Clinical Practice Guidelines Antenatal Care — Module II
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- Fetal development and anatomy
- Congenital anomalies in Australia
- Offering assessment of fetal development and anatomy
- Accuracy and effectiveness of ultrasound assessment of fetal development and anatomy
- Timing of ultrasound assessment of fetal development and anatomy
- Who should conduct the assessment
- Discussing assessment of fetal development and anatomy
- Practice summary: fetal development and anatomy
6Clinical assessmentsA range of clinical assessments is offered to promote and enhance the physical and emotional wellbeing of a woman and her baby during pregnancy. This chapter discusses assessments that are offered to all women during pregnancy. Recommendations are based on evidence about the accuracy of assessments in predicting complications in pregnancy and the effectiveness of interventions in reducing symptoms. Table 6 presents a summary of advice on assessments during pregnancy considered a priority for inclusion in these Guidelines. Advice on other assessments, such as routine breast and pelvic examination (which are not recommended) is included in the NICE Guidelines (NICE 2008). Table 6 : Summary of advice for women about assessments during pregnancy
Ultrasound examination between 18 and 20 weeks gestation allows assessment of fetal development and anatomy. It is also used to estimate gestational age when this has not been assessed in the first trimester. BackgroundDiagnostic ultrasound is a sophisticated electronic technology that uses pulses of high frequency sound to produce an image. This imaging can enable measurement of the baby, estimation of the gestational age and identification of structural anomalies. Gestational age assessment and screening for chromosomal anomalies in the first trimester are discussed in Module I of the Guidelines. This section discusses the second trimester scan to assess the development and anatomy of the baby and the position of the placenta. This assessment is also known as the morphology scan. Congenital anomalies in AustraliaIn Australia in 2010, congenital anomalies (including chromosomal and structural anomalies) was the leading cause of perinatal death in single pregnancies (28.8%) and accounted for 76.1% of neonatal deaths of babies born at 32–36 weeks gestation and 44.1% of deaths of babies born after 37 weeks gestation (Li et al 2012). Available data on neural tube defects among babies born to Aboriginal and Torres Strait Islander women show a higher overall prevalence than among non-Indigenous women (16.6 versus 7.3 per 10,000 total births in 2006–2008) (AIHW 2011). Offering assessment of fetal development and anatomySummary of the evidenceRoutinely offering women an ultrasound during the second trimester to screen for fetal anomalies and location of the placenta is recommended in the United Kingdom (NICE 2008), the United States (ACOG 2009) and Canada (Cargill et al 2009) and has been previously recommended in Australia (RANZCOG 2009). Although cervical length is increasingly reported, there is insufficient evidence to recommend its routine assessment (RANZCOG 2008; 3 Centres Collaboration 2012). Accuracy and effectiveness of ultrasound assessment of fetal development and anatomyGestational age: While gestational age assessment using ultrasound is more accurate in the first trimester (Kalish et al 2004; Caughey et al 2008), some women may not have access to ultrasound until later in pregnancy. Gestational age has been successfully estimated in the second trimester (Johnsen et al 2005; Oleson & Thomsen 2006). Structural anomalies: Ultrasound has been used in the second trimester to detect anomalies of the heart (Perri et al 2005; Del Bianco et al 2006; Westin et al 2006; Fadda et al 2009), renal tract (Cho et al 2005) and umbilical artery (Cristina et al 2005), neural tube defects (Norem et al 2005) and anomalies resulting from exposure to alcohol (Kfir et al 2009). The rate of detection of structural anomalies is generally higher in the second than in the first trimester (Saltvedt et al 2006; Hildebrand et al 2010). “Soft” markers: While the combination of nuchal thickness and biochemical markers in the first trimester is more effective in identifying chromosomal anomalies (see Module I, Chapter 9), some markers (eg echogenic bowel, short femur, short humerus, thickened nuchal fold, absent nasal bone) identified in the second trimester ultrasound occur more frequently in babies with chromosomal anomalies (Bottalico et al 2009). A combination of markers is more accurate than a single marker alone; for example only 5% of babies with identified chromosomal anomalies had echogenic bowel as the only finding (Iruretagoyena et al 2010). Placenta: Second trimester ultrasound has effectively identified placental location (Cargill et al 2009), overlap of the cervical os (Robinson et al 2012), placental length (which may assist in identifying risk of having a small-for-gestational age baby) (McGinty et al 2012) and placenta praevia (which may resolve in women with [61%] and without [90%] a previous caesarean section) (Lal et al 2012). Type of ultrasonography: