Maternal habits predisposing to preterm labor

Smoking and drug abuse are recognized risk factors for preterm labor. Anybody who experiences threatened preterm labor or has had actual preterm labor and delivery in a previous pregnancy and is using either should be strongly advised to quit. Of course, those patients who are abusing heroin are not asked to stop during pregnancy but are switched to a safer and better-controlled drug, usually methadone.

Cocaine increases the risk of placental abruption, which is associated with preterm labor and a very high rate of fetal loss.

Assessing risk of recurrence of preterm labor

A previous preterm labor should be regarded as a risk factor for preterm labor. If the factor that predisposed to preterm labor in the first instance is unidentified, then the risk of recurrence is considered to be substantial.

The overall risk ofpreterm delivery is around 10%. Once a woman has suffered a preterm birth, her risk rises to 15%. After three preterm births, the risk jumps to 45%.

Some experts now recommend regular (weekly or fortnightly) vaginal swabs from about 24 weeks of gestation for women at risk in order to detect any low grade asymptomatic genital tract infections. Such infections are considered to be legitimate risk factors. This may be done if there is a history of previous preterm labor and an absence of any identifiable risk factor. There is really no solid scientific evidence as to the benefit of this strategy.

Managing preterm labor

If the preterm labor occurs after 34 weeks, there is consensus that there is no need to interfere. Assessment of the labor and maternal and fetal conditions will be made. Labor will be allowed to proceed, unless there are obstetric contraindications (for labor or vaginal delivery), when delivery may be made by caesarean section.

If the preterm labor is before 34 weeks, efforts may be made to stop or, more realistically , delay labor, to achieve a few more valuable hours, days or, if lucky, weeks.

Suppressing labor (Tocolysis)

Labor suppression is medically termed ‘Tocolysis’. There are a number of medications that can be used to suppress contractions and therefore stop labor. These are not always successful and have a number of side-effects. There is evidence, albeit weak, that any one of them can prolong pregnancy for probably a maximum of 48 hours.

In fact, most experts agree that if the pregnancy continues for more than a few days, it would have done so anyway, with or without the medication. It is, however, very important to understand that the 48 hours or so that may be gained as a result of using these drugs could be extremely crucial for the baby's prospects, once he or she is born. We shall come back to this shortly.

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