Official guidelines do not recommend or recommend against routine late pregnancy ultrasounds in low-risk pregnancies. Instead, they recommend reserving them for pregnancies with specific medical indications.

Routine ultrasound screening has not been shown to improve important maternal or perinatal outcomes compared with selective ultrasounds performed only for clinical indications in healthy, low-risk pregnancies.

Randomized trials have not consistently demonstrated an increase in induction or cesarean birth. However, trials and or observational studies do show that increased detection of suspected abnormalities or fetal concerns (like IUGR or big baby) is associated with increased inductions, cesareans and NICU admittance without demonstrating an improvement to neonatal outcomes.

A single ultrasound suggesting a baby is “small” or “large” should not be interpreted in isolation when decisions about induction of labor or cesarean birth are being considered.

Ultrasounds are a valuable tool (when indicated) in late pregnancy for seeking to evaluate things like suspected IUGR, breech babies or placental location, although are acknowledged to be imprecise, especially in weight estimation.

Routine Third Trimester Ultrasounds
Ultrasound examinations performed during the third trimester as routine screening in pregnancies without a specific medical concern or indication (BRICKER ET AL., 2015; ACOG, 2017B).

Medically Indicated Ultrasounds
An ultrasound performed to answer a specific clinical question or evaluate a suspected problem, rather than as routine screening (ACOG, 2017A; ACOG, 2017B). Examples include suspected fetal growth restriction, breech presentation, and placental concerns. (ACOG, 2021A; ACOG, 2021B; ACOG, 2019; ACOG, N.D.).

Fundal Height
The distance from the pubic bone to the top of the uterus, measured during prenatal visits. Fundal height measurements are used to screen a baby’s size and growth during pregnancy (ACOG, 2025A; ACOG, 2025B).

Fetal Macrosomia (LGA or Large for Gestational Age)
A term used to describe a baby with an unusually high birth weight, regardless of gestational age (ACOG, 2020).

Fetal Growth Restriction (IUGR, IGR or FGR)
A baby who is measuring smaller than expected for gestational age and it is suspected that the baby is not fulfilling its growth potential because of an underlying pathological condition (ACOG, 2021A; SMFM, 2020).

SGA (Small for Gestational Age)
A baby born weighing below the 10th percentile for their gestational age; SGA describes the baby’s size and does not necessarily mean that growth was pathologically restricted (ACOG, 2021; RCOG, 2024).

(ACOG, 2016; ACOG, 2017A; ACOG, 2017B; ACOG, 2019; ACOG, 2021A; ACOG, 2021B; ACOG, N.D.; BRICKER ET AL., 2015)

Both the American College of Obstetricians and Gynecologists (ACOG) and the World Health Organization (WHO) do not recommend or recommend against routinely performing third-trimester ultrasounds in uncomplicated pregnancies because current evidence has not shown that this practice improves maternal or fetal outcomes (ACOG, 2016; BRICKER ET AL., 2015; WHO, 2016).

Instead, ultrasounds after the anatomy scan, should be reserved for pregnancies with a specific medical indication, such as suspected fetal growth restriction, abnormal fundal-height measurements, maternal medical conditions, abnormal fetal presentation, or other clinical concerns (ACOG, 2016). This recommendation is based on randomized trials and systematic reviews (BRICKER ET AL., 2015). At the same time, ACOG notes that routine screening increases the detection of suspected abnormalities, which can lead to additional surveillance, labor induction, and cesarean birth without clear evidence of benefit (ACOG, 2016). Because of these considerations, ACOG recommends a selective, indication-based approach rather than universal routine screening (ACOG, 2016; ACOG, 2017A).

“Ultrasonography... should be used prudently and only when use is expected to answer a relevant clinical question or otherwise provide medical benefit to the patient” (ACOG, 2017A).

This systematic review and meta-analysis included 13 randomized controlled trials involving 34,980 women and compared routine ultrasound after 24 weeks with ultrasound performed only for clinical indications. It evaluated whether routine scanning improved neonatal outcomes or affected intervention rates (BRICKER ET AL., 2015).

