Braxton hicks when pregnant
Painless tightenings, called Braxton Hick's contractions, start at the top of the fundus and travel down the uterus causing it to harden for about 30 seconds. This painless activity toward the end of pregnancy gave the uterus the practice it needed to contract strongly enough to expel a baby through the birth canal. The contractions also help direct more blood into the placenta during the last few weeks of pregnancy.
Although some women are completely unaware of having Braxton Hicks, for others they can become quite strong and uncomfortable toward the end of pregnancy. If this is the case for you, try changing your position, getting up and walking around, or having a warm ( !!! not hot) bath, since these simple remedies can help relax the uterine muscles. Practicing some breathing and relaxation techniques you are preparing for labor are also likely to be of benefit, as will back massage.
If this is your first pregnancy, it may be difficult for you to know whether you're having Braxton or early labor pains so the rule here is that if you are not sure, go to your midwife or OB for help. It is essential to report any prolonged or painful uterine activity immediately, especially if it is accompanied by lower backache, since you may be threatening to go into premature labor.
Another possible cause of uterine pain and low backache is placental abruption, which required urgent medical attention. In this condition the placenta starts to separate from the wall of the uterus. The underlying cause is unknown, but it is more common in cigarette smokers, cocaine and crack users, women with poor nutrition, or high blood pressure.