Routine third-trimester ultrasound in low-risk pregnancies and perinatal death: a systematic review and meta-analysis

Abstract

This study aimed to determine whether routine third-trimester ultrasounds in low-risk pregnancies decrease the rate of perinatal death compared with regular antenatal care with serial fundal height measurements. DATA SOURCES: This was a systematic review and meta-analysis of randomized control trials to identify relevant studies published from inception to October 2019. The databases used were Ovid, PubMed, Scopus, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials using a combination of key words related to "third trimester ultrasound" and "low-risk." STUDY ELIGIBILITY CRITERIA: We included all randomized control trials of singleton, nonanomalous low-risk pregnancies that were randomized to either one or more thirdtrimester ultrasounds (ultrasound group) or serial fundal height (fundal height group). Exclusion criteria were patients with multiple gestations, maternal medical complications, or fetal abnormalities requiring a third-trimester ultrasound. STUDY APPRAISAL AND SYNTHESIS METHODS: The primary outcome was the rate of perinatal death. The secondary outcomes were rates of fetal growth restriction, suspected large for gestational age, polyhydramnios, oligohydramnios, fetal anomalies, antenatal interventions, stillbirth, neonatal death, cesarean delivery, induction of labor, and other neonatal outcomes. This meta-analysis was performed with the use of the random effects model of DerSimonian and Laird to produce relative risk or mean difference with a corresponding 95% confidence interval. RESULTS: A total of 7 randomized control trials with 23,643 participants (12,343 in the ultrasound group vs 11,300 in the fundal height group) were included. The total rate of perinatal death was similar among the groups (41 of 11,322 [0.4%] vs 34 of 10,285 [0.3%]; relative risk, 1.14; 95% confidence interval, 0.68e1.89). The rate of fetal growth restriction was higher in the ultrasound group (763 of 10,388 [7%] vs 337 of 9021 [4%]; relative risk, 2.11; 95% confidence interval, 1.86e2.39) and the rate of suspected large for gestational age (1060 of 3513 [30%] vs 375 of 3558 [11%]; relative risk, 2.84; 95% confidence interval, 2.6e3.2). Polyhydramnios was also significantly higher in the ultrasound group than the fundal height group (18 of 323 [6%] vs 4 of 322 [1%] relative risk, 3.93; 95% confidence interval, 1.4e11). The rates of the remainder of the secondary outcomes were similar among the groups. CONCLUSION: Routine third-trimester ultrasounds do not decrease the rate of perinatal death compared with serial fundal height in low-risk pregnancies. Ideally, an adequately powered trial is warranted to determine whether perinatal mortality in the fundal height group can be reduced by one-third with third-trimester ultrasound.

ISUOG Practice Guidelines: performance of third‐trimester obstetric ultrasound scan

“…They found that the rate of identification of LGA was higher in the routine ultrasound group (30%) compared with that in the serial SFH measurement group (11%), although there was no significant difference in the incidence of LGA at birth (9% in both groups). The same meta‐analysis did not find a significant difference in perinatal mortality rate between the two groups (ultrasound group, 0.4% vs SFH group, 0.3% (relative risk (RR), 1.14; 95% CI, 0.68–1.89)) 56 . Nor were there any significant differences between the two groups in terms of the rates of stillbirth or neonatal death.…”

“…Al-Hafez et al 56 , in a systematic review including seven RCTs and 23 643 women, compared detection of LGA (EFW > 90 th centile) by routine ultrasound examination with that by serial measurements of the symphysis-fundus height (SFH). They found that the rate of identification of LGA was higher in the routine ultrasound group (30%) compared with that in the serial SFH measurement group (11%), although there was no significant difference in the incidence of LGA at birth (9% in both groups).…”

Re‐Evaluation of Fetal Anatomy During Third Trimester Follow‐Up Ultrasound Examination

“…We are not advocating a routine third trimester ultrasound for every obstetrical patient. Recent trials have shown that routine third-trimester ultrasound in low-risk patients can increase the detection of small-for-gestational age fetuses, 7,8 but these trials and several meta-analyses [7][8][9][10][11] have concluded that a routine third trimester exam in low-risk patients does not reduce perinatal death or improve other perinatal outcomes. Indeed, ultrasound diagnosis of large-for-gestational-age may unnecessarily increase the rate of cesarean birth.…”

The impact of a universal late third‐trimester scan for fetal growth restriction on perinatal outcomes in term singleton births: A prospective cohort study

“…6 Given the limited predictive value of these risk factors and the potential for human error 2 and concerns regarding equity, 'universal' ultrasound has been explored. 7,8 Evidence suggests this increases the detection rate of birthweight (<10th centile) 7,8 but does not improve perinatal outcomes, 8,9 not least because many SGA babies are not growth-restricted 10,11 and birthweight (<10th centile) constitute less than a quarter of stillbirths. 3 Nevertheless, impaired placental function may be present in about half of stillbirths, 12 and the concept of fetal growth restriction (FGR) has developed.…”