Clinical Review - Abdominal pain in pregnancy

By Mr Bright Gyampoh, senior specialist registrar, Mr Antonios V Antoniou, consultant gynaecologist and obstetrician, and Mr Nilesh Agarwal, specialist registrar, Newham University Hospital, London.

Ovarian cyst: cysts may be pregnancy or non-pregnancy related
Ovarian cyst: cysts may be pregnancy or non-pregnancy related

Section 1: Incidence and diagnosis
Abdominal pain is one of the most common symptoms in pregnancy. Almost all pregnant women experience some pain at various stages before they go into labour.

This varies from a benign symptom that may settle spontaneously or with simple analgesia, to an acute abdomen.

The incidence of an acute pathology or acute abdomen in pregnancy is reported to be one in 500-6351,2 and surgical intervention rates are high.

Abdominal pain in pregnancy can be due to physiological changes or it can be pathological; concern for the fetus may exacerbate the pain.

Differentiating between physiological and pathological causes can be a diagnostic and management dilemma.

Difficulties associated with diagnosis, for example, avoiding exposure of the fetus to high-dose radiation, may delay invasive diagnostic and therapeutic procedures and definitive treatment, which can lead to increased morbidity and mortality.

It is useful to categorise potential causes as related or unrelated to pregnancy (see boxes).

NON-PREGNANCY RELATED CAUSES OF ABDOMINAL PAIN
  • UTI
  • Pyelonephritis
  • Gastritis, heartburn
  • Gastroenteritis
  • Cholelithiasis
  • Peptic ulcer
  • Constipation
  • Ventral hernia
  • Appendicitis
  • Cholecystitis
  • Salpingitis
  • Tubo-ovarian abscess
  • Pelvic inflammatory disease
  • Ovarian torsion
  • Adnexal torsion
  • Torsion of subserous fibroid
  • Rectus haematoma
  • Acute pancreatitis
  • Nephrolithiasis
  • Bowel obstruction
  • Mesenteric adenitis
  • Right-lower lobe pneumonia
  • Bowel cancer
  • Sickle cell disease (crises)
  • Malaria
  • Diabetic ketoacidosis
  • Pneumonia
  • Inferior MI
  • Inflammatory bowel disease

 

PREGNANCY-RELATED CAUSES OF ABDOMINAL PAIN
Physiological
  • Round ligament pain
  • Pain related to dilation of ureter
  • Raised progesterone
  • Braxton-Hicks contractions
  • Pressure effects of fetal head (engaged and breech)
Pathological: in early pregnancy
  • Threatened miscarriage
  • Gestational trophoblastic disease
  • Corpus luteum cyst (non-haemorrhagic or haemorrhagic)
  • Adnexal torsion
  • Acute retention of urine
  • Ruptured ovarian (corpus luteum) cyst
  • Haemorrhagic ovarian cyst
  • Miscarriage
  • Ectopic pregnancy
  • Ovarian hyperstimulation syndrome
Pathological: in late pregnancy
  • Threatened pre-term labour
  • Pubic symphysis diastasis
  • Haematoma of rectus sheath
  • Acute polyhydramnios
  • Degenerating uterine fibroids
  • Placental abruption
  • Uterine torsion
  • Chorioamnionitis
  • Pre-eclampsia
  • Acute fatty liver of pregnancy
  • Abdominal venous thrombosis
  • Uterine rupture
  • Ruptured liver

Section 2: Physiological causes
Round ligament pain is more common in the late first trimester and second trimester. Pain occurs due to stretching of the round ligament as the gravid uterus enlarges from the pelvis into the abdomen.

Diagnosis is by exclusion of other causes of lower abdominal pain; treatment is mainly reassurance and simple analgesics such as paracetamol. If pain is so severe as to require stronger analgesia, admission to exclude other causes is advisable.

Braxton-Hicks
Braxton-Hicks contractions occur intermittently throughout pregnancy and prepare the uterus and cervix for labour. They become more obvious and frequent as the pregnancy progresses, occurring several times an hour or several times a day.

Some researchers have proposed that these contractions do not lead to cervical changes and that ripening only occurs in pre-labour, when the first co-ordinated contractions of labour start.3,4

Although these contractions are pain-free in the majority of women, painful Braxton-Hicks contractions have been reported in some cases.

They are usually experienced during the last three months of pregnancy and are reported as vague backache, which is minimally uncomfortable and does not require analgesia. After excluding other causes, the only action required is simple reassurance.

Section 3: Pathological causes

Early pregnancy
Miscarriage can occur early (up to 12 weeks) or late. It affects 10-20 per cent of confirmed pregnancies, the majority early.

The most common symptoms are vaginal bleeding and abdominal pain.

Up to about 85 per cent of miscarriages are of a genetic nature.5 Other causes include uterine abnormalities (septate uterus, fibroids or incompetent cervix), maternal conditions (diabetes, thyroid disease and thrombophilias), infection of the uterus, smoking, and alcohol and drug use.

Adnexal torsion, twisting of the ovary and sometimes the fallopian tube, obstructs the arterial supply causing ischaemia. The ovary may contain a cyst. Pedunculated fibroids may also undergo torsion.

Adnexal torsion presents with a history of intermittent abdominal pain that becomes constant. There may be low-grade pyrexia; FBC will demonstrate leukocytosis. Diagnosis is clinical, with ultrasound detecting cysts or by laparoscopy.

Ectopic pregnancy occurs most commonly in the fallopian tube. It may rarely occur in the cervix and intestines, and even in the appendix.

