**Core Concept**
In women with threatened abortion, the risk of various maternal adverse outcomes increases due to the underlying hormonal and physiological changes. Threatened abortion refers to vaginal bleeding in the first 20 weeks of pregnancy, which can be caused by hormonal fluctuations, genetic abnormalities, or other factors.

**Why the Correct Answer is Right**
Gestational diabetes mellitus (GDM) is not directly associated with threatened abortion. In fact, women with threatened abortion are at a lower risk of developing GDM, as the underlying pathophysiology involves hormonal changes that are not typically linked to insulin resistance or pancreatic beta-cell dysfunction. The other options, such as placenta previa, placental abruption, and manual removal of placenta, are all known complications of pregnancy that can be associated with threatened abortion.

**Why Each Wrong Option is Incorrect**
**Option A:** Placenta previa is a condition where the placenta partially or completely covers the internal cervical os, and it is a known complication of threatened abortion. The hormonal changes and bleeding associated with threatened abortion can lead to placenta accreta, which increases the risk of placenta previa.
**Option B:** Placental abruption is a condition where the placenta separates from the uterus, and it is also associated with threatened abortion. The bleeding and hormonal changes can disrupt placental implantation, leading to placental abruption.
**Option C:** Manual removal of placenta (also known as manual placenta extraction) is a procedure that may be required in cases of retained placenta, which can occur after a threatened abortion. The risk of retained placenta is higher in women with threatened abortion due to the underlying hormonal and physiological changes.

**Clinical Pearl / High-Yield Fact**
Women with a history of threatened abortion should be closely monitored for signs of placenta previa, placental abruption, and retained placenta, as these complications can be life-threatening.

**Correct Answer:**
✓ Correct Answer: D. Gestational diabetes