Twins!!

My wife and I did IUI. We struggled with our first baby. We did IUI

8 times and lost 2. Our first try after our little one being 14 months and we found out it’s twins. We are 6 weeks 5 days today. Monday we saw two but baby b had no flicker. We came back today and baby a had doubled. Baby b has a faint flicker but had also doubled in size. Baby a was 6 weeks 4 days and b was 6 weeks 1 day. They said baby b has 10 percent chance. Anyone else has this and had a great outcome?