Did you know? Ultrasound is the best modality to look for fetal breathing movements. Fetal respiratory movements form one of five parameters of the fetal biophysical profile used to assess antenatal fetal well-being. At least one breathing episode lasting ≥ 30 seconds during 30 minutes of observation is considered normal breathing. You can now understand why we take at least 30 to 45 minutes to assess second and third-trimester pregnancy ultrasound. Anything less is considered suboptimal. Trans-