Lower Abdominal Pain + PV Bleeding: Obstetric Approach & Differential Diagnosis

STEP 1 - Immediate Stabilization (Any Gestation)

• 2 large-bore IV cannulas - start crystalloids
• Send bloods: FBC, blood group & cross-match (4-6 units), coagulation screen (PT, aPTT, fibrinogen), urea & electrolytes, LFTs, Kleihauer-Betke (if Rh-negative mother)
• Anti-D immunoglobulin if mother is Rh-negative
• Catheterise - monitor urine output
• Call obstetric senior + anaesthesia early
• Do NOT do digital vaginal examination until placenta praevia is excluded

STEP 2 - History (Key Discriminators)

STEP 3 - Examination

• General: Pallor, tachycardia, hypotension (= haemorrhagic shock)
• Abdomen: Fundal height, uterine tenderness, rigidity ("woody hard" = abruption), fetal lie/presentation
• Speculum examination (before digital): see cervical os - open/closed, products at os, active bleeding site
• Digital VE: Only after placenta praevia excluded on ultrasound

STEP 4 - Investigations

• Bedside USS: Placental location, fetal viability, liquor volume, gestational age
• CTG/Cardiotocograph: Fetal heart rate - look for decelerations, late decelerations, sinusoidal pattern
• Urine hCG if gestation uncertain
• Serum beta-hCG: If ectopic suspected (serial quantitative hCG)
• Coags: DIC screen in abruption
• Kleihauer-Betke test: Quantify feto-maternal haemorrhage

STEP 5 - Differential Diagnosis (Structured by Trimester)

A. FIRST TRIMESTER (< 12 weeks)

1. Ectopic Pregnancy (life-threatening - #1 priority)

• Reason: Implantation outside uterus (90%+ in fallopian tube). As the gestational sac grows, it stretches and then ruptures the tube, causing acute intra-abdominal haemorrhage.
• Pain: Unilateral sharp/stabbing lower abdominal pain, referred shoulder-tip pain (diaphragmatic irritation by blood)
• Bleeding: Scanty, dark PV bleeding (from decidua shedding)
• Signs: Adnexal tenderness, cervical excitation on VE, peritonism if ruptured
• Investigation: Serum beta-hCG positive, USS shows empty uterus + adnexal mass / free fluid in pouch of Douglas
• Risk factors: Previous PID, tubal surgery, IUCD, previous ectopic

2. Threatened Abortion

• Reason: Partial separation of the gestational sac causes PV bleeding; uterus contracts in response producing cramps. Os remains closed.
• Pain: Mild, period-like cramps
• Bleeding: Variable, often painless initially
• Signs: Closed cervical os, uterus size = dates, fetal heart present on USS
• Outcome: 50% proceed to complete miscarriage, 50% continue to viable pregnancy

3. Inevitable / Incomplete Abortion

• Reason: Cervical os dilates, products of conception (POC) begin to pass. Incomplete = some POC remain, causing continued bleeding and uterine cramping.
• Pain: Severe crampy pain (like strong menstrual cramps)
• Bleeding: Heavy, with clots and/or tissue passage
• Signs: Open cervical os, soft uterus, products may be seen at os
• Management: Surgical (ERPC/MVA) or medical (misoprostol)

4. Complete Abortion

• All POC passed. Uterus contracts down. Bleeding and pain settle.
• Signs: Closed os, smaller uterus, hCG falling

5. Septic Abortion

• Reason: Infection of retained POC (spontaneous or post-induced). Endometritis spreads to myometrium.
• Pain: Lower abdominal pain + fever, offensive PV discharge
• Signs: Pyrexia, tender uterus, open os, purulent discharge
• Management: IV antibiotics + urgent evacuation

6. Molar Pregnancy (Hydatidiform Mole)

• Reason: Abnormal trophoblastic proliferation. Vesicular villi cause uterine overdistension; may bleed when villi separate from uterine wall.
• Pain: Mild abdominal pain / hyperemesis
• Bleeding: PV bleeding, "grape-like" vesicles may be passed
• Signs: Uterus large for dates, no fetal heart, "snowstorm" appearance on USS, markedly elevated beta-hCG
• Serious complication: Malignant transformation (choriocarcinoma)

B. SECOND TRIMESTER (13-28 weeks)

7. Mid-Trimester Miscarriage / Cervical Incompetence

• Reason: Weakness of the internal os leads to painless cervical dilation without contractions - "silent" cervical incompetence. Once dilated, membranes prolapse and rupture causing cramping and bleeding.
• Pain: Pressure/heaviness, then cramps
• Bleeding: Variable
• Signs: Dilated os, bulging membranes; history of mid-trimester losses
• Management: Emergency cervical cerclage if cervix < 3 cm dilated

8. Placental Abruption (can occur from 20 weeks onward)

9. Uterine Fibroids (Red Degeneration)

• Reason: Rapid growth of fibroids in pregnancy (due to oestrogen/progesterone stimulus) outstrips blood supply, causing central necrosis (red/carneous degeneration).
• Pain: Localised, constant, severe tenderness directly over fibroid
• Bleeding: PV bleeding (from submucosal fibroids)
• Management: Analgesia (NSAIDs), conservative; spontaneous resolution over days

