Pregnant patients may present to emergency with new or exacerbations of chronic pain. Commonly this can include lower back pain (LBP), pelvic girdle pain (PGP), and abdominal pain.

• Effects on the pregnancy and fetus need to be considered when deciding on an analgesic.
• There are some important diagnostic considerations in a pregnant patient presenting with abdominal pain.

ABDOMINAL PAIN CONSIDERATIONS

History

• Characterize pain.
• Current pregnancy history (dates, ultrasounds, complications).
• Vaginal bleeding, or leaking fluid.
• Fetal movements (in later half of pregnancy).
• Past OB history (eg. Preeclampsia, previous C-section).

Physical Exam

• Vital signs including blood pressure.
• Examine abdomen.
• SFH, fetal HR, cardiotocography if considering contractions, sterile pelvic exam if indicated.

Initial Investigations

• Main imaging modality used is abdomen/pelvic US.
• Transvaginal US useful especially for early pregnancy.
• Beta-hCG, CBC, type, and screen if vaginal bleeding.
• Consider LFT, kidney function, urine dip.

Some considerations for differential for abdominal pain during pregnancy

OBSTETRIC (EARLY)

• Miscarriage: often the first trimester, can be vaginal bleeding, see PEC summary “1st Trimester Bleeding: Miscarriage”.
• Ectopic Pregnancy: often presents as first trimester abdominal/pelvic pain, can be vaginal bleeding, see PEC summary “1st Trimester Bleeding: Ectopic Pregnancy”.

OBSTETRIC (LATER)

• Placental Abruption: can present with abdominal pain, vaginal bleeding, uterine tenderness.
• Uterine Rupture: at risk if previous C-section or recent abdominal trauma, can present with abdominal pain, bleeding, peritoneal signs, abnormal FHR, urgent intervention required.
• Labor: Uterine contractions increasing in frequency & intensity with cervix changes, patient may note gush of fluid or small amount of blood.
• Intra-amniotic infection: fever, abdominal pain, leukocytosis, tender uterus.

LIVER DISEASE SPECTRUM (USUALLY LATER)

• Acute Fatty Liver: nausea, vomiting, abnormal LFTs, may have abdominal pain.
• Pre-eclampsia: new-onset HTN, proteinuria/decreased kidney function, may have abdominal pain.
• HELLP: abnormal LFTs, low platelets, hemolysis on blood smear, often presents with abdominal pain & can be associated with risk of hepatic rupture.

Also consider regular differential for abdominal pain such as obstruction / appendicitis / gall stones / kidney stones / pyelonephritis / UTI / ovarian torsion / ovarian cyst rupture / etc.

Common benign causes include round ligament pain earlier in pregnancy and fetal movements later in pregnancy.

Non-Pharmacologic treatments

• Lifestyle modifications such as exercise (especially helpful for back pain).
• Physiotherapy.
• Specific supports/braces (eg. Pelvic belts for pelvic girdle pain).
• Acupuncture.

Pharmacologic (Lowest dose for shortest duration)

Acetaminophen

• Generally first line.
• Not associated with any major congenital malformations or fetal death² .
• Some studies suggesting association with childhood ADHD & asthma -> reviews of studies note many confounding variables with no definitive causal link^1,2,4.
• Max 1g q6hrs (max 4g in 24hrs)² .

NSAIDs

• Safety depends on timing in pregnancy.
• Inconsistent evidence for association with 1^st trimester miscarriage. Where associations are seen, tend to be more with diclofenac & indomethacin rather than ibuprofen² .
• No significant evidence to support NSAIDs cause congenital malformations².
• Between 20-30 weeks NSAIDs should be avoided and are contraindicated 30+ weeks due to risk of oligohydramnios/kidney injury and premature ductus arteriosus closure^1,2,5.

Opioids

• Short course of opioids can be used for moderate-severe pain that is not responsive to non-pharmacologic options or acetaminophen (eg. Morphine)^1,2,4 .
• Recommend consulting obstetrics provider.
• Case reports of neural tube and heart defects following opioid use in early pregnancy reported by the FDA as a possible risk, but limited evidence^1,2,4.
• Use later in pregnancy has risk for neonatal respiratory depression.
• Prolonged use in pregnancy can result in neonatal abstinence syndrome – resulting in some problems with feeding, sleeping, temperature regulation.
• Severe neonatal abstinence syndrome can cause neonatal respiratory distress, seizures, failure to thrive, developmental delay, and may require a morphine taper after birth.

1. Antenatal and Postnatal Analgesia: Scientific Impact Paper No. 59
   Bisson DL, Newell SD, Laxton C; Royal College of Obstetricians and Gynaecologists. . BJOG. 2019 Mar;126(4):e114-e124.
   -PubMed

   
   

2. Medication Use and Pain Management in Pregnancy: A Critical Review. Pain Pract.
   Black E, Khor KE, Kennedy D, Chutatape A, Sharma S, Vancaillie T, Demirkol A. 2019 Nov;19(8):875-899.
   -PubMed

   
   

3. Interventions for preventing and treating low-back and pelvic pain during pregnancy.
   Liddle SD, Pennick V.  Cochrane Database Syst Rev. 2015;(9)
   -PubMed

   
   

4.  FDA Drug Safety Communication: FDA has reviewed possible risks of pain medicine use during pregnancy.
   US Food and Drug Administration. FDA; 2015. 

   
   

5. FDA recommends avoiding use of NSAIDs in pregnancy at 20 weeks or later because they can result in low amniotic fluid. 
   US Food and Drug Administration. FDA; 2020.

    

   
   

6. Patient information on back and pelvic pain:

   Back Pain During Pregnancy 

   Pelvic girdle pain and pregnancy 

   
   

7. Information about pain management during labor.
   Perinatal Services BC 
   -PHSA