Acute Abdominal Pain in Pregnancy
A pregnant woman who develops this symptom is very likely to be extremely concerned that there is a threat to her pregnancy. Anxiety levels may therefore be high in the patient and her partner. Acknowledge this emotional distress by an urgent and full assessment. Listed here are causes specific to pregnancy and conditions which may be exacerbated or altered by pregnancy; ‘run of the mill’ causes (such as gastroenteritis, IBS and dyspepsia) may obviously occur too, but rarely create diagnostic problems and so are not considered in this section.
Differential diagnosis
Common Diagnoses
- Symphysis Pubis and Ligament Strain
- Miscarriage: 20%–40% of Pregnancies in First Trimester
- Labour: 6% Premature
- Placental Abruption: 1/80–200 Pregnancies
- Pyelonephritis (Especially Around 20 Weeks)
Occasional Diagnoses
- Constipation (Common Cause but Only Occasionally Presents)
- Ectopic Pregnancy (1/250 Pregnancies)
- Appendicitis (1/1000 Pregnancies)
- Red Degeneration of Fibroid
- Torsion/Rupture of Ovarian Cyst or Tumour
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 Strain | Miscarriage | Labour | Abruption | Pyelonephritis | |
|---|---|---|---|---|---|
| Localised Tenderness | Yes | No | No | Possible | Yes |
| Crampy Pain | No | Yes | Yes | No | No |
| Vaginal Bleeding | No | Yes | No | Yes | No |
| Uterine Rigidity | No | No | No | Yes | No |
| Fever, Unilateral Pain | No | No | No | No | Yes |
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
- Distortion of 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.