Is in‑vitro fertilisation (IVF) pregnancy an independent risk factor for post‑abortal placenta accreta, considering typical associated factors such as maternal age > 35 years, prior uterine surgery, multiple gestation, or placenta previa?

Is IVF Pregnancy a Risk Factor for Placenta Accreta Spectrum?

Yes, in vitro fertilization (IVF) is an independent risk factor for placenta accreta spectrum (PAS), with an approximately 6–9-fold increased risk compared to spontaneous conception, even after adjusting for other established risk factors such as prior cesarean delivery, placenta previa, maternal age, and parity. 1, 2, 3

Magnitude of Risk

• IVF confers an adjusted odds ratio of 8.7 (95% CI 3.8–20.3) for PAS in a large population-based cohort, and this association persists after controlling for the number of prior cesarean deliveries (adjusted OR 6.7,95% CI 2.9–15.6). 2

• In a Massachusetts tertiary center cohort, IVF pregnancies carried 5.5 times the risk of PAS (95% CI 3.4–8.7) compared to non-IVF pregnancies, adjusted for maternal age, nulliparity, and year of delivery. 3

• The absolute incidence of PAS in IVF pregnancies ranges from 2.2% to 2.5%, compared to 0.3–0.4% in spontaneous conceptions. 2, 3

IVF as an Independent Risk Factor

The critical clinical insight is that IVF-associated PAS occurs independently of the traditional risk factors:

• Among IVF pregnancies with PAS, there is a significantly lower prevalence of prior cesarean deliveries (22.6% vs. 64.2% in non-IVF PAS cases) and lower rates of placenta previa (19.4% vs. 44.4% in non-IVF PAS cases). 3

• This pattern suggests that IVF may predispose to PAS through a distinct pathophysiologic mechanism—likely related to abnormal initial placentation or endometrial receptivity—rather than through the classic pathway of uterine scarring and placenta previa. 4, 3

• IVF pregnancies with placenta previa show higher placental weights and less frequent small placentas compared to non-IVF previa cases, supporting the hypothesis that IVF-related PAS stems from aberrant implantation site selection rather than underlying uterine pathology. 4

Relative Clinical Importance

While IVF is a statistically significant independent risk factor, its clinical impact is substantially smaller than that of placenta previa and prior cesarean delivery:

• Placenta previa alone carries an adjusted OR of 94.6 (95% CI 29.3–305.1) for PAS. 2

• Prior cesarean delivery carries an adjusted OR of 21.1 (95% CI 11.4–39.2) for PAS. 2

• IVF carries an adjusted OR of 8.7 (95% CI 3.8–20.3) for PAS. 2

• The combination of placenta previa and prior cesarean delivery remains the dominant risk scenario, accounting for approximately 49% of all PAS cases and >80% of confirmed accreta cases. 1, 5

Clinical Implications for Surveillance

All IVF pregnancies warrant heightened vigilance for PAS, even in nulliparous women without prior uterine surgery:

• Targeted ultrasound evaluation for PAS should be performed in IVF pregnancies with placenta previa or low-lying placenta, ideally between 28–32 weeks gestation by an examiner experienced in PAS diagnosis. 1, 5

• Gray-scale ultrasound demonstrates 90.7% sensitivity and 96.9% specificity for detecting PAS, with multiple placental lacunae being the most strongly associated finding. 1, 5

• Key ultrasound markers include: loss of the normal hypoechoic retroplacental zone, retroplacental myometrial thickness <1 mm, disruption at the uterine serosa-bladder interface, and direct placental extension into myometrium or bladder. 1, 5

• Color Doppler findings include turbulent lacunar flow (most common), increased sub-placental vascularity, gaps in myometrial blood flow, and bridging vessels from placenta to uterine margin. 1, 5

Critical Pitfall to Avoid

The absence of ultrasound abnormalities does NOT exclude PAS in IVF pregnancies with clinical risk factors; imaging and clinical risk assessment must be integrated. 1, 5

• Even with negative ultrasound findings, the presence of IVF combined with placenta previa mandates preparation for possible PAS at delivery in a Level III/IV maternal care center. 1, 5

Management When PAS is Suspected in IVF Pregnancy

Immediate referral to a Level III/IV maternal care facility with a multidisciplinary team (maternal-fetal medicine, experienced pelvic surgeons, urologic surgeons when bladder involvement suspected, interventional radiologists, obstetric anesthesiologists, and blood bank with massive-transfusion protocols) is mandatory. 1, 5

• Planned cesarean hysterectomy at 34 0/7–35 6/7 weeks gestation with the placenta left in situ is the standard approach; manual removal of the placenta is absolutely contraindicated due to catastrophic hemorrhage risk. 1, 5

• Approximately 50% of patients who remain pregnant beyond 36 weeks require emergent delivery for hemorrhage, supporting the 34–35 week delivery window. 1, 5

Summary Algorithm for IVF Pregnancies

1. All IVF pregnancies: Maintain heightened awareness for PAS throughout pregnancy, particularly if placenta previa or low-lying placenta develops. 1, 2, 3

2. IVF + placenta previa or low-lying placenta: Perform targeted PAS ultrasound at 28–32 weeks by experienced examiner. 1, 5

3. IVF + suspected PAS on imaging OR IVF + placenta previa + any prior uterine surgery: Immediate referral to tertiary center with multidisciplinary PAS expertise. 1, 5

4. Confirmed or highly suspected PAS: Plan cesarean hysterectomy at 34–35 weeks with placenta left in situ; activate massive transfusion protocol. 1, 5