Blood clots are not a common effect in the fetus due to Rh incompatibility. A disorder known as erythroblastosis fetalis is a type of hemolytic disease that occurs in the fetus due to an immune reaction of the Rh negative mother and an Rh positive fetus. All other choices are associated with this type of incompatibility.

A missed abortion is marked by the death of the fetus in utero but is not expelled from the uterus. If left untreated can lead to infection in the womb, it is marked by foul odor and bleeding as well as an elevated temperture and sepsis. 

A hydatidiform molar pregnancy is mostly a benign process that may occur due to an abnormal ovum becoming fertilized and growing into collection of cells in a cluster like formation. They are benign over 80% of the time. Rho-D immune globulin is a medication administered to an Rh negative mother that will give birth to a second Rh positive child to prevent an immune reaction that may harm the child. 

Magnesium sulfate is used to prevent seizures in women with severe preeclampsia. Calcium gluconate is the antidote if magnesium toxicity is assessed. It should be readily available when a woman is receiving magnesium sulfate. Pitocin is used to stimulate the uterus, often to induce labor. Nubain is an opioid that can be given to women during labor to treat pain. Zolpidem (Ambien) is a sleep aid. 

Yoga once per week (light exercise) is the least likely of the above to cause a change in regular menstruation. Cross country or long distance running (vigorous exercise) is more likely to cause changes to a woman's cycle. Poor lifestyle choices such as eating habits and health issues such as kidney disease can also cause irregular menstruation. Likewise, pharmaceuticals can have the same effect.

Metrorrhagia is bleeding between periods. Menorrhagia refers to excessively heavy periods. Oligomenorrhea refers to light, scattered periods (typically spaced by greater than 35 days). Polymenorrhea is used to describe short cycles of equal to or less than 21 days. Menometrorrhagia is used to describe periods that are heavier, sporadic, and more frequent than normal periods. 

According to the family planning method of contraception, the period in which conception can occur and one should refrain from intercourse is up to 7 days before and 7 days after ovulation. Some references show that sperm can live for up to five to seven days inside the female reproductive system. An unfertilized egg can live from between 12-24 hours. This greatly increases the window in which conception can occur. 

Oral contraceptives may increase the risk of breast cancer, increase the risk of depression, and increase the risk of developing a blood clot (higher in women who smoke cigarettes). They can reduce the risk of uterine cancer and are frequently used in women with primary dysmenorrhea. Primary dysmenorrhea refers to painful menstrual cycles without an underlying cause. 

Amenorrhea is the complete absence of a period. There are many different causes for amenorrhea. One of the most frequent causes of amenorrhea for women in the fifth decade of life, is menopause. Menopause is the most likely  cause of amenorrhea in this particular patient because she has not been experiencing periods for 12 months and is 51-years-old. While pregnancy is possible, the nurse would suspect menopause first. Pelvic inflammatory disease (PID) is a pelvic infection usually resulting in severe pain. Endometriosis is a condition in which uterine tissue inappropriately grows in areas such as the rectum or ovary, also typically causing severe pain. Polycystic ovarian syndrome is a condition causing hormone imbalance. It can cause amenorrhea. This question requires the use of strategy to answer. There are several choices that could be responsible for amenorrhea, but which one is the most correct?  

There are many different ways to treat painful periods (dysmenorrhea). Ibuprofen and naproxen are anti-inflammatory agents that do not require a prescription and can be very effective. They have relatively few side effects. Lifestyle modification (such as exercise) is another good alternative. The use of oral contraceptives are also frequently used to give women lighter and milder periods. Percocet is not generally used because it is an opioid analgesic and not recommended for long term use because they carry potential for addiction.