**Core Concept**
The transfer of antibodies from mother to fetus is an essential immunological process that provides protection to the newborn against infections. This process occurs through the placenta, where maternal IgG antibodies are transported across the placental barrier and into the fetal circulation.

**Why the Correct Answer is Right**
IgG antibodies are the primary immunoglobulins transferred from mother to fetus. These antibodies are produced by the mother's immune system in response to infections or vaccinations and provide passive immunity to the fetus. The placenta contains specific receptors that facilitate the transfer of IgG antibodies from the maternal circulation into the fetal circulation, ensuring the fetus is protected against infections during the prenatal period.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because IgM antibodies are not transferred from mother to fetus due to their larger size and inability to cross the placental barrier.
**Option B:** This option is incorrect because IgE antibodies are involved in allergic reactions and are not transferred from mother to fetus.
**Option C:** This option is incorrect because IgA antibodies are primarily found in mucosal secretions and are not transferred from mother to fetus.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the transferred antibodies from mother to fetus provide protection against infections during the first six months of life, but the baby's own immune system will eventually take over, and the transferred antibodies will be gradually eliminated.

**Correct Answer:** D. IgG