Acute Abdominal Pain in Pregnancy

Differential Diagnosis

Common Diagnoses

Occasional Diagnoses

Rare Diagnoses

  • Uterine Rupture (in UK 1/1500 Pregnancies, of Which 70% Due to Caesarian Scar Dehiscence)
  • Uterine torsion (Axial Rotation >90°): 90% Associated with Fibroids, Adnexal Masses and Anatomical Uterine Anomalies
  • Liver Congestion Due to Pre-Eclampsia
  • Rectus Sheath Haematoma

Ready Reckoner

Key distinguishing features of the most common diagnoses

S. Pubis StrainMiscarriage LabourAbruptionPyelonephritis
Localised TendernessYesNoNoPossibleYes
Crampy PainNoYesYesNoNo
Vaginal BleedingNoYesNoYesNo
Uterine RigidityNoNoNoYesNo
Fever, Unilateral PainNoNoNoNoYes

Possible Investigations

Likely:Urinalysis, MSU.

Possible:Ultrasound, FBC.

Small Print:Laparoscopy.

  • Urinalysis: Proteinuria in pre-eclampsia. Blood, pus cells and nitrite in urinary tract infection (UTI); the infecting organism will be confirmed on MSU.
  • FBC: Raised WCC in UTI.
  • Imaging ultrasound can be diagnostic in abruption and miscarriage; the presence of an intrauterine pregnancy makes an ectopic very unlikely; ultrasound may also be helpful in detecting a rectus sheath haematoma.
  • Laparoscopy: To confirm ectopic pregnancy.

Top Tips

  • Pain on standing and walking, and relieved by rest, with exquisite pubic symphysis tenderness, is ‘symphyseal pain’ – an often overlooked cause.
  • Allay understandable anxieties as appropriate – particularly regarding the well-being of the foetus or the possibility of premature labour
  • Do not be too ready to diagnose UTI on the basis of an abnormal urinalysis – contamination in pregnancy is common.

Red Flags

  • Changes in anatomy may alter symptoms and signs – appendicitis is notoriously difficult to diagnose in the second trimester. If in doubt, admit.
  • A woman in early pregnancy who experiences unilateral lower abdominal pain followed by light bleeding or blackish discharge has an ectopic until proved otherwise.
  • Don’t overlook the diagnosis of premature labour. Women with no previous experience of labour pain might not consider this possibility.
  • Placental abruption causes severe, continuous pain with a tender, hard uterus. Vaginal bleeding may be minimal. Admit immediately.
  • Don’t forget pre-eclampsia as a cause of epigastric pain in the third trimester – check the blood pressure (BP) and urine.

Published: 1st August 2022 Updated: 3rd April 2024

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