Abdominal Pain In Pregnancy

Abdominal pain in pregnancy may be difficult to diagnose. Unless a benign cause can be established with certainty in the absence of maternal or fetal distress then urgent hospital referral is usually indicated. Causes unrelated to pregnancy must be considered. Acute conditions such as appendicitis carry higher risks in pregnancy, and may increase the risk of premature labour or fetal loss.¹

This article is written for the primary care or A&E scenario.

This section lists the causes most relevant to pregnancy and women of child-bearing age. For other abdominal pain scenarios see related article Abdominal Pain. Presenting features of note are also discussed here.

'Abdominal' causes¹

• Acute appendicitis - the most common cause of acute abdomen in pregnancy, but more difficult to diagnose because:
  • The classical symptoms/signs are less clear during pregnancy; right lower quadrant pain is the most consistent symptom.
  • The appendix migrates upwards and to the right with uterine enlargement.
  • There may be urinary symptoms and positive urine dipstick results due to pelvic peritonitis, which can confuse the diagnosis.
• Cholecystitis - also common; gallstones enlarge during pregnancy and may present for the first time
• Intestinal obstruction - often due to adhesions from previous surgery
• Peritonitis from any cause
• Peptic ulcer
• Inflammatory bowel disease
• Acute pancreatitis - rare, usually due to gallstones

Renal causes

• Urinary tract infection +/- pyelonephritis - both common in pregnancy
• Renal stones

'Medical' causes

• Pulmonary embolus - an important cause of maternal death
• Diabetic ketoacidosis
• Sickle-cell anaemia crisis
• Others: myocardial infarction, lower lobe pneumonia, malaria, porphyria

Gynaecological causes

• Ectopic pregnancy:⁴
  • Assume ectopic pregnancy until proved otherwise, in any woman of child-bearing age with abdominal pain.
  • Symptoms vary and include: syncope, dysuria (including dipstick urine findings suggesting UTI), diarrhoea & vomiting, subtle changes in vital signs; adnexal tenderness may be absent.
  • History of 'missed period' may be absent if vaginal bleeding is mistaken for a normal period.
• Miscarriage:
  • With incomplete miscarriage, there may be bradycardia and shock if products in os cause vagal stimulation
• Ovarian cysts - torsion, haemorrhage or rupture are more common during pregnancy
• Fibroids - red degeneration or torsion
• Ovarian hyperstimulation syndrome:⁵
  • A complication of gonadotrophin-assisted conception; can occur pre-conception or in early pregnancy
  • Large ovarian cysts cause abdominal pain and distention; in severe cases also fluid shifts, ascites, pleural effusion and shock

Obstetric causes⁶

• Pre-eclampsia or HELLP syndrome:³ - can present with hepatic or epigastric pain
• Placental abruption:⁶
  • Typically, sudden severe pain and a ‘woody’ hard, tender uterus; fetal distress, ± vaginal bleeding
  • With posterior placenta, pain and shock may be less severe, with pain felt in the back; diagnose by pattern of fetal contractions (excessive and frequent) with fetal heart pattern suggesting hypoxia
• Uterine rupture (rare):
  • Constant pain, profound shock, fetal distress and vaginal bleeding; usually presents during labour and with history of uterine scar
  • Rarely, occurs without labour and without uterine scar
• Labour
• Acute polyhydramnios
• Chorioamnionitis:
  • Usually follows premature rupture of membranes, but can occur with membranes intact
• Acute fatty liver of pregnancy:^7,8
  • Not common, but incidence may be higher than previously known⁹
  • Rapid onset abdominal pain, nausea/vomiting, jaundice and headache
  • Electrolytes, liver function and clotting abnormal; requires urgent delivery of fetus and maternal support
• Severe uterine torsion¹⁰ - rare, may be due to structural abnormalities in the pelvis
  • Presents in 2nd half of pregnancy with variable symptoms, including severe abdominal pain, tense uterus, retention of urine ± shock and fetal distress; or may be asymptomatic; the fetus is at risk

Less severe problems

• Constipation
• Braxton-Hicks contractions - usually felt as 'tightening' rather than pain after 20 weeks
• Round ligament pain - low abdominal or groin pain due to the uterus pulling on the round ligament
• General aches - due to uterine enlargement
• Pelvic girdle pain:
  • Symphysis pubis dehiscence
  • Osteomalacia may present in pregnancy due to increasing vitamin D requirements
• Rectus muscle haematoma - due to rupture of inferior epigastric vessels in late pregnancy:
  • Presents with sudden severe abdominal pain, often after coughing or trauma

