Incidence of Placenta Accreta Spectrum Among Primigravid Women
The incidence of placenta accreta spectrum (PAS) among primigravid women is extremely low, approximately 0.3% or less, as first-time pregnant women lack the primary risk factor of prior uterine surgery. 1
Understanding the Baseline Risk in Primigravidas
The overall incidence of PAS in the United States is currently 1 in 272 birth-related hospital discharges, representing a dramatic increase from historical rates of 1 in 2,510 to 1 in 4,017 pregnancies. 2, 1 However, this population-level statistic is heavily skewed by high-risk patients with prior cesarean deliveries and other uterine surgeries.
For primigravid women specifically, the risk is substantially lower because they lack the most significant risk factor: prior cesarean delivery. 1, 3 The evidence demonstrates that:
- In the general population without placenta previa, the risk of PAS is approximately 0.3% with one prior cesarean delivery. 1
- This 0.3% figure represents women who have already had one uterine surgery, meaning primigravidas without any prior uterine intervention would have even lower baseline risk. 1
Risk Stratification for First-Time Mothers
While primigravid status confers protection, certain risk factors can still elevate PAS risk even in first pregnancies:
- Placenta previa alone (without prior cesarean) carries a 3% risk of PAS. 1, 4
- In vitro fertilization is an independent risk factor that can affect primigravidas. 1, 5
- Prior uterine curettage (such as for miscarriage management) increases risk even in first viable pregnancy. 1, 5
- Advanced maternal age and multiparity are additional factors, though multiparity by definition excludes true primigravidas. 2, 1
Critical Clinical Caveat
The absence of prior cesarean delivery does not eliminate PAS risk entirely. 5 Uterine body PAS can occur in primigravid women, particularly those with:
- History of uterine curettage for pregnancy loss 5
- Asherman's syndrome 1, 5
- Prior myomectomy with endometrial cavity entry 6
- Endometritis history 5
- Uterine leiomyoma 5
These cases are particularly dangerous because they are easily missed on prenatal ultrasound, with only 3% diagnosed pre-symptomatically, and up to 45% presenting with signs of uterine rupture even before 24 weeks viability. 5
Location-Specific Considerations
The incidence data provided reflects U.S. population statistics. 2, 1 The specific location mentioned in your question would require local epidemiological data, as PAS incidence varies based on:
- Regional cesarean delivery rates (the primary driver of PAS incidence) 3, 7
- Access to assisted reproductive technologies 7
- Maternal age demographics 7
- Prevalence of prior uterine procedures 7
In summary, primigravid women have the lowest risk profile for PAS, with incidence well below 0.3% in the absence of placenta previa or other uterine risk factors, but screening remains essential when any risk factors are present. 1, 3