Abnormal Labour and Delivery

Last updated: November 13, 2024

Table Of Contents

Overview
- The Montevideo Unit
Protraction disorders
Arrest disorders
- Arrested active phase

Overview

Approximately 20% of labour involves dystocia. Labour abnormalities can be classified as disorders of protraction and disorders of arrest. .Remember that Labour is defined as regular contractions (every 5 minutes lasting ~ 30 secs.) accompanied by cervical dilation and effacement leading to descent and expulsion of the fetus. Abnormal labour is the result of one or more abnormalities of the cervix, uterus, maternal pelvis, or fetus (power, passenger, or pelvis)

Expected values

	Event	Primipara	Multipara
Latent stage one	closed to 4 cm dilation	< 20 hours	< 14 hours
Active stage one	4 cm to full dilation	< 5-6 hours	< 4-5 hours
Rate of cervical dilation	acceleration of dilation in active stage one	1.0 – 1.2 cm/hr	1.2 – 1.5 cm/hr
Stage two	full dilation	< 2 hours	< 1 hour
Stage three	two hours following	30 min	30 min

The Montevideo Unit

200 MVU over 10 minutes is needed for labour to progress properly. Lower than 200 MVU suggests prolongation or arrest of labour.

Montevideo units = [Peak pressure per contraction (mmHg) – resting tone of the uterus (mmHg)] X Frequency of contractions (in 10 minutes)

A patient has 5 contractions in 1- minute, each with a peak pressure of 70 mmHg. The resting tone is 13 mmHg. How many Montevideo units are these?
- Has 285 MVU

Protraction disorders

Prolonged latent phase

The patient is in labour and remains < 3 cm dilated for > 20 hrs (primip) or > 14 hrs (multip)

Causes
- Anesthesia (spinal) administered too early
- Irregular contractions
  - Hypotonic (infrequent, weak contractions)
  - Hypertonic (strong, short contrations)
Differential
- False labour: cervix of a nullipara is long and closed, or just admitting a finger tip. The cervix of a multipara is not effaced (even if dilated).
Treatment
- Rest (Let her sleep)
- Morphine sedation
  - Contractions stop after administration in False labour (10%)
  - Otherwise, cervical changes will have occurred by the time sedation wears off in True labor (90%)
- Amniotomy in the case of pre-eclampsia, gestational diabetes and sickle cell

Prolonged active phase

The patient is in labour and remains <1.2 cm/hr (primipara) or < 1.5 cm/hr (multipara) Causes are the 3Ps. Treatment relies on the tonicity of the contractions

Passenger causes
- Obstructed labour due to
  - Increased fetal size
  - Abnormal orientation in utero (breech, transverse lie, etc.)
Pelvic causes
- Cephalopelvic disproportion (If Hx of CPD with similar or smaller babies then it is probably the case. If no CPD with larger babies CPD is unlikely – can feel the promontory when measuring diagonal conjugate, head 4/5 above the brim, marked moulding)
Power causes
- Dysfunctional or inadequate contractions
Treatment
- Hypotonic contractions: IV Oxytocin
- Hypertonic contractions: Morphine sedation. Can administer Terbutaline.
- Eutonic contractions: Emergent Caeserean

Prolonged second stage

The patient is 10 cm dilated *and *fails to deliver the infant in ≤ 2 hrs (primip) or ≤ 1 hr (multip) [add one hour if the patient has received spinal anaesthesia]. Causes are also 3Ps. Good contractions are 3-4 in 10 minutes each lasting >40 seconds. No oxytocin for augmentation of labour in multipara unless you supervise it personally. Certainly not oxytocin for multipara >5, and not for longer than 2 hours. A multipara not steadily progressing in the second stage of labour and has started to push but has not delivered in 60 minutes is in great danger of uterine rupture.