History

• Symptoms: pain history; other symptoms - vaginal bleeding, other G-I or urinary symptoms; pre-eclampsia symptoms (e.g. headache, visual change, nausea)
• Fetal movements
• Obstetric history including:
  • Gestation - LMP, certainty of dates, was LMP 'like your normal period?'
  • Conception - was conception planned, unwanted, difficult or assisted
  • Contraception used (coil and POP increase risk of ectopic)

Examination

• General examination - well/ill, signs of sepsis, shock or haemorrhage, blood pressure, urine dipstick protein and glucose.
• Abdominal examination - as for any abdominal pain, assess for tenderness, masses, bowel sounds, peritonitis, urinary retention, hernias; remember that classical signs may be masked by a large uterus.
• Assess the pregnancy and uterus:
  • Palpate uterus for fundal height, contractions or hard uterus, polyhydramnios; in late pregnancy palpate fetal position/presentation.
  • Assess fetal well-being - movements or heartbeat (auscultate, Doppler or CTG).
• Consider vaginal and/or rectal examination:
  • In the community these may be difficult, and should be omitted unless they are likely to add useful diagnostic information that might prevent hospital referral
  • Never do vaginal examination if placenta praevia suspected (vaginal bleeding in 2nd half of pregnancy) - it could cause a massive bleed.
  • Suspected rupture of membranes requires sterile examination and should be done in an obstetric unit.
  • In early pregnancy:
    • Pelvic examination can assess uterine size, adnexal tenderness and pain on cervical movement.
    • For incomplete miscarriage with heavy bleeding, examine cervical os. Products of conception in the os can be removed (using sponge forceps) to reduce bleeding and pain.

Initial investigations

• Pregnancy tests:
  • Modern urine β-HCG tests are sensitive, detecting β-HCG at 25 iu/L (a level normally reached 9 days post-conception).¹¹ Serum testing detects levels down to 5 iu/L. Usually, a urine test is sufficient screening, but if pregnancy or ectopic pregnancy are strongly suspected with a negative urine test, serum testing is definitive.¹²
  • Serial serum β-HCGs aid diagnosis and management decisions for suspected ectopic pregnancy and miscarriage.¹¹
• Blood tests: Cross-match, full blood count, renal and liver function, glucose, clotting screen. Urate for suspected pre-eclampsia. Consider sickle test, calcium, amylase, hepatitis serology.
• Urine: dipstick, microscopy and/or culture. Urine protein quantification for suspected pre-eclampsia.
• CTG for fetal well-being and uterine contractions.
• Ultrasound:
  • First trimester:
    • Ultrasound can confirm whether pregnancy is intra-uterine and viable.
    • From 5+ weeks a sac is visible and from 6 weeks the fetal heartbeat is seen.
    • Transvaginal ultrasound is more sensitive in early pregnancy, and aids diagnosis of ectopic pregnancy.¹¹
    • Free fluid in the pelvis suggests ectopic pregnancy.¹²
  • Second-third trimesters: ultrasound gives information about fetal well-being, the uterus and placenta.
  • Abdominal ultrasound may help with diagnosis, e.g. acute appendicitis, ovarian cysts, gallstones.¹

Further investigations

• If perforated viscus suspected, an upright chest X-ray can be done with lead shielding (discuss with surgeon, avoid unnecessary x-rays).
• Diagnostic laparoscopy is feasible and useful in pregnancy.¹

• Identify emergencies and resuscitate/transfer (see emergencies box).
• Pain relief may be needed. Intravenous opiate analgesia can be given, but titrate small doses, monitor BP in unstable patients² and consider effect on fetus.
• The clinical picture can change over time - re-assessment is an important tool.
• Consider referral/admission if:
  • Serious problems for mother or fetus cannot be excluded.
  • A patient re-consults with undiagnosed pain.
• Combined obstetric and surgical assessment may be needed.
• In early pregnancy, some women with suspected miscarriage or ectopic pregnancy may be referred to early pregnancy units and be discharged home in the meantime. If so, the patient must be well and haemodynamically stable (no syncope, normal and stable vital signs); and she must be able to return to hospital quickly if necessary.
• 'Safety-net' if discharging the patient so she understands when to seek help.