The July issue of Ultrasound in Obstetrics & Gynecology has a special focus on fetal weight, with relevant articles on the accuracy of estimated fetal weight formulae, a new birth-weight reference chart that includes fetuses still in utero, and the screening and management of small-for-gestational-age fetuses. Also included in this issue is an ISUOG Guideline on intrapartum ultrasound providing guidance to practitioners on when ultrasound in labor is clinically indicated and how sonographic findings may affect labor management.
Please see below a selection of articles from the July issue of the Journal chosen specially by the UOG team. To view all UOG content, become an ISUOG member today or login and upgrade.
Assessment of weight
Small-for-gestational age (SGA) is associated with increased risk of adverse perinatal outcome and its identification through fetal size assessment has become an established part of antenatal care. An Opinion article by Basky Thilaganathan discusses ultrasound fetal weight assessment in the context of articles included in this issue of UOG, with regards to contentious issues such as which fetal biometry reference chart should be used, and whether fetal arterial redistribution may be more strongly associated with perinatal death at term.
Although many formulae incorporating different combinations of fetal biometric parameters have been presented for estimated fetal weight, there is no universally accepted formula. In an Original Article by Hammami et al., a new formula was developed and evaluated alongside all previous ones. It was found that, despite efforts to develop new models, the one reported in 1985 by Hadlock et al., incorporating head circumference, abdominal circumference and femur length, is the most accurate and can be used for assessment of all babies, including those suspected to be either small or large.
In reported reference ranges, the median birth weight according to gestational age for babies born preterm is substantially lower than the median estimated fetal weight. In an Original Article, Nicolaides et al. suggest that birth-weight reference charts over represent pathological pregnancies, leading to underestimation of growth restriction in preterm birth. The authors establish a birth-weight chart for all babies at a given gestational age, including those still in utero, finding it to overcome underestimation of growth restriction in preterm birth, and argue that, although birth weight depends on maternal characteristics such as racial origin, adjustment for such characteristics may be inappropriate (download the accompanying Journal Club slides).
Screening and management of SGA
In pre-eclampsia (PE), many fetuses are SGA, and preterm SGA, in the absence of PE, is associated with similar maternal factors and biomarker profile as in preterm PE. In an Original Article by Tan et al., the data from the SPREE and ASPRE trials were used to examine the effect of first-trimester screening for PE on the prediction of SGA neonates, as well as the effect of prophylactic use of aspirin on the prevention of SGA. It was found that first-trimester screening for PE by a combination of maternal characteristics and biomarkers identifies a high proportion of cases of preterm SGA that can be prevented by the prophylactic use of aspirin. View the accompanying video summary here:
Many SGA fetuses are merely constitutionally small and therefore probably not at increased risk of adverse outcome. There is therefore uncertainty regarding the optimal management and timing of delivery of affected pregnancies. In an Original Article by Veglia et al., expectant management after 37 weeks’ gestation for low-risk babies was compared with delivery recommended at 37 weeks. It was found that protocol-based management of SGA babies may improve outcome, and that identification of moderate SGA should not in isolation prompt delivery. This article is accompanied by a Referee Commentary by Kim Boers, in which the findings of the article are discussed further.
Fetal Doppler assessment as an alternative in late pregnancy
Recent work has challenged the idea of fetal size as defining pregnancies at high risk of adverse outcome. Markers for placental dysfunction could arguably play a larger role in the identification of high-risk term pregnancies. Two Original Articles in this issue of the Journal provide support for this. Binder et al. evaluated the difference in mean uterine artery (UtA) pulsatility index (PI) between the second and third trimesters, analyzing the association of de-novo increases with adverse perinatal outcome. It was found that the development of hypertensive disorders of pregnancy and SGA birth in the third trimester are related principally to high mid-gestation UtA-PI as well as de-novo increase in third-trimester UtA-PI. This article is accompanied by a Referee Commentary by José Morales-Roselló, in which the findings of the article are discussed further. Monaghan et al. examined the associations of UtA Doppler indices and the cerebroplacental ratio with perinatal outcome at term, demonstrating that high UtA resistance at term is associated independently with an increased risk of severe adverse perinatal outcome, regardless of fetal size.
Also included in this issue…
New ISUOG Practice Guidelines on intrapartum ultrasound
The assessment and management of women in labor is traditionally based on clinical findings. Whilst there is growing evidence to suggest that ultrasound-guided management may be more effective, its use is not yet widespread and there is currently no consensus regarding its application in clinical practice. A new ISUOG Practice Guideline on intrapartum ultrasound presents a review of the published techniques of ultrasound in labor and provides guidance to practitioners on when ultrasound in labor is clinically indicated and how the sonographic findings may affect labor management.
Coming up in the next issue of UOG are two research papers and an accompanying Opinion on fetal aortic valvuloplasty.