Routine late ultrasound did not reduce perinatal mortality or preterm birth or demonstrate an overall benefit for mothers or babies. Pooled trials found no statistically significant overall differences in induction or cesarean birth, although induction rates varied considerably between studies—an important contextual concern (BRICKER ET AL., 2015).

This trial was a large randomized controlled trial conducted to analyze routine obstetric ultrasounds. The study included 15,151 low-risk pregnant women from 109 U.S. practices. Women were randomly assigned to receive routine ultrasound examinations at 15–22 weeks and again at 31–35 weeks, or to receive ultrasounds only when there was a medical indication (EWIGMAN ET AL., 1993).

Routine third-trimester ultrasound detected additional fetal abnormalities but did not reduce perinatal mortality or serious neonatal illness or improve overall pregnancy outcomes compared with selective ultrasound for clinical indications. This landmark trial was later included in the 2015 Cochrane review and helped inform ACOG guidance for low-risk pregnancies (EWIGMAN ET AL., 1993; BRICKER ET AL., 2015; ACOG, 2016).

Author’s contextual analysis: Care provided within a clinical trial may differ from routine care because trial clinicians are aware that outcomes are being observed. Practices also vary in their guidelines and rates of induction and planned cesarean, as seen in the trials included in this review. Families should therefore consider that these pooled results may not translate directly to every real-world clinical setting.

Late pregnancy ultrasound can estimate fetal weight, but it cannot determine a baby's actual birth weight. Even when performed correctly, ultrasound estimates become less accurate as pregnancy advances, particularly at the very end. Because of this uncertainty, some babies suspected to be "too large" are ultimately born at an average weight, while some truly large babies are underestimated. This is reflected in the trials & studies below.

"The diagnosis of fetal macrosomia is imprecise. For suspected fetal macrosomia, the accuracy of estimated fetal weight using ultrasound biometry is no better than that obtained with abdominal palpation." (ACOG, 2020)

This retrospective cohort study examined 21,743 singleton births following routine ultrasound at 35–37 weeks. Ultrasound identified only approximately 35% of babies ultimately born large for gestational age. Among LGA babies, those identified large before birth underwent more inductions and cesareans without a demonstrated improvement in neonatal outcomes. Identified babies born large were slightly larger than babies born large but not prenatally identified. Babies born large & prenatally identified also did show increased rates of shoulder dystocia, however the study lacked sufficient contextual information to determine whether the higher shoulder-dystocia rate was due to higher birth weight, other labor interventions, or potential over classification of shoulder dystocia’s for larger babies with a slower head-to-body interval. The trial does not distinguish exact outcomes for babies with shoulder dystocia, but the identified group with more dystocia’s, as mentioned, did not show worse neonatal outcomes.

Authors contextual bias note on Lopain: This observational study did not report how the shoulder dystocia’s were defined, therefore this leaves room subjective results & not accurate statical conclusions.

This open-label randomized controlled trial assigned 2,893 women with an ultrasound-suspected large for gestational age baby to induction at 38+0–38+4 weeks or standard care (induction only with indication). The primary analysis found that induction did not significantly reduce shoulder dystocia (2.3% vs 3.1%). Researchers suggested that this result may have been diluted because many standard-care participants delivered earlier than anticipated, narrowing the intended timing difference between groups.

A secondary analysis of trial data looked specifically at participants who followed the intended timing gap (were not induced before 38+4) and did find fewer cases of shoulder dystocia with induction (2.3% vs 3.7%). However, there was no improvement in birth injury or other neonatal outcomes was between these groups. Approximately 60% of babies suspected to be LGA (large for gestational age) were not LGA at birth. The trial ended before reaching its planned enrollment because shoulder dystocia occurred less frequently than anticipated and many standard-care participants delivered earlier than expected.

