Elevated first trimester PAPP--a is associated with increased risk of placenta accreta

The objective of this article is to determine whether there were differences in first trimester serum analytes between cases of placenta previa with and without accreta.

Cases of placenta previa in which the patient had first trimester aneuploidy screening were identified. Pregnancy-associated plasma protein A (PAPP-A) and free beta human chorionic gonadotropin (fbhCG) MoMs were compared with those with an accreta. Accreta cases were also compared with published distributions to determine significance and to develop likelihood ratios based on MoM values.

Eighty-two cases of previa were identified, including 16 with a histological diagnosis of placenta accreta. The median PAPP-A MoM of 1.68 in accreta was significantly greater than that of 0.98 in non-accreta (P = 0.002). For fbhCG, the median MoM was 1.00 and 1.01 in accreta and non-accreta, respectively. Of the 16 patients with accreta, 14 (87.5%, 95% confidence interval: [61.6%, 98.4%]) had PAPP-A MoM above 1.0. Six of 16 (37.5%) accreta cases were above the 90th percentile of the unaffected distribution. The likelihood ratios for accreta were 0.5, 2.0, and 3.0. PAPP-A MoMs were 0.19, 2.11, and 4.27, respectively.

First trimester PAPP-A levels may be useful in identifying pregnancies at high risk for placenta accreta. Larger studies could incorporate both clinical and biochemical data into a risk algorithm.