This calculator can be used to assess whether there is significant discordance in the growth in a twin pregnancy. The smaller twin is assessed against the larger twin. Discordance of 15% (calculation equals 85% ) requires referal for further investigation. Discordance of 25% or more (calculation equals 75% or below) requires direct referal to the RVI. Any additional abnormalities such as abnormal amniotic flid volume, abnormal dopplar or ascites requires similar referal.
This calculator provides a percentage of the smaller parameter over the larger parameter.

Programme written by DJR Hutchon.

Ultrasound measurements
1st twin = mm
2nd twin = mm

Smaller parameter is = % of larger parameter
Advice is

This calculator is for educational use. It is believed accurate but no responsibility for accuracy of the results is accepted by the author. David J R Hutchon BSc, MB, ChB, FRCOG Consultant Gynaecologist, Memorial Hospital, Darlington, England.
You are welcome to keep this page and use the calculator off-line.
Reference Advice from Mr Steve Strugis and Mr Ben Ononeze