One of the first changes to occur in the female body in preparation for a new baby is the release of additional female hormones like estrogen and progesterone. In addition to several other jobs, these hormones tell the uterus to expand. Once the uterus begins to grow, mild pregnancy cramping may occur, and this could be a first pregnancy symptom. Many women have no idea they are pregnant when these first cramps are felt and this can easily be misinterpreted as menstruation cramping.

Keep in mind that if your cramping is more severe than you expect, especially if the pain is on the right or left side, then you should see your doctor immediately because this could be a sign of a life-threatening condition called an ectopic pregnancy.

Prior to any uterine growth, the fertilized egg attaches itself to the wall of the uterus. This attachment may actually be felt as mild cramping as well. Along with this cramping, light spotting can occur, which can also add to the idea that the normal monthly cycle will start.

Here is a breakdown of when and why cramps may be felt during each trimester:

First trimester

• Implantation Cramping: Some women will experience cramping upon implantation. Implantation usually occurs 8-10 days after ovulation. You should not experience implantation cramping after a positive pregnancy test. However, many women have experienced cramping only to find that they are indeed pregnant shortly thereafter.
• Stretching Uterus: As your body prepares for the baby, your uterus will stretch and expand. The ligaments that support the uterus will stretch which may cause mild cramps.
• Miscarriage: Cramping during early pregnancy, especially accompanied by spotting or bleeding, is a warning sign of a possible miscarriage.
• Ectopic Pregnancy: An ectopic pregnancy is a serious condition and requires immediate medical attention. Signs of an ectopic pregnancy include cramping and abdominal pain (particularly on one side), spotting, or bleeding.
• Other Causes: Constipation or gas pains. Pregnant women often have problems with constipation and this can lead to uncomfortable cramping as well.

Second and third trimesters

• Fast Uterine Growth/Round Ligament Pain: Once the body has started the growth process, the uterus will grow until the baby is ready to live outside the womb. Your uterus will continue to expand which will stretch the ligaments that attach the uterus to the walls of the abdomen. These ligaments will be more flexible than normal, due to the additional hormones in the body, but not enough to prevent cramping.
• Preparing For Birth: During the pregnancy, the uterus may begin training for the birth ahead, known as the Braxton Hicks contractions. These mild contractions will feel very similar to a cramp and should be noted and followed just in case they turn into a real early labor situation. One of the most common reasons for going to the hospital in the third trimester, before birth, is due to false labor from the strength of the Braxton Hicks contractions.
• Labor: During early labor, cramping and back pain are common symptoms. If the contractions felt appear at regular, shortening intervals and increase in severity, you may be in labor and should check in with your doctor/midwife.

When to call the doctor 

While there are harmless reasons for cramping during pregnancy, there are also serious medical conditions and events that can start out as cramping. If cramping is accompanied by bleeding from the vagina or if it increases in strength over a period of time, the doctor/midwife should be called immediately.

You can rarely distinguish Braxton Hicks from labor contractions. So especially if you are under 37 weeks, you should always let your doctor know when you have regular cramps.