Timing of Repeat Cesarean Section at 40 Weeks
For women with a previous cesarean section, scheduling repeat cesarean delivery at 39-40 weeks gestation minimizes neonatal respiratory complications while avoiding the risks of spontaneous labor, particularly when trial of labor after cesarean (TOLAC) is not planned or appropriate. 1
Primary Rationale for 40-Week Timing
The American College of Obstetricians and Gynecologists specifically recommends scheduling repeat cesarean at 39-40 weeks gestation to achieve two critical goals 1:
- Minimize neonatal respiratory complications that occur more frequently with earlier delivery 1
- Avoid spontaneous labor onset, which carries a 0.35% uterine rupture risk compared to 0.22% overall 1
Except in particular clinical situations, elective repeat cesarean must not be performed before 39 weeks to reduce the risk of transient respiratory distress 2
Special Consideration: Women with Cardiac Disease
For all women with cardiac disease (regardless of cesarean history), induction of labor should be considered at 40 weeks gestation 3. This recommendation applies broadly to cardiac patients and provides additional rationale for the 40-week timing in women who also have previous cesarean deliveries.
Risk Profile Supporting Scheduled Cesarean
For patients with one previous cesarean, the comparative risks favor scheduled cesarean in certain contexts 1:
- Overall maternal morbidity: 2.23% with scheduled cesarean vs. 0.9% with planned vaginal birth (though not statistically significant for all comparisons) 1
- Perinatal mortality is higher with trial of labor compared to scheduled repeat cesarean 1, 3
- Maternal mortality is actually lower with successful VBAC compared to repeat cesarean, but this requires successful vaginal delivery 1
Factors That Increase Risk Beyond 40 Weeks
Research demonstrates that gestational age ≥40 weeks is a significant risk factor for failed TOLAC (odds ratio: 5.47,95% CI: 2.55-11.70) 4. This finding supports scheduling repeat cesarean at 40 weeks rather than waiting longer, as:
- Women who reach 40 weeks without spontaneous labor face substantially higher TOLAC failure rates 4
- Failed TOLAC carries higher maternal morbidity than either successful VBAC or scheduled cesarean 2
Context-Specific Indications for Repeat Cesarean
Absolute indications for scheduled repeat cesarean (rather than TOLAC) include 1, 2:
- Multiple previous cesareans (women with several cesareans may not have VBAC as an option) 1
- Classic (vertical) uterine scar from any prior cesarean 1
- Estimated fetal weight >4,500g, especially without previous vaginal delivery 2
- Supermorbid obesity (BMI >50) 2
Cumulative Risks with Multiple Cesareans
Each additional cesarean exponentially increases future pregnancy risks 1:
- Placenta previa: 9,17, and 30 per 1,000 women with one, two, and three or more cesareans respectively 1
- Placenta accreta: 12.9 per 10,000 after one cesarean, 41.3 per 10,000 after two cesareans, and 217 per 10,000 (2.17%) after four cesareans 5, 1
- Surgical complications: Dense adhesions and bladder injury occur more frequently with three or more previous cesareans 6
Critical Pitfall to Avoid
Never schedule elective repeat cesarean before 39 weeks unless specific maternal or fetal indications exist, as this significantly increases neonatal respiratory morbidity 2. The 39-40 week window represents the optimal balance between fetal maturity and avoiding spontaneous labor complications.
Alternative: VBAC Consideration
For women who meet criteria and prefer TOLAC, approximately 74% achieve successful vaginal delivery 3, 7. However, women who experience prelabor rupture of membranes (PROM) or reach ≥40 weeks gestation should have their delivery mode reconsidered, as these factors significantly increase TOLAC failure risk (PROM odds ratio: 4.47,95% CI: 2.07-9.63) 4.