Having occasional mild to moderate abdominal pain is normal throughout pregnancy . The pain is often more severe in women carrying twins than in single pregnancies. Severe pain with or without certain other symptoms may indicate a number of serious complications .
Menstrual-like abdominal cramps that come and go are one of the earliest symptoms of pregnancy , often occurring even before you notice the missed period and a home pregnancy test shows positive results. It is generally accompanied by other symptoms like spotting (implantation bleeding) fatigue, breast tenderness, nausea and constipation  in the first months.
With the growth of the embryo, the uterus begins to tilt towards the right, causing the ligaments to stretch or contract. This often leads to lower right abdominal pain and cramping .
The ICD-9 code used for indicating abdominal pain is 789.0  while its ICD-10 code is R10 .