Babies- how do they develop their blood type? What are some determing factors?

Question

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Answer 1

Their blood type is genetically determined at conception, with the A and B genes dominant, and O recessive to both. If a person has two O genes, they will have blood type O. If they have one O gene and either an A or a B gene, they will be A or B, depending on the one they have. If they have 2 A or 2 B genes, they will be A or B, and if they have 1 A and 1 B, they will be type AB.

Similar with the rhesus factor. Rhesus positive is dominant to rhesus negative, so more people will have positive.

The baby and the mother never share blood. They can have completely different blood types, which would destroy the blood of the baby and the mother if it was shared.

Answer 2

they develop them over time when their own cardiovascular system develops after birth. At first, they share the blood of the mother through the placenta during development, and they develop their own after 3-5 months after birth. A big determining factor is genetics.