Tocolytics are potent drugs that are used to interdict preterm labour. Although all of these agents have some side effects, if not frankly adverse effects under certain clinical situations, two of these drugs, the beta-mimetics and magnesium sulphate (MgSO(4)), have been found to have considerable potential for adverse maternal cardiovascular and respiratory effects. Furthermore, magnesium sulphate has been shown to have harmful, indeed, sometimes lethal, effects in some babies. Although less well established, NSAIDs, the most common example of which is indomethacin, also have some important adverse effects in fetuses. Within the limits of contemporary scientific knowledge, calcium channel blockers, such as nifedipine, appear to be among the more efficacious and safer drugs that are currently being used for tocolysis.
Objectives
The purpose of this study was to compare Doppler velocimetric indices between the left and right intra‐abdominal umbilical arteries in normally grown and growth‐restricted fetuses.
Methods
In this cross‐sectional study, Doppler indices of the intra‐abdominal segment of the left and right umbilical arteries were measured lateral to the fetal bladder. Measurements, including the systolic to diastolic ratio and pulsatility index, were obtained from both anatomic locations. The Student t test was used to make comparisons.
Results
Differences between left and right Doppler indices were noted in 98% of patients, and these differences were greater than 20% in at least one‐third. Overall, the left umbilical artery had a higher systolic to diastolic ratio (P = .025) and pulsatility index (P = .007) than the right umbilical artery.
Conclusions
The laterality of the umbilical artery, whether on the left or right side of the fetus, influences important Doppler blood flow parameters.
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