To assess the efficacy and safety of alternative magnesium sulfate regimens when used as single agent tocolytic therapy for prevention of preterm labour in patients with symptomatic placenta previa and subsequent changes in the cervical length .

Placenta previa is implantation of placenta on or near internal os .It is classified into major degree when lower edge of placenta lies within 2 cm from internal os , and minor degree if lower edge of placenta at lower uterine segment but more than 2 cm from internal os .

There are many risk factors for developing placenta previa including multi parity , multiple pregnancy , increased maternal age (>35y ) , previous uterine surgery , history of placenta previa (4-8%) .

A significant degree of uterine contractility has been observed with symptomatic placenta previa. It is directly associated with vaginal bleeding. However, a large percentage of women who have placenta previa associated with haemorrhage will experience subclinical uterine contractions before the onset of overt vaginal bleeding. Therefore, the use of tocolytic agents in management of placenta previa seems reasonable .

Magnesium sulfate alters calcium up take, binding and distribution in smooth muscles of the uterus, so reduces the frequency of cell depolarization and inhibits myometrial contraction .

In addition to its tocolytic action magnesium sulfate also provide neuroprotection to preterm infant . .

At women Health Hospital, Assiut University, Egypt our policy is using magnesium sulfate as first line for tocolysis for placenta previa patients with preterm uterine contractions. By giving a loading dose of 4 g on 150 ml saline intravenous infusion over 20 minutes, and a maintenance dose of 6g/6h on 500 ml saline slow intra venous infusion

Inclusion Criteria:

1. Singleton pregnancy.
2. Gestational age between 28 weeks to 37 weeks.
3. Patients presented to the hospital with per vaginal bleeding and in whom a clinical diagnosis of placenta previa is confirmed by trans vaginal ultrasound.
4. Placenta previa with preterm uterine contractions (< 3 contractions in 10 minutes)
5. Ability to provide informed consent.

Exclusion Criteria:

1. Placental abruption .
2. Women with placenta previa and severe attack of bleeding need immediate termination
3. Clinical criteria of intra uterine infection.
4. intrauterine growth restriction .
5. Fetal anomalies.
6. Fetal distress.
7. intrauterine fetal death.
8. Preterm rupture of membrane
9. High order multiple pregnancies.
10. Treatment with any tocolytic agent before maternal transport.
11. Inability or refusal to provide informed consent.
12. Women with any contraindication for use of magnesium sulfate as patients with renal failure.
13. Patients with bleeding disorder or on anticoagulant therapy .

only females