The primary goal of this investigation is to describe perioperative thrombin generation in neonates undergoing placement of a Blalock-Taussig (BT) shunt to better understand the coagulation changes that precipitate postoperative shunt occlusion.

To accomplish our goal, the investigators will measure preoperative levels of one major procoagulant (prothrombin) and one major anticoagulant (Antithrombin). The investigators will also measure preoperative and postoperative thrombelastograms (TEG) and preoperative and postoperative thrombin generation curves (TGC).

Inclusion Criteria:

1. Full-term neonates (37-42 weeks gestational age)
2. Apgar score of 7 or more at 5 minutes after delivery
3. Surgical placement of BT shunt or repair of an aortic coarctation
4. Parent or legal guardian willing to participate, and able to understand and sign the provided informed consent

Exclusion Criteria:

1. Preterm neonates (less than 37 weeks gestation)
2. Apgar score of less than 7 at 5 minutes after birth
3. Emergent procedure
4. Surgical procedure other than placement of BT shunt or repair of aortic coarctation
5. Neonates with a known coagulation defect or coagulopathy
6. Mother with a known coagulation defect or coagulopathy
7. Parent or legal guardian unwilling to participate or unable to understand and sign the provided informed consent

1. Full-term neonates (37-42 weeks gestational age)
2. Apgar score of 7 or more at 5 minutes after delivery
3. Surgical placement of BT shunt or repair of an aortic coarctation
4. Parent or legal guardian willing to participate, and able to understand and sign the provided informed consent