I think you have to make your own decision, but after looking into it myself and doing my research, we decided no definitely not. There is some perception that it's a bit of a scam - basically, you pay huge amounts of money, but in most cases, you can't actually use the cord blood collected from your own baby. You can't only donate it to someone else, much like bone marrow, if their child happens to be a match, and hope that because you are part of a registry that if your child ever needs cord blood that there will be a match for him/her. That's how a midwife explained it to me. Basically, you can't use your own cord blood because whatever anomalies are present in it (which might one day lead to a problem for your child) are still present in the collected blood. You actually need to use someone else's blood, which you can do if you are part of a cord blood bank, but only if there is a match. If there isn't a match, you don't get any benefit from it, even after you pay all that money (but that registry does make a load of money from you whether you even use that blood or not). I'm sure that's not always the case and certainly science is always changing which might enable you to use those stem cells for a wider variety of conditions, etc. But it seemed like a bit of a scam to me.
Apart from that, the real damage I felt was that it meant my baby didn't get all her blood. The blood in the placenta and cord at birth is actually not just excess blood, it's from your baby's body that gets pushed back into the cord and placenta with the force of being born. When you cut the cord prematurely to collect cord blood, you prevent them from getting all their blood. I found the blog below by a midwife really helpful in explaining it when we were trying to make a decision, but basically, the average baby has about 280ml of blood at birth. Cord blood collection requires at least 45 ml but on average about 90ml is collected. That's like almost a third of your baby's overall blood volume, which should be going back into their body so that they don't have to work overtime to produce more blood in those first few days. Baby's who don't have their cords cut prematurely before all the blood goes back in are at much less risk of developing anemia in the first few months, so it can have a significant effect on their health.
Now, it may be a different story if you have a history of things like leukemia in your family, which makes having access to stem cells a priority. The risks to baby's health in the immediate post-birth period may pale in comparison to greater risks down the line. But for us, I felt like the risk of my daughter developing a rare condition that would be treated by still fairly experimental stem cell procedures was very, very small. So it seemed much more important to make sure she got the full benefit of the placental and cord blood at birth to prevent things like anemia and give her the best start possible. So that's why we decided not to.
Here's that blog: https://midwifethinking.com/2011/02/10/cord-blood-collection-confessions-of-a-vampire-midwife/
