Revisiting absent nasal bone in the second trimester.

PURPOSE

To evaluate the outcomes of fetuses diagnosed with absent nasal bone in the second trimester.

METHODS

This prospective, observational study included all fetuses who were diagnosed at or referred to our fetal medicine center with an absent nasal bone from 16 weeks onwards from November 2017 to December 2019. Amniocentesis for fetal karyotype and microarray was offered to all women. Women who opted not to undergo invasive testing were also followed up and neonatal outcome noted.

RESULTS

26 fetuses were eligible for inclusion in the study. 8 (30.8%) out of these were diagnosed with aneuploidy: 7 with trisomy 21 and one with trisomy 18. All fetuses with aneuploidy had additional ultrasound abnormality and/or high risk on biochemical screening.

CONCLUSIONS

Isolated absent nasal bone in the second trimester with prior low risk on combined screening performed by certified sonographers is unlikely to be associated with Down syndrome.