WHO recommendation on early ultrasound in pregnancy

A pregnant woman has a basic ultrasound done by a skilled birth attendant, Haiti.

WHO recommendation on early ultrasound in pregnancy

 

Recommendation

One ultrasound scan before 24 weeks of gestation (early ultrasound) is recommended for pregnant women to estimate gestational age, improve detection of fetal anomalies and multiple pregnancies, reduce induction of labour for post-term pregnancy, and improve a woman’s pregnancy experience.

(Recommended)

 

Publication history

First published: December 2016

Updated: No update planned

Assessed as up-to-date: December 2016

 

Remarks

  • The benefits of an early ultrasound scan are not improved upon and cannot be replicated with a late ultrasound scan where there has not been an early ultrasound scan. Therefore, an ultrasound scan after 24 weeks of gestation (late ultrasound) is not recommended for pregnant women who have had an early ultrasound scan. However, stakeholders should consider offering a late ultrasound scan to pregnant women who have not had an early ultrasound scan, for the purposes of identifying the number of fetuses, presentation and placental location.
  • The GDG noted that the effects of introducing antenatal ultrasound on population health outcomes and health systems in rural, low-resource settings are unproven. However, the introduction of ultrasound to detect pregnancy complications and confirm fetal viability to the woman and her family in these settings could plausibly increase ANC service utilization and reduce morbidity and mortality, when accompanied by appropriate gestational age estimation, diagnosis, referral and management.
  • The ongoing multicountry trial that is under way should contribute further evidence on health effects, health care utilization and implementation-related information on ultrasound in rural, low-resource settings (1).
  • The GDG acknowledged that the use of early pregnancy ultrasound has not been shown to reduce perinatal mortality. The GDG put emphasis on other benefits of ultrasound (mentioned in points above) and the increased accuracy of gestational age assessment, which would assist management in case of suspected preterm birth and reduce labour induction for post-term pregnancies.
  • The GDG acknowledges that implementing and scaling up this recommendation in low-resource settings will be associated with a variety of challenges that may include political (budgeting for fees and tariffs), logistical (equipment maintenance, supplies, technical support), infrastructural (ensuring a reliable power supply and secure storage) and resources.
  • The GDG noted that antenatal ultrasound is an intervention that can potentially be task shifted from trained sonographers and doctors to trained nurses, midwives and clinical officers, provided that ongoing training, staff retention, quality improvement activities and supervision are ensured.
  • Stakeholders might be able to offset/reduce the cost of antenatal ultrasound if the ultrasound equipment is also used for other indications (e.g. obstetric emergencies) or by other medical departments.
  • The implementation and impact of this recommendation on health outcomes, facility utilization and equity should be monitored at the health service, regional and country levels, based on clearly defined criteria and indicators associated with locally agreed targets.
  • Two members of the GDG (Lisa Noguchi and Charlotte Warren) indicated that they would prefer to recommend this intervention in specific contexts with capacity to conduct close monitoring and evaluation to ensure a basic standard of implementation (including adequate capacity to diagnose and manage complications) and monitor for potential adverse effects on delivery of other critical maternal and newborn health interventions.
  • For further guidance, please refer to the WHO Manual of diagnostic ultrasound (2), available at:  
  • http://www.who.int/medical_devices/publications/manual_ultrasound_pack1-...

 

Background

Diagnostic ultrasound examination is employed in a variety of specific circumstances during pregnancy, such as where there are concerns about fetal growth and after clinical complications. However, because adverse outcomes may also occur in pregnancies without clear risk factors, assumptions have been made that antenatal ultrasound examination in all pregnancies will prove beneficial by enabling earlier detection of problems that may not be apparent (3) – such as multiple pregnancies, IUGR, congenital anomalies, malpresentation and placenta praevia – and by allowing accurate gestational age estimation, leading to timely and appropriate management of pregnancy complications.

 

Methods

The ANC recommendations are intended to inform the development of relevant health-care policies and clinical protocols. These recommendations were developed in accordance with the methods described in the WHO handbook for guideline development (4). In summary, the process included: identification of priority questions and outcomes, retrieval of evidence, assessment and synthesis of the evidence, formulation of recommendations, and planning for the implementation, dissemination, impact evaluation and updating of the guideline.

