Background: Nuchal cystic hygroma is the most frequently identified marker of chromosomal anomalies during first trimester screening. Objective: To determine the association of the nuchal cystic hygroma with chromosomal anomalies diagnosed with karyotyping done between the first and second trimesters of pregnancy. Design: Retrospective study. Setting: Instituto Latinoamericano de Salud Reproductiva (ILSAR), Lima, Peru. Patients. Fetuses with nuchal cystic hygroma. Methods: The data were obtained from the ILSAR database between August 2007 and May 2018, the cases diagnosed by ultrasound from week 11 to 13.6. Nuchal cystic hygroma was defined as the presence of septated liquid content in the nuchal axial section with a thickness above the 95th percentile value for increased nuchal translucency value for the crown-rump length. The karyotype was obtained between the first and second trimeste...