According to WebMD, lower back cramping is quite common in early pregnancy. It is estimated to occur in about half of all pregnant women. Hormone level changes and other changes that take place as the body prepares for childbirth are responsible for this symptom. Many women continue to experience a dull backache throughout the second and third trimesters, as well.
Kidspot explains that back cramping during the early phase of pregnancy is primarily related to hormones and body changes. As the body prepares for childbirth, joints and ligaments must loosen for delivery. The center of gravity shifts, causing a change in posture. These changes lead to lower back pain and cramping. As a woman’s belly continues to swell, lack of sleep and unusual positioning become another factor in pregnancy backaches. Some women find it difficult to get comfortable in their normal sleeping position.
The American Pregnancy Association lists backache among the possible signs of pregnancy. However, while lower back cramping is definitely a sign of early pregnancy in some cases, it is not the only reason that a woman of reproductive age experiences backaches. Many women experience lower back cramping as a premenstrual symptom. It is also caused by physical or mental strains and stress or by other injury.