Mo/di - We've had a smaller Baby B since our 20 week scan and today there is a 31% difference between A and B with B measuring 2 weeks behind which has been consistent. Today the MFM asked if we had done genetics testing and we had not - and she offered we do it now to rule out chromosomal issues like Downs. We were never told this could cause the twin to be smaller so not sure why today one of the mfm'S brought it up - we see a diff dr all of the time and it's their first time assessing our issues.