16 weeks gestation: Mean biparietal diameter (BPD) is 3.62 ± 0.58 cm; mean abdominal circumference is 10.32 ± 1.92 cm; mean femur length is 2.10 ± 0.51 cm.
17 weeks gestation: Mean BPD 3.97 ± 0.44 cm, mean OC 11.49 ± 1.62 cm, mean FL 2.52 ± 0.44 cm.
18 weeks gestation: BPD average 4.25 ± 0.53 cm, AC average 12.41 ± 1.89 cm, FL average 2.71 ± 0.46 cm.
19 weeks gestation: BPD average 4.52 ± 0.53 cm, AC average 13.59 ± 2.30 cm, FL average 3.03 ± 0.50 cm.
28 weeks gestation: BPD average: 7.24 ± 0.65 cm; ABW average: 22.86 ± 2.41 cm; FL average: 5.35 ± 0.55 cm.
29 weeks gestation: BPD average: 7.50 ± 0.65 cm; ABW average: 23.71 ± 1.50 cm; FL average: 5.61 ± 0.44 cm.
Week 30: BPD (biparietal diameter) average: 7.83 ± 0.62 cm; ABU (abdominal circumference) average: 24.88 ± 2.03 cm; FL (femur length) average: 5.77 ± 0.47 cm.
Week 31: BPD (biparietal diameter) average: 8.06 ± 0.60 cm; ABU (abdominal circumference) average: 25.78 ± 2.32 cm; FL (femur length) average: 6.03 ± 0.38 cm.