Study population
A flowchart of patient enrollment is shown in Fig. 1. Using the KNHI claims database, we identified all women who gave birth from January 2007 to December 2015. Inclusion criteria were as follows: women who gave birth between January 2006 and December 2016, and had undergone the National Health Screening Program for Infant and Children (NHSP-IC) visit to evaluate neonatal characteristics. Women with no or missing NHSP-IC data were excluded from this study. This study was approved by the Institutional Review Board of Korea University Medical Center (2020GR0109).
We identified pregnant women who underwent non-obstetric surgery from the database. Patients who underwent non-obstetric surgery at the time of cesarean delivery were excluded. In this study, non-obstetric surgeries (by laparoscopy or laparotomy) included the two most common operative procedures for benign diseases: appendectomy and adnexal mass resection. The operative procedures were identified by the presence of a Korea Medical Insurance electronic data interchange (EDI) code (Appendectomy: Q2861/Q2862/Q2863, Adnexal mass resection: R4430/R4421). Laparoscopic surgery was identified by the associated Korea Medical Insurance EDI code (N0031001).