Effect of magnesium sulphate on fetal heart rate parameters: a systematic review.

OBJECTIVE

To examine the potential effects of intravenous magnesium sulphate (MgSO4) administration on antepartum and intrapartum fetal heart rate (FHR) parameters measured by cardiotocography (CTG) or electronic fetal monitoring (EFM).

METHODS

We undertook a systematic review of randomized controlled trials, observational studies, and case series. Studies were reviewed independently by two reviewers and qualitatively analyzed with regard to CTG/EFM parameters (baseline FHR, variability and acceleration-deceleration patterns), types of participants, interventions offered, and outcomes reported.

RESULTS

Of 18 included studies, two were RCTs (72 women); 12 were prospective observational studies (269 women), 10 of which were of a pre- and post-intervention design; one was a prospective cohort study (36 women) and three were retrospective cohort studies (555 women). Lower baseline FHR was associated with MgSO4 exposure in seven of nine relevant studies. Decreased FHR variability was reported in nine of 12 relevant studies. Reductions in reactivity or acceleration pattern were seen in four of six relevant studies without an increase in decelerative patterns. All changes were small and not associated with adverse clinical outcomes.

CONCLUSION

Maternal administration of MgSO4 for eclampsia prophylaxis/treatment, tocolysis or fetal neuroprotection appears to have a small negative effect on FHR, variability, and accelerative pattern, but is not sufficient clinically to warrant medical intervention.