What condition is a person with a previous cesarean section (CS) at a higher risk for in a subsequent pregnancy?

Risk of Placenta Previa After Previous Cesarean Section

A person with a previous cesarean section has a significantly higher risk of developing placenta previa in a subsequent pregnancy, with the risk increasing from 3% after one cesarean to 67% after five or more cesarean deliveries. 1

Understanding the Increased Risk of Placenta Previa

Previous cesarean section is a major risk factor for placenta previa in subsequent pregnancies. The evidence clearly demonstrates a dose-response relationship:

• The risk of placenta previa increases with each additional cesarean delivery 2:

  • 3% risk after first cesarean
  • 11% risk after second cesarean
  • 40% risk after third cesarean
  • 61% risk after fourth cesarean
  • 67% risk after fifth or more cesarean deliveries

• A retrospective analysis found that women with 1,2, and 3 previous cesarean sections had 2.2,4.1, and 22.4 times increased risk of developing placenta previa, respectively 3

• The incidence of placenta previa was significantly higher in women with previous cesarean section (1.31%) compared to those with an unscarred uterus (0.75%) 4

Placenta Accreta Spectrum Disorder (PASD)

When placenta previa occurs in a woman with previous cesarean delivery, there is a substantially increased risk of placenta accreta spectrum disorder:

• The incidence of PASD has increased from approximately 1 in 2,500 to 1 in 500 deliveries, largely attributed to the increased rate of cesarean deliveries 2

• The risk of placenta accreta increases dramatically when placenta previa occurs in women with previous cesarean deliveries 2:

  • 0.3% risk with one previous cesarean without previa
  • Increases to 6.74% for women with five or more cesarean deliveries

• The percentage of placenta accreta increases linearly from 4.1% in patients with no previous cesarean to 60% in patients with three or more cesarean deliveries 5

Clinical Implications and Management

The increased risk of placenta previa and associated PASD has significant clinical implications:

• Women with placenta previa and previous cesarean section have a 16% risk of requiring cesarean hysterectomy due to placenta accreta and severe hemorrhage, compared to 3.6% in women with placenta previa and an unscarred uterus 6

• Patients with placenta previa accreta have significantly higher incidence of postpartum hemorrhage and emergency hysterectomy compared to those with placenta previa alone 5

• High-risk cases should be delivered at facilities with appropriate resources and multidisciplinary expertise 1

Addressing the Other Conditions in the Question

Regarding the other conditions mentioned in the question:

1. Fetal macrosomia: The evidence provided does not establish a statistically significant association between previous cesarean section and fetal macrosomia in subsequent pregnancies.

2. Intrauterine growth restriction (IUGR): The evidence provided does not establish a statistically significant association between previous cesarean section and IUGR in subsequent pregnancies.

3. Urinary tract infection: The evidence provided does not establish a statistically significant association between previous cesarean section and urinary tract infection in subsequent pregnancies.

Conclusion

Among the conditions listed in the question (placenta previa, fetal macrosomia, IUGR, and urinary tract infection), the evidence clearly demonstrates that placenta previa is the condition with a statistically significant increased risk following cesarean section. This risk increases with each additional cesarean delivery and is associated with potentially life-threatening complications such as placenta accreta spectrum disorder.