Passenger causes
- Increased fetal seize
- Persistent OT position
- Abnormal presentation (e.g. breech)
- Asynclitism
Treatment
- Assess contractions
- Correct dehydration and ketosis by IV RL or NS
- Analgesia using Epidural or Pethidine 100mg + Promethazine 25mg IM
- Inadequate contractions → IV Oxytocin 5U in 500ml D5 to augment labor
- Adequate contractions → assess the engagement of the fetal head (if fully dilated you have access to the fetus)
  - Engaged → Consider forceps or vacuum delivery attempt
  - Not engaged (significant CPD)→ Emergent caesarean
Indications for C-section in prolonged second stage
- Gross CPD
- Fetal distress
- Malpresentation

Prolonged third stage

Failure to deliver the placenta in ≤ 30 minutes

Causes
- Inadequate contractions
- Abnormal placentation (accreta, increta, percreta)

Arrest disorders

Arrested active phase

The patient is in labour and has no cervical change for 2-3 hours. Tx is the same as the prolonged active phase.

Treatment
- Assess contractions
  - Inadequate → IV Oxytocin (usually given as prophylaxis)
  - Adequate → Attempt manual removal; rarely hysterectomy

Reference Intervals ›

Biochemistry

ACTH	P: <80 ng/L
ALT	P: 5–35 U/L
Albumin	P: 35–50 g/L
Aldosterone	P: 100–500 pmol/L
Alk. phosphatase	P: 30–130 U/L
α-Amylase	P: 0–180 IU/dL
α-Fetoprotein	S: <10 kU/L
Angiotensin II	P: 5–35 pmol/L
ADH	P: 0.9–4.6 pmol/L
AST	P: 5–35 U/L
Bicarbonate	P: 24–30 mmol/L
Bilirubin	P: 3–17 μmol/L
BNP	P: <50 ng/L
CRP	P: <10 mg/L
Calcitonin	P: <0.1 mcg/L
Calcium (ionized)	P: 1.0–1.25 mmol/L
Calcium (total)	P: 2.12–2.60 mmol/L
Chloride	P: 95–105 mmol/L
Cholesterol	P: <5.0 mmol/L
VLDL	P: 0.128–0.645 mmol/L
LDL	P: <2.0 mmol/L
HDL	P: 0.9–1.93 mmol/L
Cortisol AM	P: 450–700 nmol/L
Cortisol Midnight	P: 80–280 nmol/L
CK ♂	P: 25–195 U/L
CK ♀	P: 25–170 U/L
Creatinine	P: 70–100 μmol/L
Ferritin	P: 12–200 mcg/L
Folate	S: 2.1 mcg/L
FSH	P: 2–8 U/L ♂; >25 menopause
GGT ♂	P: 11–51 U/L
GGT ♀	P: 7–33 U/L
Glucose (fasting)	P: 3.5–5.5 mmol/L
Growth hormone	P: <20 mu/L
HbA1C (DCCT)	B: 4–6%
HbA1C (IFCC)	B: 20–42 mmol/mol
Iron ♂	S: 14–31 μmol/L
Iron ♀	S: 11–30 μmol/L
Lactate (venous)	P: 0.6–2.4 mmol/L
Lactate (arterial)	P: 0.6–1.8 mmol/L
LDH	P: 70–250 U/L
LH	P: 3–16 U/L
Magnesium	P: 0.75–1.05 mmol/L
Osmolality	P: 278–305 mosmol/kg
PTH	P: 0.8–8.5 pmol/L
Potassium	P: 3.5–5.3 mmol/L
Prolactin ♂	P: <450 U/L
Prolactin ♀	P: <600 U/L
PSA	P: 0–4 mcg/mL
Protein (total)	P: 60–80 g/L
Red cell folate	B: 0.36–1.44 μmol/L
Renin (erect)	P: 2.8–4.5 pmol/mL/h
Renin (recumbent)	P: 1.1–2.7 pmol/mL/h
Sodium	P: 135–145 mmol/L
TBG	P: 7–17 mg/L
TSH	P: 0.5–4.2 mU/L
T4	P: 70–140 nmol/L
Free T4	P: 9–22 pmol/L
TIBC	S: 54–75 μmol/L
Triglycerides	P: 0.50–2.3 mmol/L
T3	P: 1.2–3.0 nmol/L
Troponin T	P: <0.1 mcg/L
Urate ♂	P: 210–480 μmol/L
Urate ♀	P: 150–390 μmol/L
Urea	P: 2.5–6.7 mmol/L
Vitamin B12	S: 0.13–0.68 nmol/L
Vitamin D	S: 50 nmol/L

