Latent Phase Disorder

Latent phase disorder is an abnormality of the early part of labour, from the onset of regular painful contractions until the cervix reaches 5 cm, in which contractions do not produce progressive cervical change. It includes false labour and prolonged latent phase. Causes are an unripe cervix, malposition, early sedation or epidural, anxiety, dehydration and genuine slow start. It matters because mistaking it for dysfunctional active labour leads to unnecessary caesarean section.

• Risk factors: first pregnancy, unfavourable cervix, occiput posterior position, obesity, premature admission, early epidural.
• Most progress after rest and hydration.
• Caesarean section is not done for latent phase slowness alone.

Women have painful contractions that are irregular or regular, with little or no cervical change over hours, and become tired and distressed. The cervix is soft or firm, 0 to 4 cm dilated.

• Cervix changing by less than 1 cm over 4 hours.
• Contractions may stop (false labour).
• Differential diagnosis: false labour, true early labour, urinary infection, chorioamnionitis, abruption, fetal malposition, uterine fibroid obstruction.
• Complications: exhaustion, dehydration, unnecessary admission and intervention, prolonged labour, infection if membranes are ruptured, caesarean section.

The approach is repeated assessment of contractions and cervix over 4 hours.

• Record contraction frequency and duration; digital cervical examination at 4 hour intervals (earlier if indicated) to document dilatation, effacement, station and position; membrane status.
• Cardiotocography for 20 to 30 minutes; urine dipstick for ketones and infection.
• Temperature, pulse, blood pressure, hydration.
• Ultrasound for fetal position if malposition is suspected.

The principle is rest, fluids and analgesia, with oxytocin only if the latent phase is prolonged and the pregnancy is safe to hasten.

• Supportive: hydration (oral fluids or Ringer's lactate 1 litre IV over 2 hours); walking, bath or warm shower; empty bladder; supportive companion; rest and sleep; discharge home if membranes are intact and fetal wellbeing is normal, with warning signs; admit for ruptured membranes, abnormal tracing or distress.
• Pharmacological: paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours); morphine 10 mg IM plus promethazine 25 mg IM for therapeutic rest (6 to 12 hours of sleep); oxytocin starting at 2 mU/minute and doubling every 30 minutes to a maximum of 32 mU/minute if ruptured membranes with no progress after 8 hours or a prolonged latent phase; 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; cefazolin 2 g IV before caesarean section.
• Procedures: amniotomy when the head is engaged and the cervix is 3 cm or more dilated; caesarean section only for obstetric indications.
• Special groups: women with a previous caesarean section avoid misoprostol and use oxytocin with senior review; grand multiparas have oxytocin with caution because of the risk of uterine rupture.
• Red flags: fever above 38 degrees Celsius, abnormal fetal heart rate, bleeding, thick meconium, severe pain between contractions, ruptured membranes for 18 hours or more.
• Follow-up: reassess cervix at 4 hours; if still latent after 8 hours, review the plan; maternal temperature 4-hourly if membranes are ruptured; routine postnatal care.