DURING THE SECOND AND THIRD TRIMESTERS, OVER 90% OF THE HEMOGLOBIN OF THE FETUS IS

• A. Hemoglobin A
• B. Hemoglobin F ✓
• C. Hemoglobin G
• D. Hemoglobin H
• E. Hemoglobin Z

During the second and third trimesters of pregnancy, the fetal circulatory system undergoes significant development to support the growing fetus. One crucial component of this system is hemoglobin, the protein responsible for transporting oxygen in the blood. In a developing fetus, there is a specific type of hemoglobin that plays a predominant role during this stage.

Identifying the Predominant Hemoglobin in Fetal Circulation

Hemoglobin F, also known as fetal hemoglobin, is the primary type of hemoglobin found in fetuses during the second and third trimesters of pregnancy. This specialized form of hemoglobin has a higher affinity for oxygen compared to adult hemoglobin (Hemoglobin A), which allows it to efficiently extract oxygen from the mother’s bloodstream through the placenta.

Function and Importance of Hemoglobin F

Hemoglobin F is crucial for fetal development as it ensures that an adequate supply of oxygen is delivered to the developing tissues and organs. Its presence in high concentrations during the later stages of pregnancy reflects its importance in supporting the rapid growth and maturation of the fetus.

Transition to Adult Hemoglobin

After birth, there is a gradual transition from producing predominantly Hemoglobin F to producing adult hemoglobin (Hemoglobin A). By around six months of age, most infants have very low levels of Hemoglobin F in their circulation as they switch over to producing primarily Hemoglobin A.

In summary, during the second and third trimesters of pregnancy, over 90% of the fetal hemoglobin is Hemoglobin F, which plays a vital role in ensuring proper oxygen delivery to support fetal growth and development.