Accurate assessment can be performed using standard 2D ultrasonography. Assessment may be performed more rapidly using 3D ultrasonography (Benacerraf et al 2006; Pilu et al 2006). Timing of ultrasound assessment of fetal development and anatomyRecommended timing of the ultrasound scan varies in international guidelines but is generally in the range of 18–20 weeks as: sensitivity in detecting structural anomalies increases after 18 weeks gestation (Cargill et al 2009); and detection of structural anomalies before 20 weeks gestation gives women the choice of terminating the pregnancy, where this is permitted under jurisdictional legislation. Ultrasound can be used to assess gestational age up to 24 weeks gestation and to detect anomalies throughout the pregnancy. Recommendation 11 Grade B Offer pregnant women ultrasound screening to assess fetal development and anatomy between 18 and 20 weeks gestation. Practice point l Timing of the ultrasound will be guided by the individual situation (eg for women who are obese, visualisation may improve with gestational age). There is no benefit from repeated diagnostic ultrasound assessments unless clinically indicated. Repeated tests may increase costs for women, be inconvenient and have the potential to increase anxiety (eg through false positives). As well, access for some women is limited as this technology is not available in all settings.
Repeated ultrasound assessment may be appropriate for specific indications but should not be used for routine monitoring. Other considerationsBenefits and harmsA Cochrane review (Whitworth et al 2010) found a reduced number of inductions for ‘prolonged pregnancy’ and no significant differences in birth weight, size for gestational age, Apgar scores and rates of admission to neonatal intensive care between babies exposed to ultrasound in early pregnancy (before 24 weeks) and those not exposed. There were no significant differences in growth and development, visual acuity or hearing for children aged 8–9 years (Whitworth et al 2010). Follow-up at 15–16 years (n=4,458) found no significant effect on overall school performance (Stalberg et al 2009). No studies were identified that assessed psychological benefits or harms to the mother. Women may not be fully informed about the purpose of routine ultrasound and may be made anxious, or be inappropriately reassured by scans (Garcia et al 2002; Lalor & Devane 2007). A small systematic review found insufficient evidence to support either high or low levels of feedback during ultrasound to reduce maternal anxiety and change maternal health behaviour (smoking, alcohol use) (Nabhan & Faris 2010). Who should conduct the assessment?Minimum standards for health professionals conducting ultrasound assessments are disseminated by the Australian Society for Ultrasound in Medicine, the Australasian Sonographer Accreditation Registry, the Australian Sonographers Association, the Royal Australian and New Zealand College of Radiologists, and the Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Practice point n Ultrasound assessment should only be performed by healthcare professionals with appropriate training and qualifications, within the appropriate scope (eg diagnostic or point of care). Access to ultrasoundThe costs associated with ultrasound may limit access for some women, particularly if bulk-billed services are not available in their area. In remote regions, it may be difficult for women to access ultrasound examination due to limited availability of appropriate equipment, a lack of accredited and trained professionals in some areas and the costs involved in travelling for the assessment. It is noted that there is a lack of consistency in funding across the States and Territories to support travel and accommodation for women from rural and remote areas to access care and services. Cost effectivenessAn economic analysis carried out to inform the development of these Guidelines (see Appendix E) found that screening for congenital anomalies at 18–20 weeks is moderately cost-effective, without generating significant risks, although without driving substantive benefits. This excludes the positive psychological value of the information obtained from the ultrasound (which may be associated with improvements in fetal wellbeing) and benefits from the detection of placental problems and confirmation of gestational age, making these estimates fairly conservative. Discussing assessment of fetal development and anatomyNot all women will want an ultrasound and some may not understand the purpose of the assessment or think that it is being offered because there is something wrong with the pregnancy. In discussing the ultrasound scan, it is important to explain: that it is the woman’s decision whether the ultrasound takes place; where ultrasound services are available if the woman chooses to have one; that ultrasound does not detect all fetal and maternal anomalies; any costs involved for the woman and the timeframe for receiving results; and choices if any anomalies are detected (some parents may not want an ultrasound if there is no change in birth outcomes).
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