Postpartum hemorrhage (PPH) is the leading cause of death related to pregnancy. PPH can lead to blood transfusion, disseminated intravascular coagulation (DIC), hysterectomy, or death. The prophylactic administration of uterotonic agents as part of an active management of the third stage of labor has been proven to reduce rates of PPH. However, even with these treatments, PPH rate is still relatively high, and puts women at risk of heavy bleeding and death.

Calcium is a key component in the coagulation cascade and known as factor IV. It has a role in platelet activation, and it is an important co-factor for the activation of factors II and There is a concentration-dependent effect of hypocalcemia on in vitro clot strength in patients at risk of bleeding. Calcium gluconate is the calcium salt of gluconic acid, and it has a relatively strong safety profile.

Hypocalcemia is a poor prognostic factor in actively bleeding patients. Calcium has a positive inotropic effect both on skeletal muscle and smooth muscle. The inotropic effect doesn't skip the myometrium, and it is well-established that hypocalcemia can impair myometrial contractility. As so, calcium channel blockers are prescribed as a tocolytic drug and calcium gluconate should be considered as adjuvant therapy for treating PPH duo to atony, in case of prolonged tocolytic or magnesium sulfate use prior to delivery. Studies have already shown an association between low ionized calcium levels and the risk for severe bleeding. In a pilot randomized controlled trial of patients with risk factors for uterine atony, calcium was shown to reduce uterine atony compared to placebo. However, current studies have small sample size and are limited to a high-risk population. There are no recommendations in current guidelines for monitoring calcium levels or prescribing calcium as a prophylactic measure for the third stage of labor, despite atony and coagulopathy being significant causes of PPH.

HYPOTHESIS: Administration of Calcium Gluconate at the third stage of elective Cesarean delivery will decrease the rates of blood loss during and after the surgery by reducing the rates of uterine atony and development of coagulopathy, thus has the potential of reducing the incidence of PPH and its complications without severe side effects.

After signing a consent form prior to the surgery (at the pre-operative assessment), At the third stage of labor, women who gave their consent to participate in the study will get either 10 ml of Calcium Gluconate 10% solution (containing 0.94 gr of calcium gluconate) diluted in 100 ml of normal saline IV or 110 ml of normal saline IV.

The solutions will be given in addition to Carbetocin (a long acting oxytocin analogue), in both arms. The invastigators will use calcium gluconate during even-numbered months and normal saline during odd-numbered months, or vice versa, according to randomization that will be known to the primary researcher alone.

A blood sample will be drawn at the beginning of the surgery and sent for blood gas analysis, determining ionized calcium levels and coagulation profile. Women with hypocalcemia or hypercalcemia will be excluded from the trial. Only patients with normal calcium levels between 1.0-1.3 mmol/L will be included in this trial.

An ECG strip will be done prior to the surgery, making sure that the patient doesn't suffer from a QT segment abnormality. All patients will be monitored with a 3 lead- ECG prior, during, and 2 hours following calcium administration. Patients with QT interval abnormalities will be excluded from the trial. After the surgery, a blood sample will be drawn and sent to blood gas analysis (determining ionized calcium levels) and for coagulation profile. A complete blood count will be routinely taken for all women the next day. The hemoglobin level will be compared to the hemoglobin level prior to CD.

Decreased mean hemoglobin drop is the primary outcome. the secondary outcomes are described below.

After the primary analysis we will perform a subgroup analysis, determine whether women with high risk for PPH (such as overdistended uterus, abnormal placentation, myomatous uterus, grand multiparty, coagulation disorder, etc.) may benefit from the intervention more than the general population of all participants.

Inclusion Criteria:

- Elective Cesarean Delivery, at Gestational age of 35 weeks or more.

Exclusion Criteria:

• Age younger than 18 years old.
• Patients treated with calcium channel blockers.
• Chronic renal failure and hyperphosphatemia.
• Sarcoidosis.
• Hypocalcemia (ionized Ca<1 mmol/L) or hypercalcemia (ionized Ca> 1.3 mmol/L) before the surgery.
• Any QT abnormalities as evident by ECG before Calcium Gluconate administrations or any known conduction abnormality.