They have been clamping our umbilical cords early since as early as the 1950's. This is what it means to clamp (ie prevent placental transfusion), the effects, and why they do it.

First off, to dispel all the "they don't do that!", yes, they do still clamp the umb!lical cord early. The problem has not been formally nor informally solved.
https://pubmed.ncbi.nlm.nih.gov/24215582/
https://pubmed.ncbi.nlm.nih.gov/29689745/

These are the effects.
Significant reduction in brain myelination:
https://www.jpeds.com/article/S0022-3476(18)31079-5/fulltext
At 4 months:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6259583/
And 12 months:
https://pubmed.ncbi.nlm.nih.gov/32702760/

Boys have lower fine motor and social scores at 4 years old.

Virginia Apgar's "Apgar score" encouraged clamping immediately after delivery.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3423128/

A review of placental transfusion:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5290307/

Role of ferritin (iron stores) in free radical defense and early neurodevelopment
https://chem.libretexts.org/Courses/Saint_Marys_College_Notre_Dame_IN/CHEM_342%3A_Bio-inorganic_Chemistry/Readings/Metals_in_Biological_Systems_(Saint_Mary's_College)/Iron_Storage%3A_Ferritin

https://www.who.int/elena/titles/cord_clamping/en/
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD004074.pub3/full?highlightAbstract=umbil%7Cumbilical
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD003248.pub4/full?highlightAbstract=umbil%7Cumbilical

The cord blood, placenta, and foreskin is parsed out and sold for exorbitant sums.
https://www.atcc.org/search#q=foreskin&sort=relevancy&f:contentTypeFacetATCC=[Products]
https://www.atcc.org/search#q=Umbilical&sort=relevancy&f:contentTypeFacetATCC=[Products]
https://www.atcc.org/search#q=cord%20blood&sort=relevancy&f:contentTypeFacetATCC=[Products]
https://www.atcc.org/search#q=placenta&sort=relevancy&f:contentTypeFacetATCC=[Products]

Youtube hides posts about early clamping.