Most pregnancies proceed uneventfully. However, you should know what possible danger signs are so you can contact your doctor or hospital if you experience them.
If you experience any of the following signs, it's recommended that you call your doctor or go directly to the hospital to make sure you are taken care of.  

Signs and Symptoms of Danger in Pregnancy

Symptom Potential Problem
Pain in the lower abdomen Labor, miscarriage, ectopic pregnancy, abruption, ruptured uterus, degenerating fibroid, Cyst, uterine growth, ligament pain
Pain in the upper abdomen Liver problems, preeclampsia, gallbladder stones or infections, stomach problems, cardiac (heart) problems
Vaginal Bleeding Miscarriage, placental abruption, placenta previa, hHormonal bleeding, Implantation bleeding
Back Pain Miscarriage, preterm labor, Kidney/bladder infection, cyst, normal pregnancy pain  
Gush of Fluid from Vagina Preterm rupture of membranes, miscarriage, Urine from bladder, vaginal infection  
Swelling of the Hands/Face Pregnancy Induced Hypertension (PIH)  
Severe Headaches, Blurry Vision PIH, Ecclampsia  
Regular Contractions prior to 37 Weeks Preterm labor  
No Fetal Movement Fetal distress, Fetal Demise, Normal