The most critical period of its development is between three and seven weeks after fertilization, when a simple heart tube assumes the shape of a four-chambered heart. In fact, the heart actually begins beating by the 22nd day of life.
When you are 5 weeks pregnant, your baby's heart is made up of two tiny channels called heart tubes and they're already hard at work, beating to their own drummer (it will be weeks before those beats become coordinated).
I don't know if you had a 3 day transfer or a 5 day transfer, but here is a day by day breakdown for both.
– Day 1: The embryo will continue growing and developing. At this stage, it will turn from a 6-8 cell embryo to a morula.
– Day 2: It will turn from morula to blastocyst.
– Day 3: The blastocyst embryo breaks through the zona pellucida.
– Day 4: The blastocyst attaches itself to the maternal uterus.
– Day 5: Embryo implantation begins.
– Day 6: Embryo implantation continues.
– Day 7: Now, embryo implantation is complete.
I believe it was just the gestational sac. Then the following week at 6 weeks 1 day, my doc saw the yolk sacs as well on both babies (twins), and saw the hearts beating on the monitor. Ultrasound at 7 weeks showed their growth progress and we heard the hearts beating via ultrasound. So don't get discouraged. Every pregancy is different. So they may see the yolk sac and a heart beat next time you go for your ultra sound. Good Luck to you.
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