Week of gestation 
Week 12-13: 0.3 - 1.0
Week 14-15 : 0.4 - 1.6
Week 16-17 : 1.4 - 6.5
Week 18-19 : 1.6 - 8.5
Week 20-21 : 2.1 - 13
Week 22-25 : 2.7 - 16  
Week 26-29 : 3.0 -18  
Week 30-33 : 3.6 - 22  
Week 34 : 5.1 -25 
Week 35 : 5.2 - 26.4
Week 36 : 8.2 - 28.1
Week 37 : 8.0 - 30.1
Week 38 : 8.6 - 38.0 
Week 39 : 7.2 34.3
Week 40 : 9.6 - 28.9