Prolonged Latent Phase

Prolonged latent phase is a latent phase of labour that lasts more than 20 hours in a first labour or more than 14 hours in a later labour. It results from an unripe cervix, malposition, excessive sedation or early epidural, hypotonic contractions and anxiety. It matters because exhaustion, infection and intervention follow, though most women go on to a normal vaginal birth.

• Risk factors: first pregnancy, unfavourable cervix, occiput posterior position, obesity, advanced age, sedation, early epidural.
• Abnormal latent phase does not predict a problem in active labour.
• Caesarean section is for obstetric indications only.

Women have painful contractions for many hours with a cervix that remains less than 5 cm dilated. They are tired, anxious and dehydrated.

• Contractions every 5 to 10 minutes lasting 30 seconds.
• Little change in dilatation over hours.
• Differential diagnosis: false labour, malposition, cephalopelvic disproportion, chorioamnionitis, urinary infection, abruption, uterine fibroid.
• Complications: exhaustion, dehydration and ketosis, infection if membranes are ruptured, prolonged labour, oxytocin use, caesarean section, postpartum haemorrhage.

The approach is to measure the duration of the latent phase and to exclude other causes.

• Record the time of onset of regular painful contractions; cervical examination at 4 hour intervals; contraction frequency and duration.
• Fetal position by palpation and ultrasound; pelvic assessment; estimated fetal weight.
• Temperature, pulse, hydration, urine ketones; cardiotocography.
• Full blood count and C-reactive protein if rupture of membranes exceeds 18 hours or there is fever.

The principle is therapeutic rest followed by amniotomy or oxytocin if labour does not start.

• Supportive: hydration (Ringer's lactate 1 litre IV over 2 hours); warm bath, walking or rest; empty bladder; supportive companion; admit for ruptured membranes or abnormal tracing; avoid early epidural.
• Pharmacological: morphine 10 mg IM plus promethazine 25 mg IM (or pethidine 100 mg IM plus promethazine 25 mg IM) for therapeutic rest, expecting 6 to 12 hours of sleep; most enter active labour after rest, some stop contracting and a few remain in latent phase; oxytocin starting at 2 mU/minute and doubling every 30 minutes to a maximum of 32 mU/minute for women who remain in latent phase or after the rest period, aiming for 3 to 4 contractions in 10 minutes lasting 40 to 60 seconds; benzylpenicillin 5 million units IV then 2.5 million units 4-hourly in labour for group B streptococcus or rupture for 18 hours or more; ampicillin 2 g IV 6-hourly plus gentamicin 5 mg/kg IV once daily for chorioamnionitis; paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours).
• Procedures: amniotomy when the cervix is 3 cm or more dilated and the head is engaged; Foley catheter with a 30 mL balloon for ripening; caesarean section only for fetal compromise, cephalopelvic disproportion or failed induction after 24 hours of oxytocin with ruptured membranes.
• Special groups: previous caesarean section avoids misoprostol and uses oxytocin with senior review; grand multiparas have oxytocin with caution because of the risk of uterine rupture; sedation is avoided close to birth because of neonatal respiratory depression.
• Red flags: fever above 38 degrees Celsius, abnormal fetal heart rate, bleeding, thick meconium, ruptured membranes for 18 hours or more, severe pain between contractions.
• Follow-up: reassess cervix 4-hourly; temperature 4-hourly if membranes are ruptured; newborn observation if maternal opioids were given within 4 hours of birth.