CHAPTER 12 Preterm labour is defined as labour occurring more than 3 weeks before the expected date of delivery – that is, before the completion of 37 weeks of pregnancy. Preterm labour is a significant predictor of neonatal morbidity and mortality. The survival of newborns delivered before the 24th week of pregnancy is unusual, although not impossible. In 2013, 66% of babies born between 24 and 27 weeks’ gestation survived the first 28 days of life, increasing to 89% between 28 and 31 weeks’ gestation and 98% at 32–36 weeks’ gestation (MBRRACE‐UK, 2015b). The signs and symptoms may be similar to that of normal labour, although there may be little or no contraction pain and the membranes may rupture before the onset of labour. Malpresentations – such as breech presentation – are common. It is unlikely that the head has engaged before labour starts, and if the membranes have ruptured, the practitioner should be aware of the possibility of cord prolapse. The relationship of the baby to the mother is important in labour. The following definitions help to describe them. Lie – refers to the relationship of the long axis of the baby to that of the mother. These are longitudinal, transverse or oblique (Figure 12.1). If the lie changes it may be referred to as unstable. Presentation – refers to the part of the baby that is presenting or foremost in the birth canal. The baby can present with its head (also known as cephalic presentation), breech (buttocks, feet or legs), face, brow or shoulder (Figure 12.2). Position – refers to a reference point on the presenting part, and how it relates to the maternal pelvis. For example, the most common position is the occipitoanterior position (OA position). This occurs when the fetal occiput is directed towards the maternal symphysis or anteriorly (Figure 12.3). However, a common malposition is the occipitoposterior position (OP position). This occurs when the occiput is directed towards the maternal spine (ALSO, 2004). Breech presentation is a longitudinal lie with the fetal buttocks presenting in the birth canal, with the after‐coming head in the uterine fundus (Boyle, 2002; ALSO, 2004). The incidence is approximately 20% at 28 weeks. However, as most babies turn spontaneously, the incidence at term is 3–4% (Impey et al., 2017a). Breech presentations are associated with a higher perinatal mortality and morbidity rate, due principally to premature births, congenital malformations and birth asphyxia and trauma (Pritchard and MacDonald, 1980; Cheng and Hannah, 1993). The Term Breech Trial suggested that delivery by caesarean section is safer, with a lower newborn morbidity, for term pregnancies not yet in labour (Hannah, 2000). As first‐line management, women diagnosed antenatally with a breech presentation at term should first be offered an external cephalic manipulation (an obstetric practitioner turning the fetus by hand) (Impey et al., 2017b). Although the management of breech presentations has changed, there will still always be vaginal breech deliveries. These will occur as a result of undiagnosed breeches, rapid deliveries and patient choice. Therefore, all maternity care providers should be prepared for spontaneous breech deliveries. Breech presentations can be classified as in Table 12.1. Table 12.1 Classification of breech presentations The signs and symptoms will be similar to those of labour with a cephalic presentation. However, on inspection of the introitus, the following may be visible:
Complicated labour and delivery
12.1 Preterm labour
Definition
Risk factors
Diagnosis
Pre‐hospital management
12.2 Abnormal presentations and lies
Definition
12.3 Breech presentation
Definition
Type of breech presentation
Hips
Legs
Feet
Proportion of breech presentations
Frank (extended) breech
Flexed
Extended
65%
Complete (flexed) breech
Flexed
Flexed
25%
Footling breech
One or both extended
One or both extended
One or both presenting
10%
Risk factors
Diagnosis
Pre‐hospital management