For practicing obstetricians, the increasing prevalence of obesity in women of reproductive age has led to debate regarding how care should be modified to optimize outcome. Obesity, parity (and therefore age) and diabetes all sort together and together increase the risk for fetal anomalies in obese women compared with their normal-weight counterparts. One clinical problem in this population is inadequacy of sonographic assessment of fetal anatomy.
In this article by Fuchs et al., the authors assess the feasibility of performing complete ultrasound screening on the obese gravida, with a primary question being whether there are easily modifiable factors that would allow improved completion rates in these women. They evaluated the influence of a variety of factors, including fetal position, gestational age, abdominal thickness, sonographer experience, equipment and scan duration, on the feasibility of completing both biometric and anatomical imaging during a single ultrasound examination between 20 and 24 weeks. Each image was reviewed in a blinded fashion for quality, and scores compared between obese and non-obese patients.
The study was prospective, appropriately controlled and performed at a single high-quality laboratory, with a single image reviewer. The completion rate was high for both obese and non-obese groups (> 70%), with improvement associated with lower maternal abdominal thickness, increased time, newer equipment, fetal back-down position and greater sonographer experience, confirming what has long been expert opinion. Image quality was notably poorer in more obese women, although body mass index did not necessarily reflect the quality or ease of scanning, as morbidly obese patients with an inferiorly displaced panniculus actually had less adiposity over the uterus.
However, this study had limitations. It should be noted that obesity is not a variable to which the sonographer can be blinded, and therefore the care, time, effort and attention afforded the obese patients may have varied, depending on the particular patient's morphology and sonographer persistence. Additionally, although the reviewer of the images was blinded, there is only so much blinding to depth, scale and quality that is possible. No data are presented on genetic history, parity and screening risks, which, if known to the sonographer, may have increased the time and care of ultrasound screening. The number of obese patients included was small, and conclusions in this group limited, especially for Class II (n = 50) and Class III obesity (n = 20), although the authors' data mirror completion rates in previous studies with larger numbers of morbidly obese women.
Finally, the reader must remember that, although completion was improved with slightly later gestational ages (> 24 weeks), delaying evaluation limits treatment and termination options for many women with fetal anomalies. Additionally, it is important to note that this study does not attempt to evaluate the ability of ultrasound to detect anomalies, a question that would require a much larger study with an end-point of neonatal outcome in addition to completion of ultrasound. Non-detection is a known problem in the obese gravida, and it remains to be seen whether any of the studied factors may improve detection rates for anomalies in obese patients.