This Trial has received widespread critique over the criteria used to claim a shoulder dystocia. Some critics have claimed that the trial used RCOG’s criteria which allows for a head to body interval less than 60 seconds to be classified as a dystocia, this is not accurate. This trial does list a head to body interval greater than 60 seconds as a secondary reasoning, however this must be accompanied by failure of gentle traction and the need for maneuvers for babies’ extraction as the primary reasoning. However, the criteria and the trial results do not state how long the clinicians waited before administering assistance via maneuvers. It also does not state whether there were clear signs of a shoulder dystocia present before action was taken. For a large baby, it would not be uncommon for a mother to need a secondary, fresh contraction after the head is born, to be able to gain the strength to push out a larger circumference body. This is a very important evidence-quality consideration for the following reasons:

If fundal-height measurement suggests that a baby may be small, ACOG recommends ultrasound assessment. An estimated fetal weight or abdominal circumference below the 10th percentile meets ACOG’s definition of fetal growth restriction, but does not automatically require induction. Further surveillance, umbilical-artery Doppler assessment, and sometimes serial growth scans help distinguish a constitutionally small baby from pathological growth restriction and guide delivery timing (ACOG, 2021A; ACOG, 2025B).

“An additional challenge is the difficulty in differentiating between the fetus that is constitutionally small and fulfilling its growth potential and the small fetus that is not fulfilling its growth potential because of an underlying pathologic condition” (ACOG, 2021A).

This population-based study examined 14,100 singleton births. Whether or not babies were ultimately born small for gestational age, those suspected of fetal growth restriction before birth were at least approximately four times as likely to be born preterm, require resuscitation, or be admitted to a neonatal unit. Most additional preterm births followed induction or planned cesarean birth. Because this was observational, it cannot prove that the diagnosis caused these outcomes (MONIER ET AL., 2015).

This Dutch trial included 13,046 low-risk pregnancies recruited through 60 midwifery practices. Two routine growth scans increased prenatal detection of babies ultimately born small for gestational age from 19% to 32%, but also increased false-positive suspicion from 3.1% to 10.2%. Induction increased from 13.7% to 15.9%, while severe perinatal outcomes remained similar at 1.8% versus 1.7%. The routine-scan group averaged 2.04 third-trimester scans compared with 0.88 under usual care, meaning usual care did not represent “no ultrasound.” The trial was pragmatic and unblinded (HENRICHS ET AL., 2019).

There is currently little to no high-quality evidence that increasing prenatal detection of small babies through routine ultrasound improves severe neonatal outcomes. Some smaller trials may demonstrate lower NICU rates with additional scans, but neonatal outcomes were ultimately not improved. However, due to size & bias potential these trials are not considered high-quality evidence. There was a small Portuguese trial that indicated doppler ultrasounds evaluating specific things compared to growth scans checking size, may improve outcomes (RATIO37 STUDY GROUP, 2024). However, more research is needed.

Ultrasound estimates of fetal weight have a recognized margin of error, with errors greater than 10% occurring in some studies (MILNER & AREZINA, 2018).

Author’s consideration: This uncertainty is relevant when weighing the potential benefits and risks of interventions based on estimated fetal size.

In a randomized trial of 2,834 singleton pregnancies, five scheduled examinations combining ultrasound imaging and continuous-wave Doppler, performed between 18 and 38 weeks, were associated with a 35% relative increase in birthweight below the 10th percentile compared with a single imaging ultrasound at 18 weeks. Because the intensive protocol combined imaging and Doppler, the trial cannot determine whether either component—or their repeated combination—accounted for the finding. The authors acknowledged chance could be a possible explanation. The trial therefore presents a safety signal concerning repeated combined exposure; however, it does not prove that routine obstetric ultrasound causes fetal growth restriction (NEWNHAM ET AL., 1993).

(DPVSA, 2024; GOI, N.D.; OUH, 2025)

Note. All three countries are among those with the world’s lowest neonatal mortality rates. Their outcomes do not prove that fewer ultrasounds are better, but they demonstrate that excellent neonatal outcomes can be achieved without universal third-trimester ultrasound screening (UN IGME, 2026).

Authors Contextual Comparison: In these publicly governed Nordic healthcare systems, national ultrasound recommendations function as part of the routine maternity-care pathway. In the United States, guidance issued by professional organizations such as ACOG informs care but is voluntary and may be interpreted differently by individual physicians, practices and hospital systems.