Procedures
The ultrasound database was searched for the terms “oedema”, “edema” and for increased nuchal translucency measurements in the reports of all pre-NIPT ultrasound examinations. Cases of singleton pregnancy with a CRL between 28 mm and 44 mm were then selected for analysis. Early fetal oedema was classified into two groups (see figure 1):
  1. Nuchal oedema (figure 1B) – increased oedema in the region of fetal neck > 2.2 mm (95th percentile for nuchal translucency measurement at 10 weeks of gestation7).
  2. Generalised oedema (figure 1C) – generalised subcutaneous oedema or fetal hydrops (subcutaneous oedema with at least one of pleural effusion, pericardial effusion or ascites).
De-identified images and videos of cases with fetal oedema were reviewed and classified independently by two operators with extensive experience in obstetric ultrasound, both blinded to the outcomes. In case of discordance, a third operator’s opinion was requested.
Cases of multiple pregnancy, missed miscarriages, CRL below 28 mm or above 45 mm or nuchal thickness less than 2.2 mm and without other signs of fetal oedema were excluded. Ultrasound examinations were performed using Voluson E10 (GE Healthcare Ultrasound, Zipf, Austria) machines, equipped with a 3D 4-8 MHz probe for transabdominal and a 5-9 MHz probe for transvaginal examinations.