The purpose of the study is to assess potential age-related differences on coagulation profile of patients undergoing Cesarean Section, using thromboelastography (TEG). The investigators will compare coagulation data collected from the study to assess potential differences in coagulation parameters for the following age groups: (i) women less than 35 yrs (ii) women 35 yrs or older.

The purpose of the study is to assess potential age-related differences on coagulation profile of patients undergoing Cesarean Section, using thromboelastography (TEG). The investigators will compare coagulation data collected from the study to assess potential differences in coagulation parameters for the following age groups: (i) women less than 35 yrs (ii) women 35 yrs or older. This study will allow us to collect more information about differences regarding coagulation profile in patients undergoing cesarean section who are less than 35 y vs. 35y or older. This information will add to current knowledge base about potential risk for thrombotic events according with age.

All obstetric patients presenting for elective Cesarean delivery (CD) will be informed about the study prior to and on admission to the labor and delivery unit. Patients will be informed at parents' education classes (during education sessions by obstetric anesthesiologists who are also members of the research team). Potential participants will be approached by a member of the research team prior to surgery. A study investigator will obtain patient written informed consent.

Pre-operatively, blood sampling will take place by venepuncture for the following analysis:

Hematocrit, Platelet count (which are part of standard of care), TEG, prothrombin time (PT), Partial Thromboplastin Time (PTT), International Normalized Ratio (INR), fibrinogen (for research purposes only, unless they are needed for clinical purposes).

The investigators would prefer to avoid taking blood samples from indwelling peripheral IV lines, as the samples will likely be diluted with intravenous fluid and therefore may significantly affect blood sampling analysis. The volumes of blood necessary for TEG analysis are extremely small (1 ml - less than half of a teaspoon - per TEG analysis; total =3 samples), and therefore will not significantly affect any potential degree of hemorrhage or total blood loss incurred. The volumes of blood for laboratory analysis will also be small (4-5 ml - about 1 teaspoon - for each research sample: total =3 samples), and will not affect overall blood loss. No randomization will be possible. TEG and laboratory samples will be taken at the following time intervals: prior to anesthesia in the preoperative holding unit, post-operative days one and three.

Data will be assessed for normality using normality plots and the Kolmogorov-Smirnov test. Normally and non-normally distributed TEG parameters before and after CD (PACU samples) will be assessed by using the paired t-test and Wilcoxon signed-rank test respectively. The percentage change from baseline for each TEG parameter and Hb before and after CD will also be calculated. Longitudinal analysis of individual changes for each TEG parameter will be performed using mixed effects regression modeling, due to the non-uniformity of time-intervals and to account for correlation among repeated measurements on the same participants. The investigators will examine longitudinal models for individual TEG parameters as a dependent measure, with study group as a fixed factor, and number of previous cesarean section, total blood loss, IV fluids, platelet count and fibrinogen counts as potential covariates (tbc). Separate models will incorporate age as continuous independent variable (as both a fixed and random effect). The investigators will analyze these data using SAS version 9.2 (SAS Institute, Cary, N.C., USA).

Study data will be stored in secured, locked storage boxes which will only be accessed by study investigators. Samples and labels will be identified using a numerical system based allocated prior to the start of the study. Only investigators directly involved in the study will have access to the study data and other related documents.

Study data will be protected as follows:

Hard data will be stored in secure box-files kept in locked file cabinets; databases with study data will be password-protected. Study information will be coded in advance using a numerical coding system not linked to the patients' medical record number or other PHI. Coding will be performed when data is entered into the database. Only study investigators will have access to the coding system for de-identifying data. All codes used to protect study data and confidential information will be used solely by study investigators. All codes used for data- protection will be known only to the study investigators, and software-protection and encryption programs will be used as appropriate.

TEG will be performed by study investigators on the labor and delivery unit. Blood samples will be destroyed after TEG analysis. Other laboratory samples will be analyzed as per normal procedure.

Electronic data will be stored at the Stanford File Management Tool. Only researchers and research staff will be granted password-protected access to identifiable and coded data stored on this server.

All persons involved in this study will receive appropriate training and abide by confidentiality guidelines to protect the subject's privacy. All HIPAA rules and regulations will be strictly followed.

Inclusion Criteria:

• All obstetric patients with singleton pregnancies admitted to the labor and delivery unit at LPCH who undergo elective Cesarean delivery with neuraxial anesthesia.
• We will enroll only healthy patients with singleton pregnancies and whose pregnancy is not result of in vitro fertilization.

Exclusion Criteria:

• Patients with underlying coagulation disorders.
• Patients with thrombocytopenia.
• Patients with pregnancy-induced hypertension, pre-eclampsia.
• Patients requiring the following medications prior to surgery: non-steroidal anti-inflammatories, aspirin, anticoagulants.
• Patients requiring non-elective Cesarean delivery.
• Patients with significant obstetric or medical disease.
• No patients <18 years of age will be recruited.

Our study population will be obstetric patients undergoing delivery on the labor and delivery unit at Lucile Packard Children's Hospital (LPCH).