Main Findings
The present study on appendectomy (both definite and suspected cases) in pregnant women at a hospital normally carrying out surgery in pregnancy, showed a low risk for pregnancy and other surgical postoperative complications. Immediate surgery (within 6 hours) seems to significantly reduce the risk for appendix perforation, but at the cost of a high rate of surgery for an innocent appendix, as reported in a previous paper [10]. The low risk for preterm delivery and foetal loss seen in this study is in contrast to previously reported increased risk for fetal loss, preterm delivery, low birth weight, and foetal growth restriction [10, 11]. Indeed, we were unable to show any increase in risk beyond those normally seen in pregnancy. However, for one of the newborns in this study we could not rule out rule out persistent low-grade appendicitis with haematogenous spread leading to meningitis.
The risk for appendicitis is reported to be lower in pregnancy [2,12,13]. In this large sample of non-pregnant control women the IR was 132/100 000. We found a strong age-dependency for appendicitis with the maximum IR being 137/100 000 between 20 and 24-years-of-age, declining to 89 between 40 and 44 years. The rate of appendectomy among women giving birth was 115/100 000, i.e., 1/870 women giving birth. This is close to a prior large (n = 778) Swedish study during 1973 to 1981, one in 936 [12]. In that study 23% of early appendectomies were innocent as compared to 4% in our material (p < 0.001) [19]. In late pregnancy the percentage of innocent appendix was, however, similar as the present 36% [12].
Clearly, a lower time to surgery in pregnancy will lower the risk of outcome regarding perforated appendicitis with its complications. The decision to operate would be further improved by better diagnostic tools to indicate whether or not appendicitis is present, to avoid perforation. When positive, ultrasound gave correct diagnosis in 2/3 of the cases. MRI is excellent in diagnosing appendicitis in pregnancy and recommended in current international guidelines [14]. Thus, although we did not have access to MRI, it would presumably have improved pre-operative diagnostics and decrease the number of innocent appendices in late pregnancy. Furthermore, LapApp used as first choice during the first half of pregnancy, may have lowered the threshold for surgery as it provides diagnostic information on other pathological conditions present. Another Swedish study assessing appendectomies 1973 to 2013 with 5.8% LapApp, showed a low incidence in late pregnancy appendectomies and a high rate during peripartum period [2]. The high peripartum rate is supposedly due to a high rate of combination Cesarean section and appendectomy close to delivery, but appendectomyen passant cannot be excluded [2].
Laboratory biomarkers also aid decision-making in the pregnant patient with signs of appendicitis. All pregnant women with perforated and half of non-perforated appendicitis in the present cohort had low plasma sodium levels (< 136 mmol/L), which is in-line with prior reports [7,15]. Most pregnant women (60%) had increased CRP (> 20 mg/L), but 15% had CRP < 10 mg/L at the time of diagnosis.
The risk for a thromboembolic event is increased about 10 times during pregnancy, and a further 5 times after surgery. The recommendation to give thromboprophylaxis for one week was followed in 74% of cases [16,17]. No postoperative thrombotic event was seen in our cohort.