Data has indicated increased spontaneous preterm birth (PTB) risk in patients with a previous second-stage cesarean delivery (CD), but the risk of bias is high, according to a recent review published in the American Journal of Obstetrics & Gynecology.
Takeaways
- Second-stage cesarean delivery (CD) may increase the risk of subsequent spontaneous preterm birth (sPTB) compared to operative vaginal delivery (OVD), indicating a potential association between delivery mode and preterm birth risk.
- The review suggests a 2-fold greater odds ratio for sPTB after second-stage CD versus OVD, highlighting the significance of mode of delivery in predicting preterm birth outcomes.
- Despite the observed association, the review emphasizes the high risk of bias in existing studies, underlining the need for further research to establish a clearer understanding of the relationship between second-stage CD and preterm birth risk.
- Alternatives to second-stage CD, such as spontaneous vaginal delivery and operative vaginal delivery, may potentially reduce the risk of preterm birth, suggesting the importance of considering delivery mode in obstetric decision-making.
- The findings underscore the urgency of identifying modifiable risk factors for preterm birth to mitigate infant morbidity and mortality, emphasizing the critical role of research in informing clinical practice and improving maternal and neonatal outcomes.
Approximately 10% of deliveries are PTB, which is a leading cause of infant death. Risk factors include prior PTB, maternal infections, smoking, short cervical length, and maternal hypertensive disorders of pregnancy. However, 70% of PTBs have an unknown cause, making it vital to determine modifiable risk factors to reduce infant morbidity and mortality.
Second-stage CD has been indicated as a potential risk factor for subsequent PTB (sPTB), but the biological mechanisms of this association remain speculative. Alternatives to second-stage CD include spontaneous vaginal delivery (SVD) and operative vaginal delivery (OVD), which may reduce PTB risk.
Investigators conducted a systematic review to evaluate the association between mode of delivery in the second stage of labor and sPTB, primarily comparing CD with OVD. Databases evaluated for literature include Embase, EmCare, MEDLINE, the Cochrane Library, CINAHL, Scopus, and the Web of Science.
Original retrospective cohort study designs from database inception to November 28, 2022, then to April 1, 2023, were eligible for inclusion. Additional eligibility criteria included participants having second-stage CD or OVD and reported PTB data in the subsequent pregnancy.
Exclusion criteria included missing full text, only providing information about iatrogenic or medically indicated PTBs, and being a commentary, abstract, editorial, review, or case report. Two independent reviewers screened titles and abstracts, with a third consulted to resolve disagreements. These reviewers also performed data extraction.
Cochrane’s 2022 Risk of Bias in Non-randomized Studies of Exposure tool was utilized to determine the risk of bias. There are 7 domains evaluated in the tool, including cofounding, measurement of exposure, selection of participants, postexposure interventions, missing data, measurement of outcome, and selection of reported result.
There were 18 studies including 605,138 patients included in the final analysis. All studies were retrospective cohort studies and published between 2004 and 2023. Patient information was collected using questionnaires or interviews alongside medical record data in 2 studies.
Subsequent birth outcomes after CD were reported in 16 studies vs after OVD in 11 studies. First-stage CD, SVD, elective or prelabor CD, all intrapartum CD, and all CDs were reported as comparators.
Spontaneous PTB was reported in 6.8% of pregnancies after second-stage CD and 2.6% after OVD. For overall PTB, these rates were 7.1% and 2.6%, respectively. For comparators, PTB was reported in 3.9% of first-stage CD, 2.1% of elective or prelabor CD, and 3.1% of SVD.
In studies directly comparing the odds of subsequent spontaneous PTB, a 2-fold greater odds ratio (OR) was observed for second-stage CD vs OVD. The rates of spontaneous PTB were 5.2% and 3%, respectively.
These comparisons were made across 7 studies, 2 of which had a medium risk of bias and 5 had a high risk of bias. For the medium risk studies, an OR of 2.47 was reported. When evaluating all PTBs, the OR was 2.01, and extreme PTB had an OR of 7.25.
When comparing sPTB rates after second-stage CD vs first-stage CD, rates of 6.97% and 3.64%, respectively, were reported. This indicated an OR of 2. Of the studies evaluating this association 3 had a medium risk of bias and 6 a high risk of bias.
When comparing sPTB rates after an OVD vs SVD, rates of 2.6% and 2.9%, respectively, were reported, with a pooled OR of 0.86. This comparison was made across 7 studies, 3 with a medium risk of bias and 4 with a high risk of bias. Overall, 13 studies had a high risk of bias and 5 had a medium risk of bias.
These results indicated an association between second-stage CD and increased PTB risk. However, because of the high risk of bias, investigators recommended further research directly comparing second-stage CD and OVD.
Reference
Kirubarajan A, Thangavelu N, Rottenstreich M, Muraca GM. Operative delivery in the second stage of labor and preterm birth in a subsequent pregnancy: a systematic review and meta-analysis. American Journal of Obstetrics & Gynecology. 2024;230(3):295-307. doi:10.1016/j.ajog.2023.08.033
