Inclusion Criteria for CD patients:  To be pregnant in the 1st trimester or planning pregnancy. Diagnosis of Crohn's disease is confirmed by clinical, endoscopic, radiological and histological features All eligible should sign the consent form  Inclusion Criteria for Healthy Control:  To be pregnant in the 1st trimester or planning pregnancy Subjects without a diagnosis of IBD All eligible should sign the consent form  Inclusion Criteria for non-pregnant CD patients  Diagnosis of Crohn's disease is confirmed by clinical, endoscopic, radiological and histological features All eligible should sign the consent form  Exclusion Criteria for all groups:  Co-morbidities, such as type I or type II diabetes, autoimmune diseases, cancer, HIV Inability to give informed consent Probiotics. prebiotics and antibiotics use in the past 3 months