Instrumental Delivery (Operative Vaginal Delivery)

Knowledge Check

Exam-style MCQs aligned with these notes. Available to Hyperexcision Scholar members.

Last updated: April 25, 2025Bookmark

Table Of Contents

Instrumental Delivery
Prerequisites for Instrumental Delivery (Safety Criteria)
Vacuum (Ventouse) Delvery
Forceps Delivery
Complications of Instrumental Delivery

Instrumental Delivery

Instrumental delivery, AKA operative vaginal delivery, refers to the use of suction cups or forceps to assist vaginal delivery in the second stage of labour. The procedure is carried out by an experienced obstetrician with facilities for caesarean delivery available in case instrumental delivery fails.

Classification of instrumental delivery

Classification	Description
Mid	Fetal head at station 0
Low	Leading point of the skull is at station +2 or more but not on the pelvic floor
Outlet	Fetal scalp is visible without separating the labia, has reached the pelvic floor or rotation does not exceed 45 degrees (in ROA or LOA position)

Indications for instrumental delivery
- Failure to progress in the second stage of labour
  - Nulliparous women with lack of progress for 3 hours with regional anaesthesia or 2 hours without regional anaesthesia
  - Multiparous women with lack of progress for 2 hours with regional anaesthesia or 1 hour without regional anaesthesia
- Maternal exhaustion +/ vomiting and distress
- Medical contraindications to bearing down e.g. cardiac disease, myasthenia gravis
- Fetal distress

Prerequisites for Instrumental Delivery (Safety Criteria)

Abdominal exam
- Head is < 1/5 palpable on abdominal exam (commonly 0/5 palpable)
Vaginal exam
- Cervix is fully dilated and membranes have ruptured
- Station is at the level of the ischial spines or below (0/+1/+2/+3)
- Less than moderate caput and moulding
- Adequate pelvix
Preparation
- Clear explanation and informed consent
- Pudendal block (for mid-pelvis rotational delivery)
- Perineal block (for low-pelvic or outlet delivery)
- Empty the bladder and remove foley catheter (or deflate the balloon)
- Episiotomy (routine episiotomy is does not reduce the risk fo severe perineal tearing)
- Aseptic technique
- Prepare theatre staff in-case forceps delivery fails
- Inform paediatrics for neonatal resuscitation
- Anticipate for shoulder dystocia, perineal trauma, and post-partum hemorrhage

Vacuum (Ventouse) Delvery

Ventouse delivery is preferred as first-line delivery by maby obstetricians. It is performed by placing the suction cup on the flexion point (located on the vertex) and applying traction with uterine contractions.

Complications of ventouse delivery
- Failure to achieve vaginal delivery
- Cephalohematoma
- Retinal hemorrhage

Forceps Delivery

Forceps consist of paired blades with shanks joined to gether at a lock, with handles that provide a point for traction. Rotational forceps e.g. Kielland forceps can be used to correct malpositioning while conventional forceps can be used for traction in occiput-anterior positions.

Complications of Instrumental Delivery

Maternal complications of instrumental deliver
- Postpartum hemorrhage
- Episiotomy
- Perineal lacerations
- Fecal and flatus incontinence from injury ot the anal sphincter
- Bladder injury with urinary incontinence
- Injury to the femoral and obturator nerve (resolves in 6 – 8 weeks).
Fetal complications of instrumental delivery
- Cephalohematoma from suction
- Facial nerve palsy with forceps
- Subgaleal hemorrhage
- Intraventricular hemorrhage
- Skull fracture
- Spinal cord injury

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

Calculator ›

Instrumental Delivery

Prerequisites for Instrumental Delivery (Safety Criteria)

Vacuum (Ventouse) Delvery

Forceps Delivery

Complications of Instrumental Delivery

Leave a ReplyCancel Reply