Background: Appendicitis during pregnancy is rare but still the most common reason for non-obstetric surgery during pregnancy. Evidence on incidence patterns across gestation, pregnancy outcomes, and management is limited and often methodologically heterogeneous. The overall aims were to investigate the incidence and management of suspected appendicitis during pregnancy, and to assess pregnancy outcomes following appendicitis and/or appendectomy.

Methods: Papers I–II are nationwide, register-based cohort studies using the Swedish Medical Birth Register and National Patient Register (1973–2013/2023).The incidence of appendicitis across pregnancy trimesters and during the intervals one year before and two years after pregnancy was estimated and reported as incidence rates (IR) and standardized incidence ratios (SIR). Outcomes included IUFD, preterm birth, cesarean section, Apgar <7 at 5 minutes, SGA and neonatal mortality. Paper II additionally used matched case–control analyses by gestational age at exposure to estimate odds ratios for outcomes. Paper III is a nested case–control study (2010–2013) of pregnant patients undergoing appendectomy or admitted with nonspecific abdominal pain, evaluating diagnostic imaging and the AIR score (discrimination by AUC; sensitivity/specificity thresholds). Paper IV is a randomized, single-blind national survey of on-call surgeons (spring 2025) using parallel case scenarios (pregnant vs non-pregnant), with primary outcomes of management choices and adherence to AIR-based recommendations; TFA and PRA scales were included evaluating personality traits linked to tolerance for uncertainty and risk attitude among surgeons.

Main Results: Incidence of appendicitis was markedly lower during pregnancy, especially in the third trimester, followed by a peripartum spike and a postpartum elevation that normalized within two years. In 1973–2023 data, appendicitis/appendectomy during pregnancy was associated with moderate increased risks of preterm birth (overall OR ~1.9), cesarean delivery (OR ~1.6), low 5-minute Apgar, and neonatal mortality, but not IUFD or SGA. Risks rose steeply with advancing gestational age at exposure; at 32–36 weeks, preterm birth reached 43.1% (aOR 9.84, 95% CI 8.21–11.80). Early-pregnancy surgery was not associated with excess preterm risk after adjustment, whereas late-pregnancy surgery and conservative management were. Synchronous cesarean and appendectomy increased with gestation. The AIR score performed well in pregnancy (AUC 0.88–0.90); sensitivity for complicated appendicitis was 100% at ≥4 points and specificity for any appendicitis 97% at ≥9. Imaging (mainly US) showed limited performance (sensitivity 45%, specificity 42%). In randomized questionnaires with clinical case scenarios (response rate 41.5%, n=370), pregnancy status shifted surgeons decisions toward observation/imaging in low–intermediate probability scenarios and greater preference for open surgery in high probability. Pregnancy and the reported use of a clinical score were independently associated to adherence to AIR-based recommendations in the intermediate probability case scenario. Clinical experience but not TFA or PRA scores were associated with management preferences.

Conclusions: Pregnancy appears transiently protective against appendicitis, yet appendicitis in late gestation is linked to substantially increased obstetric intervention and preterm birth—at least partly iatrogenic through synchronous delivery. Structured clinical assessment remains valid in pregnancy; the AIR score reliably stratifies risk, whereas routine imaging performance is limited. Management strategies should be tailored to gestational age, judicious use of imaging, and adherence to validated clinical algorithms. These findings support the need for gestation-specific guidelines and pathways to balance maternal surgical safety with fetal outcomes.