed a sharp decrease in uterine rupture until the 10th month of CSPI (uterine rupture rate 0.7%), then a moderate and steady decrease until the 40th month (uterine rupture rate 0.4%) and afterwards a very mild decrease. From the data it is possible to calculate, according to the age of the woman, the expected reduction in IVF rates and uterine rupture as CSPI increases. Conclusion The risk of uterine rupture in relation to CSPI can be represented by means of a hyperbolic curve. After a 10-month CSPI, the expected uterine rupture rate is close to 0.7%. The impact of prolonging or reducing this interval on IVF pregnancy rates can be easily obtained from the table included in the article. This should be helpful in the decision-making process for both patients and physicians.