I am in the 20th week of my third pregnancy, and I began having Braxton-Hicks contractions over the past couple of weeks. They can be quite strong at times. They are 30 seconds to one minute in duration. My doctor says not to be concerned, as both my previous pregnancies were normal and the babies came on or around their due dates. Should I be concerned?

--M.T.

Braxton-Hicks contractions are painless contractions that occur at irregular intervals -- although they do not hurt, they can be felt nonetheless. They were first described in 1872 by J. Braxton Hicks. Braxton-Hicks actually begin very, very early in pregnancy; contractions have been seen with ultrasound in the first trimester! They may be stimulated by massaging the uterus. These irregular contractions do not cause the cervix to soften or to dilate, nor do they increase the risk of preterm delivery. As pregnancy progresses, Braxton-Hicks contractions may become more frequent and stronger, although they are still irregular and rarely painful.

Contractions that lead to labor, defined as regular contractions that produce thinning or dilating of the cervix, generally produce more discomfort -- or outright pain -- and occur at regular intervals. Usually, as labor begins, contractions will be fairly far apart; gradually the interval between contractions will lessen until they are three to five minutes apart. If regular 10-15 minute contractions occur before 37 weeks of pregnancy, you should notify your doctor immediately, as these may be a sign of preterm labor. At term, many obstetricians recommend staying at home until the contractions have been five minutes or less apart for one hour -- always follow your own doctor's directions, however.

At any point in the pregnancy, if you are worried about these Braxton-Hicks contractions, see your doctor. A quick exam to check your cervix can reassure you that the contractions you are feeling are not the real thing.