The effects of ritodrine and magnesium sulfate on maternal and fetal Doppler blood flow patterns in women with preterm labor

Objective

To determine the effects of ritodrine and magnesium sulfate on maternal-fetal blood flows.

Study design

A total of 85 pregnant women between 26th and 36th weeks with preterm labor, and 83 healthy pregnant women were included. Patients in the study group were randomly assigned to receive either ritodrine (with the addition of verapamil) (n = 46) or magnesium sulfate (n = 39). Blood flow examinations on the umbilical artery (UA), middle cerebral artery (MCA), bilateral uterine arteries (Ut.A) and ductus venosus (DV) were performed before and 48 h after initiating therapy.

Results

UA pulsatility index (PI) significantly differed in women receiving tocolysis compared to controls after 48 h. DV PI increased in women receiving MgSO₄, whereas it decreased in the ritodrine and control groups. Ut.A values did not significantly change after 48 h in the groups.In women between the 26th and 32nd weeks, UA, MCA and DV PI did not significantly change after 48 h in the three groups. However, in women between the 32nd and 36th weeks UA and MCA PI significantly differed in the treatment groups compared to controls after 48 h. DV PI increased in women receiving MgSO₄, whereas it decreased in the ritodrine and control groups.

Conclusions

MgSO₄ and ritodrine affect blood flow patterns after 48 h in some maternal-fetal vessels. These effects on blood flow are particularly significant in women between 32nd and 36th weeks. The effects of both drugs on fetal and maternal Doppler flows seem similar, except the increased resistance to flow in DV in women receiving MgSO₄.