Routine antenatal ultrasound: a retrospective audit.

Of 1021 maternity patients 92.6% had at least one ultrasound scan during pregnancy. Eighty-six point two percent of all patients were scanned before 26 weeks gestation. Ultrasound scanning before 26 weeks gestation resulted in dates being changed by two weeks or more in 14.3%. Ultrasound scanning was an important factor in later pregnancy management in 12% of patients and this figure justifies routine antenatal ultrasound at 16-20 weeks gestation.