Premature (pre-term) labor

Premature (pre-term) labor

A full term pregnancy lasts about 40 weeks. Premature labor (or pre-term labor) occurs when contractions begin to dilate the cervix before 37 weeks of pregnancy.

When preterm labor cannot be avoided, the baby is born earlier, which can be risky for his health. Babies born before term are more fragile and may suffer sometimes throughout their life from problems related to prematurity.

Although the causes of preterm labor are sometimes difficult to identify, there are certain precautions that can help prevent it.

Causes

The most common causes of preterm labor are:

  • Uterine bleeding. Certain conditions, such as preliminary cake (= the placenta implants and develops on the cervix), cause the fetal membranes to rupture, which triggers premature labor.
  • A stretch of the uterus. Multiple pregnancy (twins, triplets or more), along with excess amniotic fluid, causes the uterus to stretch, which can lead to uterine contractions and premature labor.
  • Bacteria or inflammation. An infection in the uterus can stimulate the production of substances that trigger pre-term labor.
  • Physical or psychological stress. Stress can cause hormones to be released which can trigger uterine contractions.

Prevalence

In Canada, the rate of premature births is around 8%, or one in 12 babies *. In France, this rate is slightly lower, around 7% *.

* (WHO data, 2010).

Premature labor is a common problem in pregnancy. It is attributed 75% of deaths in babies born without birth defects.

Diagnostic

  • La cervix length. The length of the cervix, measured by ultrasound during routine pregnancy check-ups, helps predict the risk of preterm labor. The shorter the cervix, the greater the risk of preterm labor.
  • La fibronectine. A few hours before labor begins, the fetal membranes change and release a substance called fibronectin. If this substance is only present in low concentrations in vaginal discharge, the risk of preterm labor is not high. However, even if the fibronectin concentration is high, this does not necessarily indicate that preterm labor will automatically occur.

Premature births on the rise

A recent WHO report1 indicates that in the majority of high-income countries, the rate of preterm births has increased in recent decades. In Canada, the rate of premature births is steadily increasing, from about 6% in the early 1980s2 at 8% in recent years3.

Late pregnancies (= pregnant women after 40) and the use of assisted reproduction techniques, such as IVF, have contributed to the increase in multiple births and premature deliveries. In some developed countries, the increase in the number of cesarean deliveries, or births initiated before labor by choice of some pregnant women, has also contributed to the increase in preterm births.

In underdeveloped countries, the main causes of preterm births are infections, malaria, HIV and the high rate of teenage pregnancies.

However, whether in rich or poor countries, a large number of preterm births remains unexplained.

 

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