So say a little bit more about what that really means.

So when we are a fetus, we live on fetal hemoglobin.

So hemoglobin has four chains.

So when we are a fetus, we have alpha chain and gamma chain.

Now, the genetic problem is on the beta chain, which basically switches on when we are born.

Now, when we have a fetus, we don't have any signs of sickle cell disease, but we can genetically test someone or a fetus to identify that this fetus has the genetic mutation, the genetic problem, which means that this fetus will be affected by sickle cell disease.

Now the fetus inside the womb is still healthy.

So what are the major hurdles that are keeping this kind of in utero therapy from becoming more common?