1. Department of Obstetrics and Gynaecology Seoul National University Hospital Seoul Korea
2. Department of Obstetrics and Gynaecology Korea University Hospital Seoul Korea
3. Department of Obstetrics and Gynaecology Seoul National University College of Medicine Seoul Korea
4. Big Data Department National Health Insurance Service Gangwon‐do Korea
5. Graduate School of Statistics Sungkyunkwan University Seoul Korea
6. Innovative Medical Technology Research Institute Seoul National University Hospital Seoul Korea