Table 1 Protocol for re-dating the pregnancy by ultrasound
Biometric measurements | Gestational age by u/s | Accuracy | Criteria for re-dating |
|---|---|---|---|
BPD and FL | < 20 weeks | ± 7 days | Pregnancy re-dated by u/s if measurements > 7 days different from menstrual dates |
BPD, FL, & AC | 20 to 28 weeks | ± 14 days | Pregnancy re-dated by u/s if measurements > 14 days different from menstrual dates |
BPD, FL, & AC | > 28 weeks | ± 21 days | Pregnancy re-dated by u/s if measurements > 21 days different from menstrual dates |