Hemoglobin F is the primary carrier of oxygen to the fetus and is also called fetal hemoglobin. It helps in carrying oxygen from the mother's blood to the tissues and organs of the fetus. It is synthesized at the sixth week of pregnancy and continues to be high even after birth until the child is about two to four months old. It is composed of two subunits, namely two alpha and two gamma subunits.
Hemoglobin F - An Overview
The primary protein that transports oxygen in the developing human fetus is fetal hemoglobin. For a detailed review, read the below article.