Duedate Accuracy

Hello Po Mga Ka-nanay! Ano Po Ba Yung Usually Na Nasusunod Or Mas Malapit Sa Duedate? First Ultrasound (aorund 20 weeks) - December 21 Second Ultrasound - December 26 Third Ultrasound - December 24 Pwede po kaya na lumabas na si baby around first week of December? Thank you po :)