Question

Rh incompatibility in first pregnancy occurs when (a) Foetus develop its heart completely (b) During the delivery of first child (c) When foetal organs completely develop (d) Never occur in the first pregnancy

Short answer

Rh incompatibility in the first pregnancy occurs during the delivery of the first child (Option b).

Step-by-step solution

Understanding Rh factor

The Rh factor is a type of protein on the surface of red blood cells. Most people are Rh positive. Those who do not have the Rh factor are Rh negative. Rh incompatible pregnancy occurs when the mother is Rh negative and the baby is Rh positive.

Match the conditions with understanding

Now, given the multiple-choice options, only option b ('During the delivery of the first child') is consistent with our understanding of when Rh incompatibility can occur. This is because during the delivery of the first child, the mother can be exposed to the baby's Rh positive blood.

Validate the chosen option

Double-checking our selection, we find that options a, c and d do not particularly relate to the mother's exposure to Rh positive blood, and thus are not likely to be conditions under which Rh incompatibility arises in a first pregnancy. So, the remaining viable answer is option b.

Key concepts

Rh Factor Pregnancy

The Rhesus (Rh) factor is an important consideration during pregnancy because it can lead to Rh incompatibility, a condition that happens when an Rh negative mother is pregnant with an Rh positive baby. When the mother's and baby's blood systems are separate, there is generally no issue. However, during childbirth, the mother's and baby's blood can mix, exposing the mother to the Rh positive antigen.

Her immune system might recognize these foreign cells and start producing antibodies against them. While this usually does not affect the first pregnancy, it can pose risks for future pregnancies with Rh positive babies.

For Rh negative mothers, obstetricians often recommend receiving Rho(D) immune globulin, which prevents the development of these antibodies. It's crucial for the mother to receive this medication during her first pregnancy to prevent any sensitization that could make future pregnancies more complicated.

Rh Positive Blood

Possessing Rh positive blood means that there are specific proteins, called Rh antigens, located on the surface of the red blood cells. Most of the world's population, about 85%, has Rh positive blood. When two Rh positive parents conceive, the child will almost certainly be Rh positive as well. However, because the Rh positive gene is dominant, it's also possible for an Rh positive parent and an Rh negative parent to have an Rh positive child.

Having Rh positive blood does not usually lead to complications during pregnancy unless the mother is Rh negative. In such cases, appropriate steps are taken to ensure a safe pregnancy and delivery if the child is Rh positive. It's important for pregnant women to know their Rh status as part of prenatal care.

Rh Negative Blood

Individuals with Rh negative blood do not have the Rh factor protein on their red blood cells. This group is less common, with only about 15% of the population being Rh negative. When it comes to pregnancy, a mother who is Rh negative is at risk for Rh incompatibility if carrying an Rh positive child.

In an Rh incompatible pregnancy, the absence of the Rh factor in the mother's blood can cause her immune system to develop antibodies against Rh positive cells. This most commonly occurs during the delivery of an Rh positive baby, as the mother's and baby's blood can mix during birth. If these antibodies develop, they can cross the placenta in subsequent pregnancies and attack the red blood cells of an Rh positive fetus, leading to hemolytic disease of the fetus and newborn (HDFN), which can be dangerous.

Pregnant women with Rh negative blood should receive Rho(D) immune globulin at around 28 weeks of pregnancy and after any event where fetal blood might enter the maternal circulation, such as delivery, miscarriage, or invasive prenatal testing. This preventive treatment is key to a safe pregnancy and the health of future pregnancies.