**Abstract**

Preterm delivery is defined as delivery before 37 weeks completed gestation. It represents a major cause of neonatal morbidity and mortality and accounts for 5–10% of all deliveries. Cervical length assessment between 16–24 weeks and positive fetal fibronectin beyond 21 weeks gestation are proved to useful tools in prediction of preterm labour. Treating asymptomatic bacteruia and bacterial vaginosis in high-risk women reduces the incidence of preterm labour. Cervical cerclage is recommended to reduce the incidence of preterm birth in women with 2nd trimester losses and those with cervical length of 25 mm or less on transvaginal ultrasound between 16–24 weks gestation. Atosiban and nifidipine are currently the agents of choice in tocolysis. Antenal steriods in womens with threating preterm labour reduces the perinatal morbidties. Magnisum sulphate role is established for neuroprotection especially in extreme gestations between 24–30 weeks. Vaginal delivery is mode of choice for delivery with consideration to avoid fetal blood sampling, fetal scalp electrodes and ventouse prior to 34 weeks gestations. Caesarean section is considered for obstetric reasons that guide labour management at term.

**Keywords:** definition, maternal morbidity, feral morbidity, risk factors, tocolysis, antenatal steroids

#### **1. Introduction**

Preterm delivery is defined as delivery before 37 weeks completed gestation. It represents a major cause of neonatal morbidity and mortality in both developed and developing countries with European and North American figures ranges between 5–10% of all deliveries. In the UK it represents 7.3% of live births

Extreme preterm birth is defined as preterm birth prior to 28 weeks gestation. It accounts for 5–10% of preterm deliveries. The major concern of extreme preterm birth is the significant risk of neonatal mortality as the survival rates are very low at these gestations (0.4% at 22 weeks, 7% at 24 weeks) while the main concern of preterm births above 28 weeks is the neonatal morbidity as the survival rates are 77% at 28 weeks and 97% at 36 weeks.

## **2. Aetiology**

The aetiology of preterm labour is multifactorial with a common pathway resluting in increased relasee of prostaglandins and cytokines within the cervix, myometrium and fetal membranes. The release of prostaglandins is triggered by infective or inflammatory process [1], uterine overdistension as in cases with polyhydraminons and mutiple preganacy or choriodecudidual haemorrhage as in cases with abruption.

In modern obstetrics, 30–40% of preterm deliveries are iatrogenic. The most common cause of which is severe pre-eclampsia associated with intrauterine growth restriction (IUGR) and antenatal fetal distress. Other common iatrogenic preterm deliveries include, Grade 3 and 4 placenta praevia or placenta abruption with major bleeding, sever IUGR with absent or reversed end-diastolic flow. It is also notable that the increased number of large loop excision of transformation zone (LLETZ) procedures for abnormal cervical cells leads to cervical scarring and iatrogenic cervical incompetence and hence preterm delivery.

### **3. Prediction of preterm labour**

Identifying high risk patients is crucial in managing and preventing preterm labour. Prediction of preterm labour is possble through; risk assessment, uterine activity monitoring, cervical length assessment and fetal fibronectin assessment.

#### **3.1 History taking and risk assessment**

Patients with previous preterm labour are at higher risk of having pretem term birth. The risk is 17% after one previous preterm delivery and increases to 28% after two preterm deliveries. Patients with previous preterm premature rupture of membranes (PROM) [2], previous second trimester loss and thoese who are known to have cervical incomptence and congenital uterine anaomalies are at higher risk for preterm birth. Fruther more uterine overdistention as with Polyhydraminos and mutiple pregnancy is associated with preterm delivery. Patient with placental abruption are also known to be at higher risk of preterm labour.

**Scoring systems were developed in attempts to achieve accurate and numerical score to help the management of preterm labour. However; the scoring systems proved to have poor sensitivity and poor postive predictive values as more that 50% of preterm labour occurs in the first pregnancy and in womens with no risk factors** [3]**.**

#### **3.2 Monitoring uterine activity**

It notable that uterine activity increases prior to onset of pretrm labour by 24 hours. However, the use of home uterine contraction monitors or self palpations has not proven to be useful as they had poor postive predictive vlaues and their use did not improve the perinatal outcomes.

