When a man who is Rh-positive marries a woman who is Rh-negative, there will be incidence of

Analyze the question: A man who is Rh-positive marries an Rh-negative woman. The question asks what problem may result among their children.

Concept: Rhesus (Rh) factor incompatibility

• Rh-positive (Rh+) is dominant over Rh-negative (Rh-).
• If the father is Rh+ and the mother is Rh-, the baby can inherit the Rh+ gene from the father.
• An Rh+ baby in an Rh- mother is an incompatible pregnancy.

Step by step:

1. The mother (Rh-) carries a Rh+ foetus.
2. At birth, or during pregnancy complications, some foetal Rh+ blood enters the mother's circulation.
3. The mother's immune system sees the Rh antigen as foreign and produces anti-Rh antibodies.
4. In the first pregnancy, the effect is usually small because antibody levels are still low.
5. In later pregnancies with an Rh+ foetus, these antibodies cross the placenta and destroy the baby's red blood cells. This is haemolytic disease of the newborn (erythroblastosis fetalis).
6. The result can be severe anaemia, jaundice, miscarriage or still birth.

Checking the other options:

• B. Sicklers: Sickle cell is linked to the haemoglobin gene (HbS), not the Rh factor.
• C. Albinos: Albinism is a recessive gene for melanin production, unrelated to Rh.
• D. Living children: Many children can be born alive, so this is not the specific "incidence" the question is pointing to.

Answer: The Rh incompatibility can cause still births (or miscarriages), so the answer is A.

Exam tip: Remember the pattern "Rh- mother + Rh+ father → Rh+ baby → trouble". Whenever you see this in WASSCE, JAMB or NECO, think of antibodies, destruction of the baby's red blood cells, jaundice, still birth. The reverse (Rh+ mother, Rh- father) is not a problem.