Choice A rationale Vaginal bleeding during pregnancy can be a sign of a serious complication such as placenta previa or placental abruption. Placenta previa is a condition where the placenta partially or completely covers the cervix, which can lead to severe bleeding during pregnancy and delivery. Placental abruption is a serious condition in which the placenta separates from the uterus before the baby is born, which can cause heavy bleeding and can be life-threatening for both the mother and the baby. Therefore, any vaginal bleeding during pregnancy should be promptly reported to the healthcare provider. Choice B rationale Lightheadedness when lying on the back, also known as supine hypotensive syndrome, can occur in pregnancy when the enlarged uterus compresses the inferior vena cava, reducing blood return to the heart and causing a drop in blood pressure. While this can be uncomfortable, it is generally not considered a serious complication and can be alleviated by changing position. Choice C rationale Heartburn after eating is a common discomfort during pregnancy due to hormonal changes that relax the lower esophageal sphincter, allowing stomach acid to reflux into the esophagus. While it can be uncomfortable, it is generally not a sign of a serious complication. Choice D rationale Swelling of the ankles, also known as edema, is common in pregnancy due to increased fluid volume in the body. While it can be uncomfortable, it is generally not a sign of a serious complication unless it is sudden or severe, which could be a sign of preeclampsia.