Bariatric Surgery/adverse effects; Deficiency Diseases/etiology; Nutritional Status; Obesity/surgery; Postoperative Complications/epidemiology; Pregnancy Complications/etiology; Adult; Anemia, Iron-Deficiency/blood; Anemia, Iron-Deficiency/epidemiology; Anemia, Iron-Deficiency/etiology; Deficiency Diseases/blood; Deficiency Diseases/epidemiology; Female; Folic Acid/blood; Humans; Iron/blood; Iron Deficiencies; Logistic Models; Multivariate Analysis; Obesity/complications; Postoperative Complications/blood; Preconception Care; Pregnancy; Pregnancy Complications/prevention & control; Retrospective Studies; Vitamin B Deficiency/blood; Vitamin B Deficiency/epidemiology; Vitamin B Deficiency/etiology; Vitamin D Deficiency/blood; Vitamin D Deficiency/epidemiology; Vitamin D Deficiency/etiology; Young Adult