Prometrium Side Effects

I have read over the internet that the use of Prometrium cooperatively timed with the menstrual cycle (peak +3 through peak +12) while using NFP may relieve bleeding and menstrual pain. Your site seems to state this also.
However, the manufacturer of Prometrium (Solvay) has the following statement listed on their internet site under side effects:

http://www.solvaypharmaceuticals-us.com/Products/Womens_Health/PROMETRIUM/Safety/Contraindications and Side Effects

* Patients who may be allergic to or have known sesitivities to peanuts should not take Prometriumr Capsules.

* Transient dizziness may occur in some patients; they should use caution when driving a motor vehicle or operating machinery. A small percentage of women may experience extreme dizziness and/or drowsiness during initial therapy. For these women, bedtime dosing is advised.

* Common side effects of PROMETRIUMR Capsules when given alone for secondary amenorrhea are dizziness, abdominal cramping, headache and breast pain. The most frequently occurring adverse events in women taking estrogen(0.625mg/d) and cyclic Prometrium Capsules( 200mg/d for 12d/mo) are: breast tenderness, dizziness, abdominal bloating, vaginal discharge, chest pain and diarrhea.

* PROMETRIUMR Capsules is not recommended for patients with known or suspected pregnancy, current or past history of thrombotic disorders, severe liver dysfunction or disease, known or suspected malignancy of breast or reproductive organs, undiagnosed vaginal bleeding, missed abortion, or as a diagnostic test for pregnancy.

* PROMETRIUMR Capsules is rated Pregnancy Category B.

I have highlighted the pertinent text above that concerns me (… not recommended for patients with known or suspected pregnancy, …missed abortion, …Pregnancy Category B). These warnings seem to indicate a concern with taking such medication if the patient was pregnant. What is the concern here… abortive, birth defects, or other? If abortive, this medication would seem to be in violation to the desired moral principle. Please explain what the side effects listed above mean exactly, and answer whether an abortive effect is increased at all by use of this medication.

Thanks, Joe