Timing of serial ultrasound in at risk pregnancies: A randomized controlled trial (sun trial)

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Conference Proceeding

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Am J Obstet Gynecol


OBJECTIVE: Pregnancies with several complications are at risk for abnormalities of fetal growth or of amniotic fluid (AF) and are at risk of adverse neonatal outcomes. To detect these abnormalities, serial 3rd trimester ultrasound examinations (USE) are recommend every 2 to 4 weeks (ACOG Practice Bulletin Ultrasound in Pregnancy 2016). We hypothesized that among at risk pregnancies, USE every 2 weeks will have higher detection rates of abnormal growth or of AF abnormalities than USE every 4 weeks. STUDY DESIGN: Women with singleton pregnancies complicated by various medical comorbidities at 24-28 weeks were randomized (NCT02719886) to USE every 2 versus every 4 weeks. The primary outcome was findings of fetal growth restriction (FGR), large for gestational age (LGA), oligo-or poly-hydramnios. A total of 228 participants were needed to detect a 30% difference in detection of fetal growth or AF abnormalities between groups (baseline 58%; alpha = 0.05, power=0.8). RESULTS: All randomized women (N=112 to every 2 weeks; N=116 to every 4 weeks) were included in the intent to treat analysis. The primary outcome was similar amongst USE groups every 2 vs 4 weeks (41% vs 38%; RR 1.11; 95% CI 0.78-1.58). The following also occurred with similar frequency between groups: admission and/or delivery related to abnormal USE findings (12% vs 18%; P=0.53); cesarean delivery (41% vs 39%; P=0.78) and pre-specified composite maternal and neonatal morbidity (Table 1). The predictive accuracy of detecting small for gestational age was similar with USE every 2 vs 4 weeks (positive likelihood ratio of 7.3 and 8.3, respectively). Detection of large for gestational age was also similar with the two schema: LR (+) of 5.6 with USE every 2 weeks and 9.2 with every 4 weeks (Table 2). CONCLUSION: In at risk pregnancies, serial ultrasound examinations every 2 weeks as compared to every 4 weeks did not improve the detection of abnormal fetal growth or of amniotic fluid.





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