Reported incidence of ectopic pregnancy is one in 60-250 pregnancies, depending on genital tract pathology and contraceptive practices.6

The most common clinical presentation is amenorrhoea and abdominal pain, with or without vaginal bleeding. Risk factors include pelvic inflammatory disease, tubal surgery, previous ectopic, previous termination of pregnancy, IVF and ovulation induction.

Clinicians should have a high index of suspicion in a woman presenting with abdominal pain, with or without bleeding, in very early pregnancy.

Acute urinary retention mainly occurs in the second trimester as a result of a retroverted uterus stretching the urethra, which obstructs urine outflow. The patient will present with abdominal pain and urine retention.

Late pregnancy
Uterine fibroids are benign tumours that contain estrogen and progesterone receptors. As fibroids enlarge during pregnancy, the central areas can suffer relative ischaemia (red degeneration), which usually presents with constant pain, localised to the side of the uterus where the fibroid is. Reassurance and adequate analgesia are the mainstays of treatment.

Uterine torsion in pregnancy, a rare complication, refers to a rotation of the uterus by more than 45 degs on its long axis. It may be asymptomatic, depending on the degree of torsion. The most common symptom is abdominal pain, varying from non-specific mild discomfort to symptoms of an acute abdomen with shock.

A ruptured uterus can occur in women who have had a previous caesarean section, hysterotomy or myomectomy, or a uterus that has been previously perforated, for example, in a termination.

This should be a differential diagnosis in such women presenting in later pregnancy or early labour with acute abdominal pain. Treatment is urgent laparotomy.

Placental abruption usually presents after the second trimester with acute abdominal pain with or without vaginal bleeding. It may present with only mild pain, making a high index of suspicion essential.

Risk factors include a history of placental abruption during a previous pregnancy, high BP, multiple pregnancies, heavy alcohol or cocaine use, or injury to the abdomen.

Premature rupture of membranes presents before 37 weeks of gestation and predisposes the patient to ascending infection (chorioamnionitis). It can precipitate pre-term labour. The patient presents with vaginal discharge, abdominal pain and maternal tachycardia. Complications include fetal death and maternal septicaemia, and there is a risk of maternal mortality.

Section 4: Pain unrelated to pregnancy
Reflux oesophagitis is common in late pregnancy and presents with a burning pain in the upper epigastrium that is aggravated by lying flat or bending.

It occurs because of relaxation of the lower oesophageal sphincter, caused by progesterone, and as the distal oesophagus is pushed upward by the gravid uterus. Treatment is to advise more frequent, smaller meals and antacids.

Appendicitis is a common cause of an acute abdomen in pregnancy (about one in 1,500 pregnancies).7 Symptoms include anorexia, nausea, vomiting and fever, along with pain.

Patients may also present with diarrhoea and contractions.

In later pregnancy, pain may be atypically located in the right hypochondrium (because of displacement of the caecum by the gravid uterus). There is usually a leukocytosis; however, serial white cell counts are required because mild leukocytosis is normal in pregnancy. Delayed diagnosis is associated with a greater risk of complications.8

Treatment is appendicectomy when clinical suspicion is high. Pre-term labour is a recognised complication of surgery.

Cholelithiasis and UTIs
Biliary stasis, delayed emptying and raised cholesterol levels during pregnancy predispose to cholelithiasis. This presents with nausea, vomiting and colicky abdominal pain in the right upper quadrant, and is exaggerated by eating fatty foods.

Clinical signs include tenderness; ultrasound scan shows an enlarged gall bladder with stones in the bile duct.

Treatment is conservative where possible, but surgery may be required. Laparoscopic cholecystectomy is safe and effective.9 Acute cholecystitis has similar presentation, but is accompanied by pyrexia. Cholecystitis is second only to appendicitis as the most common surgical condition in pregnancy.9

UTIs commonly present with pain suprapubically and in the lumbar region. Symptoms may include vomiting, pyrexia and rigors. Symptomatic bacteriuria affects 17-20 per cent of pregnancies and is linked to pre-term premature rupture of membranes and pre-term labour; it increases the risk of morbidity and mortality to the woman.

Dipstick testing is not sufficiently sensitive and culture is the investigation of choice. Symptomatic and asymptomatic infections should be treated with antibiotics and good hydration to reduce incidence of pyelonephritis and pre-term labour.

References
1. Coleman MT, Trianfo VA, Rund DA. Nonobstetric emergencies in pregnancy: trauma and surgical conditions. Am J Obstet Gynecol 1997; 177: 497-502.

2. Kammerer WS. Nonobstetric surgery during pregnancy. Med Clin North Am 1979; 63: 1157-64.

3. Murray I. Change and adaptation in pregnancy. In: Fraser DM, Cooper MA (eds). Myles' Textbook for Midwives. Edinburgh, Churchill Livingstone, 2003.

4. Baker P. Obstetrics by Ten Teachers. London, Hodder Arnold, 2006.

5. Hamerton JL. Human Cytogenetics. Vol 2: Clinical Cytogenetics. New York, Academic Press, 1971.

6. Nair U. Acute abdomen and abdominal pain in pregnancy. Curr Obstet Gynaecol 2003; 13: 14-20.

7. Pastore PA, Loomis DM, Sauret J. Appendicitis in pregnancy. J Am Board Fam Med 2006; 19: 621-6.

8. Tamir IL, Bongard FS, Klein SR. Acute appendicitis in the pregnant patient. Am J Surg 1990; 160: 571-6.

9. Ghumman E, Barry M, Grace PA. Management of gallstones in pregnancy. Br J Surg 1997; 84: 1646-50.

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