The quality of the scientific evidence underpinning the recommendations was graded using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) (5) and Confidence in the Evidence from Reviews of Qualitative research (GRADE-CERQual) (6) approaches, for quantitative and qualitative evidence, respectively. Up-to-date systematic reviews were used to prepare evidence profiles for priority questions. The DECIDE (Developing and Evaluating Communication Strategies to support Informed Decisions and Practice based on Evidence) (7) framework, an evidence-to-decision tool that includes intervention effects, values, resources, equity, acceptability and feasibility criteria, was used to guide the formulation and approval of recommendations by the Guideline Development Group (GDG) – an international group of experts assembled for the purpose of developing this guideline – at three Technical Consultations between October 2015 and March 2016.

To ensure that each recommendation is correctly understood and applied in practice, the context of all context-specific recommendations is clearly stated within each recommendation, and the contributing experts provided additional remarks where needed.

In accordance with WHO guideline development standards, these recommendations will be reviewed and updated following the identification of new evidence, with major reviews and updates at least every five years.

Further information on procedures for developing this recommendation are available here.

 

Recommendation question

For this recommendation, we aimed to answer the following question:

For pregnant women (P), does routine fetal ultrasound screening (I) in early pregnancy (before 24 weeks of gestation) or late pregnancy (after 24 weeks of gestation) compared with standard ANC (C) improve maternal and perinatal outcomes (O)?

 

Evidence summary

a) Effects of an ultrasound scan before 24 weeks of gestation (early ultrasound scan) versus selective ultrasound scan.

The evidence on early ultrasound was derived from a Cochrane review that included 11 RCTs conducted in Australia, Norway, South Africa, Sweden, the United Kingdom and the USA, involving 37 505 women (3). The intervention in all trials involved an ultrasound scan before 24 weeks of gestation, with women in the control arm undergoing selective scans if indicated (or, in one study, concealed scans, the results of which were not shared with clinicians unless requested). The scans usually included assessment of gestational age (biparietal diameter with or without head circumference and femur length), fetal anatomy, number of fetuses and location of the placenta. Scans were performed in most trials between 10 and 20 weeks of gestation, with three trials evaluating scans before 14 weeks, and three trials evaluating an intervention comprising both early (at 18–20 weeks) and late scans (at 31–33 weeks).

Maternal outcomes

Moderate-certainty evidence suggests that an early ultrasound scan probably has little or no effect on caesarean section rates (5 trials, 22 193 women; RR: 1.05; 95% CI: 0.98–1.12). However, low-certainty evidence suggests that early ultrasound may lead to a reduction in induction of labour for post-term pregnancy (8 trials, 25 516 women; RR: 0.59, 95% CI: 0.42–0.83). Regarding maternal satisfaction, low-certainty evidence suggests that fewer women may report feeling worried about their pregnancy after an early ultrasound scan (1 trial, 635 women; RR: 0.80, 95% CI: 0.65–0.99).

Fetal and neonatal outcomes

Low-certainty evidence suggests that early ultrasound scans may increase the detection of congenital anomalies (2 trials, 17 158 women; RR: 3.46, 95% CI: 1.67–7.14). However, detection rates were low for both groups (16% vs 4%, respectively) with 346/387 neonates with abnormalities (89%) being undetected by 24 weeks of gestation. Low-certainty evidence suggests that early ultrasound may make little or no difference to perinatal mortality (10 trials, 35 737 births; RR: 0.89, 95% CI: 0.70–1.12) and low birth weight (4 trials, 15 868 neonates; RR: 1.04, 95% CI: 0.82–1.33). Moderate-certainty evidence also shows that it probably has little or no effect on SGA (3 trials, 17 105 neonates; RR: 1.05, 95% CI: 0.81–1.35).

