(678) Timing of Maternal Serum Alpha Fetoprotein Testing in Pregnancy and Association With Adverse Perinatal Outcomes

Retrospective cohort study of patients receiving prenatal care at a single US tertiary center between 2013-2018. Included patients had a non-anomalous singleton fetus with MS-AFP as part of standard genetic screening at 15w0d-20w6d GA. The primary outcome was an APO composite of stillbirth, preeclampsia, fetal growth restriction, neonatal death, preterm delivery, placental abruption, accreta spectrum. Multivariable logistic regression models were used to compare the primary outcome between patients with elevated MS-AFP and normal MSAFP (0.5-< 2.5MoM), and receiver operator characteristic curves with area under the curve (AUC) assessed the predictive efficiency of MS-AFP values for composite APOs by week GA of test performance.


Results: Of 6870 included patients, 101 (1.5%) had elevated MS-AFP and 6769 (98.5%) had normal MSAFP. There were no significant differences in maternal age, body mass index, race/ethnicity and other baseline characteristics between patients with elevated and normal MS-AFP. Across all GA ranges, elevated MSAFP was significantly associated with increased odds of composite APO except at 20w0d-20w6d (Figure 1). However, tests of homogeneity did not reveal any significant difference in association across GA groups (p=0.95). When evaluating predictive efficiency, elevated MSAFP was a poor predictor of APO at each GA period (AUCs 0.59-0.69; Figure 2).

Conclusion: Elevated MS-AFP ≥2.5MoM is associated with similarly increased odds of APOs across 15w0d-20w6d GA.