Type of study: prospective descriptive monocentric study

Population: 2 groups: -Exposed group: pregnant patient between 24AW+0day and 32AW+0day receiving magnesium sulfate for fetal neuroprotection in the doubt of premature delivery

• Control group: pregnant patient between 32AW+1day and 35AW+0day in the same context not requiring magnesium sulfate due to their gestationnal age.

Criterion(s) of judgment: Appearance of a change in short-term variability after injection of magnesium sulfate in the exposed group compared to the control group.

Schedule: Inclusion from February 20 to August 31, 2018

Expected results and prospects:

The general impression during my semester at the Jeanne de Flandre maternity clinic in Lille was the variability improves after injection of the magnesium sulfate used in the premature infant as a neuroprotective. The investigators would like to proove that the use of magnesium sulfate as neuroprotective in premature fetuses would improve the fetal heart rate by increasing variability.

In the literature there are numerous publications on the effects of magnesium sulfate used as tocolytic (higher doses) in the threats of premature labour, generally showing a variability and number accelerations decreases without increase the number of decelerations. Is this effect is the same as the doses used for fetal neuroprotection?

Expected benefits of the research:

Magnesium sulfate used on premature infants for fetal neuroprotection has an impact on fetal heart rate, including variability and number of accelerations.

Investigation plan:

Exposed group: fetuses aged 24 + 0AW to 32 + 0AW and benefiting from MgSO4 for neuroprotective purposes, with decision of extraction or spontaneous labour or induced labour:

1 FHR + STV before MgSO4 bolus

1. FHR + STV 10 minutes after the start of the MgSO4 bolus

   Control group: fetuses aged 32 + 1SA to 35 + 0SA without MgSO4, with extraction decision or spontaneous labour or induced labour:

2. FHR + STV at 10 minutes interval : 1 STV at the entrance if suspicion premature labour (in the delivery room) then another 10 minutes after; 2 STV at 10 minutes interval if extraction decision.

Statistical Analysis Plan:

Measurement of the STV value difference before / after MgSO4 in the exposed group and the STV value difference between the 2 measurements in the control group and comparison of these differences.

Inclusion Criteria:

Exposed group: fetuses aged 24 + 0AW to 32 + 0AW and benefiting from MgSO4 for neuroprotective purposes, with decision of extraction or spontaneous labour or induced labour:

1 FHR + STV before MgSO4 bolus

1. FHR + STV 10 minutes after the start of the MgSO4 bolus

   Control group: fetuses aged 32 + 1SA to 35 + 0SA without MgSO4, with extraction decision or spontaneous labour or induced labour:

2. FHR + STV at 10 minutes interval : 1 STV at the entrance if suspicion premature labour (in the delivery room) then another 10 minutes after; 2 STV at 10 minutes interval if extraction decision.

Choice of the time of realization of the STV = MgSO4 cross almost immediately the placental barrier after its administration.

Exclusion Criteria:

• Term of labour placement or delivery <24AW or > 35AW1day
• Absence of maternal consent
• Absence of realization of magnesium sulfate in the exposed group by maternal contraindication (Heart failure, Maternal heart rhythm disorder, Digitalis treatment, Severe hydro-electrolytic disorders, Renal insufficiency known or oligoanuria, Myasthenia, Maternal or fetal distress requiring a emergency extraction (<30min delay))
• Absence / impossibility of realization of the STV in the exposed or control group.

Exposed group( with magnesium sulfate): fetuses aged 24 + 0AW to 32 + 0AW and benefiting from MgSO4 for neuroprotective purposes, with decision of extraction or spontaneous or induced labour Control group (without magnesium sulfate) : fetuses aged 32 + 1SA to 35 + 0SA without MgSO4, with extraction decision or spontaneous or induced labour