#### **3.3 Assessment of cervical length**

Clinical assessment of cervical status in terms of dilatation, softening and effacement can predict preterm labour, However it has low sensitivity and repeated vaginal examination in it self may incease the cervical prostaglandins relase and subsquently increase the incidnce of preterm labour.

Utrasound assessment of cervical length is a reliable method and highest predictive value up to 70% is notable with cervical length under 25 mm in womens with risk factors for preterm labour. Serial cervical length assessment is recommended in hight isk group between 16–24 weeks. Cervical length is best measured by transvaginal scan with empty bladder as full bladder may lead to false increase in the cervical length measurments. The risk of preterm labour increases from 1% at cervical length of 25 mm to 4% at 15 mm cervical length. The marked increased risk is notable at 5 mm cervical length with preterm birth risk of 78% [4, 5].

#### *Preterm Labour DOI: http://dx.doi.org/10.5772/intechopen.96049*

Cervical length assessment is not routine in womens with no risk factors for preterm birth as the positive predictive value is low in this group. Also, preventive interventions as cervical cerclage is not recommended in low risk group as they have shown no improvement in the outcome in this group [4].

The presence of funnelling of the internal os is another helpful finding in predicting the preterm birth, However, it is less accurate compared to cervical length assessment due to inter and intra observer variations [6].

#### **3.4 Fetal fibronectin testing**

Fetal fibronectin is normally present in high concentration prior to 21 weeks of gestation in cervical and vaginal secretions prior to membranes fusion. Inflammatory process, uterine overdistension and choriodecidual haemorrhage increase fetal fibronectin secretion after 21 weeks gestation.

Fetal fibronectin testing by swabbing the posterior fornix or ectocervix between 22 and 34 weeks gestation in recommended as postive results in high risk group especially in presence of symptoms warrant admistration of steriods and hospital admission. Fetal fibronectin testing is not recommeded in womens with no risk factors as it has not shown to be effective in improving the outcome despite more than half of preterm birth occurs in this group [7].

Testing for fetal fibronectin is contraindicated before 22 weeks gestation, in presence of preterm premature rupture of membranes, active vaginal bleeding and intercourse in the previous 24 hours.

Other biochemical markers such as Insulin like growth factor binding protein-1, interleukin-6, interleukin-8 and tumour necrosis factor-alpha (TNF-α) were assessed in research setting for use in predicting preterm labour. However, none of those markers is currently used in routine practice [8].

## **4. Neonatal morbidity and mortality of preterm labour**

Preterm birth is associated with significant neonatal morbidities such as respiratory distress syndrome, necrotizing enterocolitis, retinopathy of prematurity, neonatal sepsis, intraventricular haemorrhage and periventricular leucomalacia. Longterm impact of prematurity are mainly cognitive and motor impairement which are more prevelant in extreme preterm births. Prolongation of pregnancy with tocolytic agents and adminstration of antenatal steriods signficantly reduces the neonatal morbidities in preterm births [1, 9].

EPICure data [9] may be useful tool in counselling the parents about fetal prognosis. Neonatal mortality is higher with preterm birth at lower gestational ages with survival rate of 7% at 24 weeks compared to 77% at 28 weeks and 97% at 32 weeks. The survival rates improves 2.2% daily between 24 and 28 weeks gestions. Preterm delivery at 36 weeks is associated with 99% survival rate [1, 9, 10].

#### **5. Prevention of preterm delivery**

Mutiple preventive measures were tested for prevention of preterm labour such as treatment of asymptomatic bacteruria and bacterial vaginosis, prophylactic antibiotics in womens with postive fetal fibronectin and reduced cervical length, cervical cerclage, prophlactic tocolysis and hormonal supplements. Some were proved to be effective in reducing preterm deliveries while others shown no significant diffierence in the outcome regarding the incidance of preterm birth and its associated morbidities.

