Patients with enlarged yolk sacs are usually allowed to have heparin if it is not contraindicated. Heparin is sodium heparin or calcium heparin, which is usually used in pregnant women to protect the fetus, and low molecular weight heparin calcium injection is contraindicated in the following conditions. 1. Hypersensitivity to low molecular heparin or any of the excipients in low molecular heparin injection. 2. history of thrombocytopenia with low molecular heparin. 3. active bleeding or increased risk of bleeding associated with abnormal hemostasis, except for disseminated intravascular coagulation not caused by heparin. 4. Organic injuries that may cause bleeding (e.g., active peptic ulcer). 5. Hemorrhagic cerebrovascular accident. 6. Acute infectious bacterial endocarditis. Patients with large yolk sacs are usually allowed to have heparin if the above contraindications do not exist. Heparin is a drug often used by pregnant women to inhibit thrombosis and play an anticoagulant role, for some pregnant women with thrombophilia or rheumatoid immune diseases, usually need to use heparin throughout pregnancy. It is recommended that the patient actively communicate with the doctor, who will consider whether to use heparin according to the actual situation.