Preterm labour
Preterm labour occurs during pregnancy when the uterus starts to contract before the 37th week of pregnancy, causing the cervix to open (dilate) and thin (efface).
The length of a normal pregnancy is 37 to 42 weeks, measured from the date of the mother's last menstrual period.
Early symptoms of preterm labour often are hard to diagnose. The uterus normally begins to contract around the 20th week of pregnancy. These early contractions (Braxton Hicks contractions) do not dilate or efface the cervix but help prepare the uterus and fetus for labour. These contractions can be mistaken for preterm labour.
Preterm labour is diagnosed in a woman who is 24 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 labour that leads to delivery is considered a miscarriage (spontaneous abortion).
| Author: | Jan Nissl, RN, BS | Last Updated: September 26, 2006 |
| Medical Review: | Renée M. Crichlow, MD - Family Medicine Liisa Honey, MD, FRCSC - Obstetrics and Gynecology Adam Husney, MD - Family Medicine Peter J. Kahrilas, MD - Gastroenterology | |
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