Causes of Preterm labor

To be able to have a clear understanding of what the term mean, it is worthwhile to explain the important landmarks:

In the United States, "Pre-term" describes the gestation period between 20 weeks and just under 37 weeks. The reference gestation in other parts of the world is 24 to just under 37 weeks.

If symptoms appear before 20 weeks (24 weeks) of gestation, this is a threatened miscarriage and not preterm labor.

37 completed weeks onwards is ‘Term’ and labor at any stage thence is in order. After 42 weeks, it becomes post-term (post-maturity).

"Term" therefore spans a period of five weeks- from 37 to 42 weeks. It is not a fixed date.

Recognizing preterm labor

Between 20 (24) and 37 weeks, if there are regular and painful uterine contractions accompanied by changes to the cervix, then this is preterm labor. In a few instances, the contractions are painless.

Other symptoms include low backache which may be quite distressing, a feeling of pressure in the pelvis and occasionally the passage of a mucous blood-stained discharge, popularly called a "show".

In well over half of expectant mother who have symptoms suggestive of preterm labor, examination reveals no cervical change whatsoever. Technically, this is not preterm labor, and almost all will resolve without any action. However, when symptoms are there even in the absence of supporting clinical evidence, observation in hospital is the preferred form of management. In those cases where the cervix is found to be already thinning and dilating, the outlook for continuation of the pregnancy is less favorable and many - probably the majority - will go on to deliver within hours and, at most, days

Causes of preterm labor

The cause is unidentified in the majority of pre-term labor cases. We therefore talk of risk factors; situations that might predispose to preterm labor rather than causes. There are a good number of risk factors that predispose to preterm labor. These include:

Fetal abnormality
Abnormalities of the womb or cervix
Multiple pregnancy - the greater the number of fetuses, the greater the likelihood of preterm labor
Excessive amounts of amniotic fluid (hydramnios)
Extremes of maternal age - the very young and the older mother (late thirties onwards) are more prone
Serious genital tract or systemic infection
Urinary tract infection (UTI)
Rupture of membranes
Fetal death. Death of the fetus is usually followed by the onset of labor within days.
Rupture of membranes
Fetal death. Death of the fetus is usually followed by the onset of labor within days.

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