Preterm labour

Published on 09/03/2015 by admin

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Last modified 09/03/2015

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Chapter 37 Preterm labour

Definition. Preterm or premature labour is the onset of regular painful uterine contractions accompanied by effacement and dilatation of the cervix after 20 weeks and before 37 completed weeks of pregnancy.

Incidence: Preterm labour occurs in 5%–10% of all deliveries.

Common complications in premature infants include respiratory distress syndrome, intraventricular haemorrhage, bronchopulmonary dysplasia, patent ductus arteriosus, necrotising enterocolitis, sepsis, apnoea and retinopathy of prematurity.

The frequency of major morbidity rises as gestational age decreases.

Ongoing advances in neonatal medicine have resulted in dramatically improved outcomes for preterm infants; however, there remains significant risk of long-term morbidity, such as cerebral palsy, developmental delay, visual and hearing impairment, and chronic lung disease.

Significance

• Prematurity is the cause of 75% of perinatal deaths and a major determinant of short-term and long-term morbidity in infants and children.

• Two-thirds of the perinatal deaths occur in the 30%–40% of preterm infants who are delivered prior to 32 weeks gestation.

Aetiology

Preterm labour may be classified as spontaneous or indicated.

Spontaneous preterm labour

• Spontaneous preterm labour occurs in the absence of overt maternal or fetal conditions necessitating delivery. It commonly occurs in the absence of an obvious cause, or may follow preterm premature rupture of the membranes or related diagnoses such as incompetent cervix.

• Risk factors associated with spontaneous preterm labour include a history of previous preterm birth, multiple pregnancy, polyhydramnios, urogenital tract infection, previous cervical surgery, uterine anomalies, periodontal disease, bleeding in the second trimester, extremes of age, smoking, low prepregnancy weight and pregnancies achieved through assisted reproductive technologies.

• Most women who deliver preterm have no apparent risk factors.

Indicated preterm labour

• Indicated preterm labour occurs when conditions exist that create undue risk to the mother, the fetus, or both, should the pregnancy continue, and a clinical decision is made to expedite delivery. In these situations, the labour may be induced or the delivery achieved by caesarean section.

• The most common diagnoses that precede an indicated preterm birth are pre-eclampsia, fetal distress, intrauterine growth restriction, placental abruption and fetal demise.

Prevention of preterm labour

Many interventions aimed at reducing the incidence of preterm labour have been implemented and assessed, including:

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