Incidence of Appendicitis in Pregnancy
The incidence of appendicitis is NOT increased during pregnancy, occurring in approximately 1 in 500 to 1 in 1,500 pregnancies, which is similar to or slightly lower than the general population rate. 1, 2, 3, 4
Epidemiological Data
The reported incidence ranges from 0.05% to 0.2% of all pregnancies, translating to approximately 1 in 500 to 1 in 1,500 deliveries 1, 2, 3, 4
Appendicitis occurs most frequently during the second trimester (approximately 40-50% of cases), followed by the third trimester (30-50%), and least commonly in the first trimester (20-30%) 1, 5, 3
A large multicenter study found that pregnant women accounted for only 1 in 20 women of childbearing age presenting with appendicitis, confirming that pregnancy itself does not increase susceptibility 6
Critical Clinical Distinctions
The key issue is not increased incidence, but rather increased risk of complications when appendicitis does occur:
Pregnant women are more likely to present with perforated appendicitis (perforation rates of 25-55% reported) compared to non-pregnant patients 1, 5
The interval between symptom onset and surgery is the primary predictor of perforation: perforated cases averaged 109.5 hours versus 35.1 hours for non-perforated cases 5
Delayed diagnosis contributes to higher perforation rates, not an inherently more aggressive disease process in pregnancy 5, 2, 3
Maternal and Fetal Outcomes
When perforation occurs, there is a significantly increased risk of fetal loss (up to 25% with perforation versus 1.7% without) and preterm labor (25% versus 1.3%) 5
First and second trimester appendectomy carries higher risks: spontaneous abortion in 33% of first trimester cases and premature delivery in 14% of second trimester cases 2
Third trimester appendectomy has better outcomes with minimal pregnancy complications when diagnosed and treated promptly 2
Diagnostic Approach
MRI is the preferred imaging modality when ultrasound is inconclusive, as recommended by the American College of Radiology 6, 7
Initial ultrasound is diagnostic in approximately 58% of pregnant patients; delayed repeat ultrasound during observation can increase diagnostic yield without compromising maternal or fetal safety 6
Surgery should be performed within 24 hours of diagnosis to minimize perforation risk and adverse outcomes 6