C. THIRD TRIMESTER / ANTEPARTUM HAEMORRHAGE (APH) - After 28 weeks

10. Placenta Praevia (most important painless cause)

• Reason: Placenta implants in the lower uterine segment (LUS). As the LUS forms and cervix effaces in late pregnancy, the placental attachment tears away from the uterine wall causing haemorrhage.
• Pain: Painless - this is the hallmark
• Bleeding: Sudden, painless, bright red PV bleeding - can be torrential; tends to recur
• Signs: Soft non-tender uterus, fetal malpresentation (transverse/oblique lie) is common because the low placenta prevents engagement, presenting part high
• USS: Placenta over/near internal os
• NEVER do digital VE - can precipitate catastrophic haemorrhage
• Grades: I (lateral), II (marginal), III (partial), IV (central/complete)

11. Placental Abruption (most important painful cause)

• Reason: Premature separation of normally sited placenta from the uterine wall. Blood accumulates between placenta and uterine wall (retroplacental clot), causing severe pain and myometrial irritation. Extensive abruption can cause DIC (release of thromboplastins into maternal circulation).
• Pain: Sudden, severe, constant lower abdominal pain - knife-like or "tearing". Does NOT wane between contractions (unlike normal labour).
• Bleeding: PV bleeding (may be minimal if blood is concealed behind placenta). The amount of PV bleeding does NOT reflect the actual blood loss.
• Signs: Uterus "woody hard" / board-like, extreme tenderness, uterus may be larger than dates (concealed haemorrhage), absent fetal heart sounds (fetal distress/death)
• Complications: DIC, renal failure, Couvelaire uterus, fetal death
• Risk factors: Hypertension/pre-eclampsia, trauma, smoking, cocaine, multiparity, short umbilical cord

12. Vasa Praevia

• Reason: Fetal blood vessels run in the membranes across the internal os (velamentous cord insertion). When membranes rupture (SROM or ARM), these fetal vessels tear.
• Pain: Mild abdominal pain
• Bleeding: PV bleeding at the time of membrane rupture - fetal blood (not maternal). Rapid fetal exsanguination - fetal mortality 60-75% if unrecognised.
• Signs: Sinusoidal fetal heart trace; Apt test / Kleihauer test confirms fetal blood in vaginal bleeding
• Management: Emergency caesarean section

13. Uterine Rupture (can occur in labour or late pregnancy)

• Reason: Scar dehiscence (previous LSCS, myomectomy) or spontaneous rupture (obstructed labour, oxytocin hyperstimulation). Full-thickness tear of uterine wall allows fetus to partially or fully enter peritoneal cavity.
• Pain: Sudden excruciating abdominal pain, often preceded by scar pain. "Tearing" sensation.
• Bleeding: PV bleeding + intra-abdominal haemorrhage (may not correlate)
• Signs: Sudden cessation of contractions, fetal parts palpable superficially, fetal bradycardia/absent FHR, haemodynamic shock, loss of previously engaged presenting part
• Management: Emergency laparotomy

14. Show / Bloody Show (Normal)

• Reason: Expulsion of cervical mucous plug + capillary blood as cervix effaces and dilates in early labour
• Pain: Mild lower abdominal cramping (early contractions)
• Bleeding: Bloodstained mucous, scant
• Signs: Regular contractions, cervix effaced/dilating
• Diagnosis of exclusion - exclude pathology first

15. Chorioamnionitis

• Reason: Ascending bacterial infection of membranes/amniotic fluid. Causes uterine irritability, contractions, and PV bleeding.
• Pain: Lower abdominal pain + uterine tenderness
• Fever: Always present; maternal tachycardia, fetal tachycardia
• Bleeding: Variable
• Signs: Offensive liquor if membranes ruptured, elevated WCC/CRP

SUMMARY TABLE: Key Distinguishing Features

MANAGEMENT PRINCIPLES

Haemodynamically Unstable

1. Resuscitate: 2 x IV access, fluids, blood products (FFP, platelets if DIC)
2. Call obstetric consultant + anaesthetist + theatre NOW
3. If fetus viable and distressed - emergency LSCS
4. If ectopic ruptured - emergency laparotomy / laparoscopy

Haemodynamically Stable

1. Monitor with CTG
2. USS (transabdominal + transvaginal) to localise placenta, assess fetal wellbeing
3. Serial beta-hCG if ectopic suspected
4. Corticosteroids (betamethasone 12 mg IM x 2 doses) if preterm (< 34+6 weeks) and delivery anticipated
5. Tocolysis if preterm labour (after abruption excluded)
6. Magnesium sulphate neuroprotection if < 32 weeks

Anti-D

• Give anti-D immunoglobulin 300 mcg IM to all Rh-negative women with APH within 72 hours