Arterial Blood Gases

pH	7.35–7.45
PaCO₂	4.7–6.0 kPa
PaO₂	>10.6 kPa
Base excess	±2 mmol/L

Urine

Cortisol (free)	<280 nmol/24h
Hydroxyindole acetic acid	16–73 μmol/24h
Hydroxymethylmandelic acid	16–48 μmol/24h
Metanephrines	0.03–0.69 μmol/mmol cr.
Osmolality	350–1000 mosmol/kg
17-Oxogenic steroids ♂	28–30 μmol/24h
17-Oxogenic steroids ♀	21–66 μmol/24h
17-Oxosteroids ♂	17–76 μmol/24h
17-Oxosteroids ♀	14–59 μmol/24h
Phosphate (inorganic)	15–50 mmol/24h
Potassium	14–120 mmol/24h
Protein	<150 mg/24h
Protein/creatinine ratio	<3 mg/mmol
Sodium	100–250 mmol/24h

Haematology

WCC	4.0–11.0 ×10⁹/L
RBC ♂	4.5–6.5 ×10¹²/L
RBC ♀	3.9–5.6 ×10¹²/L
Hb ♂	130–180 g/L
Hb ♀	115–160 g/L
PCV ♂	0.4–0.54 L/L
PCV ♀	0.37–0.47 L/L
MCV	76–96 fL
MCH	27–32 pg
MCHC	300–360 g/L
RDW	11.6–14.6%
Neutrophils	2.0–7.5 ×10⁹/L (40–75%)
Lymphocytes	1.0–4.5 ×10⁹/L (20–45%)
Eosinophils	0.04–0.44 ×10⁹/L (1–6%)
Basophils	0–0.10 ×10⁹/L (0–1%)
Monocytes	0.2–0.8 ×10⁹/L (2–10%)
Platelets	150–400 ×10⁹/L
Reticulocytes	0.8–2.0% / 25–100 ×10⁹/L
Prothrombin time	10–14 s
APTT	35–45 s

Paediatric

Pulse Rate (bpm)
Neonate	140–160
Infant <1yr	120–140
1–5 years	110–130
5–12 years	80–120
>12 years	70–100
Respiratory Rate (tachypnoea)
0–2 months	≥60/min
2–12 months	≥50/min
1–5 years	≥40/min
>5 years	≥30/min
Blood Pressure (mmHg)
Term	65/45
1 year	75/50
4 years	85/60
8 years	95/65
10 years	100/70
Weight Formulas
3–12 months	(a + 9)/2 kg
1–6 years	2a + 8 kg
>6 years	(7a − 5)/2 kg
Haemoglobin (g/dL)
Term newborn	13–20
1 month	11–18
2 months	10–15
1–2 years	10–13
>2 years	11–14
MUAC (6 months–5 years)
Obese	>17.5 cm
Normal	13.5–17.4 cm
At risk	12.5–13.4 cm
Moderate malnutrition	11.5–12.4 cm
Severe malnutrition	<11.5 cm
Developmental Milestones
Social smile	1.5 months
Head control	4 months
Sits unsupported	7 months
Crawls	10 months
Stands unsupported	10–12 months
Walks	12–13 months
Talks	18 months
CSF WBC (/mm³)
Term newborn	0–25
>2 weeks	0–5

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