There are 2 different ways to track a fertilized egg with an X-Ray, water or oil contrast liquid. Water and oil based contrast liquids both have their pros and cons, but it is evident that either liquid will work and both were tested to see if one was better than the other. Oil produced more pregnancies with the control group and water less. Though both oil and water based contrast worked, oil was 1% higher in effect than water. Both oil and water contrast seem to be viable options and there are still risks associated with both as pregnancy is never perfect.