(375) Elevated middle cerebral artery peak systolic velocity (MCA PSV) in fetuses with unexplained anemia

Middle cerebral artery peak systolic velocity (MCA-PSV) Doppler measurement is a highly sensitive tool for identifying moderate to severe fetal anemia. While various factors like isoimmunization, infections, genetic conditions and less commonly, twin-twin transfusion syndrome and twin-anemia polycythemia sequence can cause fetal anemia, sometimes the cause remains unidentified before birth.
Our study aimed to determine the incidence of unexplained prenatal fetal anemia and to assess the related perinatal outcomes.

Study Design:

An observational retrospective cohort study of all fetuses who underwent Fetal Blood Sampling due to MCA PSV >1.5 MoM at a tertiary fetal medicine center between 2007 and 2021. Fetuses were included if they had a moderate or severe anemia defined as hemoglobin (Hgb) deviation of  more than 20 gr/L above gestational age-adjusted mean with negative anemia workup (Parvovirus serologies, indirect coombs, maternal Hgb electrophoresis, parental molecular testing for alpha thalassemia and Kleihauer Betke test). Data collected encompassed indications for Doppler assessment, prenatal and postnatal data, neonatal outcomes, autopsy findings, placental pathology and genetic testing.

Results:

Overall, 383 fetuses had an MCA PSV >1.5 MoM and underwent subsequent FBS. Twelve fetuses (3.1%) had moderate to severe anemia of unknown perinatal etiology. The indications for Doppler assessment were a sonographic anomaly in all fetuses (8 with non-immune hydrops or polyhydramnios and 4 with other major structural anomalies, not typically associated with anemia). Postnatal investigations revealed rare anemia-causing factors in four cases, such as fetal Gaucher's disease, Pyruvate Kinase deficiency, KAT6A gene pathogenic variants, and Trisomy 21 with bone marrow failure. The survival was poor with 6 (50%) cases of perinatal death divided into two intrauterine death and four neonatal deaths.

 

Conclusion:

Unexplained anemia in pregnancies accounts for 3.1% of cases, potentially leading to adverse neonatal outcomes. Therefore, vigilant monitoring and close surveillance are advised for such pregnancies.