Outcomes following the detection of fetal oedema in early pregnancy prior to non-invasive prenatal testing: a retrospective cohort study

Abstract

Objective: To investigate the incidence of structural and chromosomal abnormalities in cases of fetal oedema on early ultrasound prior to non-invasive prenatal testing (NIPT). Design: Retrospective cohort study. Setting: Tertiary obstetric ultrasound clinic in Melbourne, Australia. Population: Women undergoing pre-NIPT ultrasound examination from January 2013-November 2018 with fetal crown-rump length (CRL) of 28-43 mm. Methods: Cases of reported fetal oedema or increased nuchal thickness were included. Clinical information was collected from the clinic's patient management database. Oedema was subclassified as isolated nuchal oedema (>2.2 mm) or generalised oedema/hydrops by two operators blinded to pregnancy outcomes. Main Outcome Measures: Incidence of chromosomal or structural defects following the detection of fetal oedema. Results: We identified 104 cases of reported fetal oedema with a CRL between 28-44 mm. Nuchal oedema and generalised oedema were present in 40 (38.5%) and 64 (61.5%) cases respectively. Outcomes were available in 93 cases (89.4%). Relevant chromosomal anomalies were identified in 21.5% (20/93), occurring in 12.1% (4/33) of the nuchal oedema and 26.7% (16/60) of the generalised oedema/hydrops cases. Structural anomalies with normal karyotype were found in an additional four (4.3%) cases. Miscarriage occurred in four (4.3%) cases and termination of pregnancy in 18 cases (19.4%). Oedema resolved by 11-13+6 weeks in 81.9% and these cases had less adverse outcomes than those with NT[?]3.5 mm (10.9% vs 76.5%, p<0.001). Conclusions: Fetal oedema in early pregnancy is associated with a high incidence of structural or chromosomal abnormalities, and these rates increase with progressive severity.