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When does labor usually start?

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​The due date is 40 weeks after the first day of the last menstrual period, although sometimes it is determined by an ultrasound. For most women, labor occurs sometime between week 37 and week 42 of pregnancy. Labor that occurs before 37 weeks of pregnancy is considered premature, or preterm labor. Labor that occurs at 37 or 38 weeks is now considered early term because babies born at that gestational age are still immature.

Just as pregnancy is different for every woman, the start of labor, the signs of labor, and the length of time it takes to go through labor will vary from woman to woman and even from pregnancy to pregnancy.

Signs of Labor

Some signs that labor may be close (although, in fact, it still might be weeks away) can include1:

  • “Lightening.” This term describes when the fetus “drops,” or moves lower in the uterus. Not all fetuses drop before birth. Lightening gets its name from the feeling of lightness or relief that some women experience when the fetus moves away from the rib cage to the pelvic area. This allows some women to breathe easier and more deeply and to get relief from heartburn.
  • Increase in vaginal discharge. Called “show” or “the bloody show,” the discharge can be clear, pink, or slightly bloody. This occurs as the cervix begins to open (dilate) and can happen several days before labor or just as labor begins.2

If a woman experiences any of the following signs of labor at any point in pregnancy, she should contact her health care provider3:

  • Contractions every 10 minutes or more often
  • Change in color of vaginal discharge
  • Pain or pressure around the front of the pelvis or the rectum
  • Low, dull backache
  • Vaginal spotting or bleeding
  • Abdominal cramps, with or without diarrhea

Sometimes, if the health of the mother or the fetus is at risk, a woman’s health care provider will recommend inducing labor, using medically supervised methods, such as medication, to bring on labor.4

Unless earlier delivery is medically necessary, waiting until at least 39 weeks before delivering gives mother and baby the best chance for healthy outcomes. During the last few weeks of pregnancy, the fetus’s lungs, brain, and liver are still developing.5

The Is It Worth It? Initiative, from the NICHD’s National Child and Maternal Health Education Program, focuses on raising awareness of the importance of waiting until at least 39 weeks to deliver a baby, unless it is medically necessary to deliver earlier.

  1. Office of Women’s Health. (2010). Pregnancy—Labor and birth. Retrieved July 22, 2013, from [top]
  2. American College of Obstetricians and Gynecologists. (2011). FAQs: How to tell when labor begins. Retrieved July 22, 2013, from Web Site Policy (PDF – 188 KB) [top]
  3. March of Dimes. (n.d.). Get ready for labor. Retrieved July 22, 2013, from Web Site Policy [top]
  4. American College of Obstetricians and Gynecologists. (2012). FAQs: Labor induction. Retrieved July 22, 2013, from Web Site Policy (PDF – 234 KB) [top]
  5. National Children and Maternal Health Education Program. (2013). Information for moms to be. Retrieved July 31, 2013, from [top]

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