Analysis of Factors Associated With The Occurrence of Amniotic Fluid Entry in Patients Undergoing Caesarean Section

To compare serum STN （Neuraminic acid-N-acetylgalactose）antigen concentrations in patients undergoing cesarean section and to study the factors associated with amniotic fluid entry.Compare the serum complement C4 concentration in patients in the amniotic fluid admission group with those in the non-admission group to study whether amniotic fluid admission triggers the body's immune response.To record the patients' blood pressure, heart rate, blood oxygen, and the occurrence of related symptoms and adverse reactions at the time of admission, at the time of blood collection, at the time of discharge from the room, and at the time of the occurrence of haemodynamic changes.