 

b) Effects of an ultrasound scan after 24 weeks of gestation (late ultrasound scan) versus no late ultrasound scan

This evidence on late ultrasound was derived from a Cochrane review that included 13 RCTs conducted in HICs (8). Most women in these trials underwent early ultrasound scan and were randomized to receive an additional third trimester scan or to selective or concealed ultrasound scan. The purpose of the late scan in these trials, which was usually performed between 30 and 36 weeks of gestation, variably included assessment of fetal anatomy, estimated weight, amniotic fluid volume and/or placental maturity.

Maternal outcomes

Moderate-certainty evidence suggests that a late ultrasound scan probably has little or no effect on caesarean section (6 trials, 22 663 women; RR: 1.03, 95% CI: 0.92–1.15), instrumental delivery (5 trials, 12 310 women; RR: 1.05, 95% CI: 0.95–1.16) and induction of labour (6 trials, 22 663 women; RR: 0.93; 95% CI: 0.81–1.07). Maternal satisfaction was not assessed in this review.

Fetal and neonatal outcomes

Moderate-certainty evidence suggests that a late ultrasound scan probably has little or no effect on perinatal mortality (8 trials, 30 675 births; RR: 1.01, 95% CI: 0.67–1.54) and preterm birth (2 trials, 17 151 neonates; RR: 0.96, 95% CI: 0.85–1.08).  Low certainty evidence suggests that it may have little or no effect on SGA (4 trials, 20 293 neonates; RR: 0.98, 95% CI: 0.74–1.28) and low birth weight (3 trials, 4510 neonates; RR: 0.92, 95% CI: 0.71–1.18).

 

Additional considerations

The evidence on ultrasound is derived mainly from HICs, where early ultrasound is a standard component of ANC to establish an accurate gestational age and identify pregnancy complications. The impact of ultrasound screening in low-resource settings is currently unknown but the low rates of maternal and perinatal mortality experienced in HICs indirectly suggests that ultrasound is an important component of quality ANC services. Evidence from the Cochrane review on early ultrasound suggests that multiple pregnancies may be less likely to be missed/undetected by 24–26 weeks of gestation with early ultrasound (3). Of 295 multiple pregnancies occurring in seven trials (approximately 24 000 trial participants), 1% (2/153) were undetected by 24–26 weeks of gestation with early ultrasound screening compared with 39% (56/142) in the control group (RR: 0.07, 95% CI: 0.03–0.17; graded by review authors as low-quality evidence). The Cochrane review also evaluated several safety outcomes in offspring and found no evidence of differences in school performance, vision and hearing, disabilities or dyslexia.

An ongoing multicountry cluster RCT of antenatal ultrasound in the Democratic Republic of the Congo, Guatemala, Kenya, Pakistan and Zambia should contribute data on health outcomes and health care utilization, as well as implementation related information on ultrasound in rural, low resource settings (1). The trial intervention involves a two-week obstetric ultrasound training course for health workers (e.g. midwives, nurses, clinical officers) to perform ultrasound scans at 18–22 weeks and 32–36 weeks of gestation in each participant enrolled.

Accurate gestational age dating is critical for the appropriate delivery of time-sensitive interventions in pregnancy, as well as management of pregnancy complications, particularly pre-eclampsia and preterm birth, which are major causes of maternal and perinatal morbidity and mortality in LMICs, and early ultrasound is useful for this purpose.

Resources

The cost of ultrasound equipment, especially portable compact units, has decreased (9), and they are currently available at less than US$ 10 000 (10). Thus, given the cost of equipment, maintenance, supplies (ultrasound gel), replacement batteries, initial and ongoing staff training and supervision, and staffing costs (allowing 15–45 minutes per scan), routine ultrasound scans may have considerable resource implications for LMIC settings.

Equity

Effective interventions to increase uptake and quality of ANC services, and improve the experience of care, are needed in LMICs to prevent maternal and perinatal mortality and improve equity. However, if women are expected to pay for ultrasound scans, or if scans are not available to women living in rural areas due to feasibility issues, this intervention could perpetuate inequalities. In addition, ultrasound sexing of the fetus in some low-income countries has a negative impact on gender equity and needs to be monitored.

