"percentage funneling: funnel length/(functional cervical length + funnel length) ref"
"shape of funneling: T-shaped, Y-shaped, V-shaped or U-shaped 5. U-shaped funneling have a higher risk of preterm delivery 4"
"depth and width of the funnel: V-shaped funnel has a depth with no width; however, U-shaped funnel has the width as an important parameter"