Regular contractions during pregnancy

Regular contractions may indicate that you are experiencing a tightening of the uterine wall called Braxton Hicks contractions or that you are in labor. It may be difficult to tell the difference between Braxton Hicks contractions and true labor. If there is any doubt, call your health professional.

Braxton Hicks contractions

During the second and third trimesters of pregnancy, you may notice episodes when your belly tightens and becomes firm to the touch, then relaxes. These are episodes of tightening (contraction) of the uterine muscles called Braxton Hicks contractions. These normal contractions may be hardly noticeable or may be strong enough to make you stop what you are doing.

Considered "warm-up" exercises for the uterus, Braxton Hicks contractions can begin as early as the 20th week of pregnancy, although most often they start between the 28th and 30th week.

Braxton Hicks contractions are usually infrequent in mid-pregnancy. However, they can be more frequent during the 9th month, sometimes occurring as often as every 10 to 20 minutes. Braxton Hicks contractions usually occur fewer than 4 to 6 times per hour.¹

Braxton Hicks contractions:

• Usually disappear during exercise or activity (unlike true labor pains, which continue or increase with activity).
• Are more noticeable during rest.

Preterm labor

The length of a normal pregnancy is 37 to 42 weeks, measured from the date of the mother's last menstrual period. Preterm labor occurs before the 37th week of pregnancy.

Early symptoms of preterm labor often are hard to diagnose. Preterm labor is diagnosed in a woman who is 20 to 37 weeks pregnant and has regular uterine contractions that cause her cervix to:

• Open (dilate) at least 2 cm.
• Thin (efface) at least 80%.

Before 20 weeks, preterm labor that leads to delivery is considered a miscarriage (spontaneous abortion). If you are less than 37 weeks pregnant and have more than 4 contractions per hour, after an hour of resting and drinking fluids, call your health professional.

Early labor

Early labor is often the longest part of the birthing process, sometimes lasting 2 to 3 days. Uterine contractions:

• Are mild to moderate (you can talk while they are happening) and last about 30 to 45 seconds.
• May be irregular (5 to 20 minutes apart) and may even stop for a while.

In early labor, the cervix opens (dilates) to about 3 cm (1.2 in.).

First-time mothers may experience many hours of early labor without the cervix dilating. You may go to the hospital and be sent home again until you begin active labor or your water breaks (rupture of the membranes).

Active labor

The first stage of active labor starts when the cervix is about 3 cm (1.2 in.) to 4 cm (1.6 in.) dilated and is complete when the cervix is fully dilated and the baby is ready to be pushed out. During the last part of this stage (transition), labor becomes particularly intense.

Compared to early labor, the contractions during the first stage of labor are:

• More intense.
• More frequent, occurring every 2 to 3 minutes.
• Longer-lasting, lasting 50 to 70 seconds.

You may feel restless or excited during active labor. Now is the time to be at or go to the hospital or birthing center. If your bag of waters (amniotic sac) hasn't broken before this, it may now. If you have taken a labor class and learned how to do special breathing during contractions, you will want to begin the special breathing now.

Citations

1. Cunningham FG, et al. (2001). Maternal adaptations to pregnancy. In Williams Obstetrics, 21st ed., pp. 167–200. New York: McGraw-Hill.

Author:	Jan Nissl, RN, BS Susan Van Houten, RN, BSN, MBA	Last Updated July 23, 2004
Medical Review:	Joy Melnikow, MD, MPH - Family Medicine Kirtly Jones, MD - Obstetrics and Gynecology
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