Further information and considerations related to this recommendation can be found in the WHO guidelines, available at:

http://apps.who.int/iris/bitstream/10665/250796/8/9789241549912-websupplement-eng.pdf?ua=1

 

 

Implementation considerations

  • The successful introduction of evidence-based policies related to antenatal care into national programmes and health care services depends on well-planned and participatory consensus-driven processes of adaptation and implementation. These processes may include the development or revision of national guidelines or protocols based on this recommendation.
  • The recommendation should be adapted into locally-appropriate documents and tools that are able to meet the specific needs of each country and health service. Modifications to the recommendation, where necessary, should be justified in an explicit and transparent manner.
  • An enabling environment should be created for the use of this recommendation, including changes in the behaviour of health care practitioners to enable the use of evidence-based practices.
  • Local professional societies may play important roles in this process and an all-inclusive and participatory process should be encouraged.
  • Antenatal care models with a minimum of eight contacts are recommended to reduce perinatal mortality and improve women’s experience of care. Taking this as a foundation, the GDG reviewed how ANC should be delivered in terms of both the timing and content of each of the ANC contacts, and arrived at a new model – the 2016 WHO ANC model – which replaces the previous four-visit focused ANC (FANC) model. For the purpose of developing this new ANC model, the ANC recommendations were mapped to the eight contacts based on the evidence supporting each recommendation and the optimal timing of delivery of the recommended interventions to achieve maximal impact.

 

Research implications

The GDG did not identify any priority question related to this recommendation

 

WHO recommendations on antenatal care for a positive pregnancy experience: ultrasound examination.  Highlights and key messages from World Health Organization’s 2016 global recommendations (January 2018)

 

Related links

WHO recommendations on antenatal care for a positive pregnancy experience

(2016) - full document and evidence tables

Managing Complications in Pregnancy and Childbirth: A guide for midwives and doctors

Pregnancy, Childbirth, Postpartum and Newborn Care: A guide for essential practice

WHO Programmes: Sexual and Reproductive health

Maternal Health

 

 

References

  1. McClure EM, Nathan RO, Saleem S, Esamai F, Garces A, Chomba E et al. First look: a clusterrandomized trial of ultrasound to improve pregnancy outcomes in low income country settings. BMC Pregnancy Childbirth. 2014;14:73. doi:10.1186/1471-2393-14-73.
  2. Manual of diagnostic ultrasound, second edition. Geneva: World Health Organization; 2013 (http://www.who.int/medical_devices/ publications/manual_ultrasound_pack1-2/en/, accessed 26 October 2016)
  3. Whitworth M, Bricker L, Mullan C. Ultrasound for fetal assessment in early pregnancy. Cochrane Database Syst Rev. 2015;(7):CD007058
  4. WHO handbook for guideline development, 2nd edition. Geneva: World Health Organization; 2014 (http://www.who.int/kms/handbook_2nd_ ed.pdf, accessed 6 October 2016).
  5. GRADE [website]. The GRADE Working Group; 2016 (http://gradeworkinggroup.org/, accessed 27 October 2016).
  6. GRADE-CERQual [website]. The GRADECERQual Project Group; 2016 (https://cerqual. org/, accessed 27 October 2016).
  7. The DECIDE Project; 2016 (http://www.decide-collaboration.eu/, accessed 27 October 2016).
  8. Bricker L, Medley N, Pratt JJ. Routine ultrasound in late pregnancy (after 24 weeks’ gestation). Cochrane Database Syst Rev. 2015;(6):CD001451.
  9. Harris RD, Marks WM. Compact ultrasound for improving maternal and perinatal care in low-resource settings. J Ultrasound Med. 2009. 28(8):1067–76.
  10. WHO compendium of innovative health technologies for low-resource settings, 2011–2014: assistive devices, eHealth solutions, medical devices, other technologies, References 125 technologies for outbreaks. Geneva: World Health Organization; 2015 (http://www.who.int/ medical_devices/innovation/compendium/en/, accessed 26 September 2016).

 

Citation: WHO Reproductive Health Library. WHO recommendation on early ultrasound in pregnancy. (December 2016). The WHO Reproductive Health Library; Geneva: World Health Organization.