Early second-trimester sonography to improve the fetal anatomic survey in obese patients

Completion of Fetal Anatomy Evaluations in Women With Body Mass Index ≥ 50 kg/m2

OBJECTIVES

As maternal body mass index (BMI) increases, fetal anatomy ultrasound becomes more challenging, less sensitive, and less likely to be complete. We sought to report our experience of incomplete evaluation of anatomy in patients with BMI of 50 kg/m2 or greater.

METHODS

This is a retrospective cohort of singleton gestations in mothers with BMI of 50 kg/m2 or greater, undergoing anatomy evaluations between 2017 and 2021 at 9 maternal-fetal-medicine sites in Houston, TX. Patient variables and scan results were collected throughout pregnancy to provide a longitudinal assessment of the primary outcome, completion rate (percent of all scans which optimally captured 24 American Institute of Ultrasound in Medicine-recommended images). Secondary outcomes included the rate of optimal capture of each individual structure.

RESULTS

In total, 293 patients with BMI ≥50 kg/m2 were identified. Only 28% of initial scans were complete, but over the entire pregnancy, a complete anatomic evaluation was achieved in 76% of women, largely due to weekly ultrasounds done for antenatal testing later in pregnancy. Neither BMI, placental location, nor amniotic fluid volume affected completion rate. The most difficult views are the outflow tracts, 4-chamber view, and spine.

CONCLUSIONS

One quarter of women with BMI of 50 kg/m2 or greater will not have a complete fetal anatomic evaluation by the end of pregnancy, since even basic fetal anatomic views are technically challenging to complete. Solutions deserve further attention, and may include first trimester imaging, transvaginal imaging, and optimization of ultrasound machine settings.

First trimester anatomy ultrasound for patients with obesity: a randomized controlled trial

BACKGROUND

Second-trimester ultrasound is the standard technique for fetal anatomy evaluation in the United States despite international guidelines and literature that suggest that first-trimester timing may be superior in patients with obesity. First-trimester imaging performs well in cohorts of participants with obesity.

OBJECTIVE

Our aim was to compare the completion rate of a first-trimester fetal anatomy ultrasound scan with that of a second-trimester fetal anatomy ultrasound scan among pregnant people with a body mass index ≥35 kg/m2.

STUDY DESIGN

This randomized controlled trial enrolled participants with a body mass index ≥35 kg/m2 with a singleton gestation and who presented before 14+0/7 weeks of gestation. Participants were randomized to receive an ultrasound assessment of anatomy at either 12+0/7 to 13+6/7 weeks or at 18+0/7 to 22+6/7 weeks. The primary outcome was completion rate (percentage of scans that optimally imaged all the required fetal structures). Secondary outcomes included the necessity of a transvaginal approach, completion rates for each individual view, number of anomalies identified and missed in each group, scan duration, and patient perspectives. A 1-year pilot sample was analyzed using Bayesian methods for the primary outcome with a neutral prior and frequentist analyses for the remaining outcomes.

RESULTS

A total of 128 participants were enrolled, and 1 withdrew consent; 62 subjects underwent a first-trimester ultrasound scan and 62 underwent a second-trimester ultrasound scan. A total of 2 participants did not attend the research visits, and 1 sought termination of pregnancy. In the first-trimester group, 66% (41/62) of ultrasound scans were completed in comparison with 53% (33/62) in the second-trimester ultrasound group (Bayesian relative risk, 1.20; 95% credible interval, 0.91-1.73). When compared with a second-trimester scan plus a follow-up ultrasound, a first-trimester ultrasound plus a second-trimester ultrasound was equally successful in completing the anatomy views (76%). First-trimester anatomy ultrasound scans required a transvaginal approach in 63% (39/62) of cases and had a longer duration than a second-trimester ultrasound scan. No anomalies were missed in either group. First-trimester ultrasound participants who responded to a survey described that they were very satisfied with the technique.

CONCLUSION

In pregnant subjects with a body mass index ≥35 kg/m2, a single first-trimester anatomy ultrasound scan was more likely to obtain all the recommended anatomic views than a single second-trimester ultrasound scan. An evaluation of anatomy at 12+0/7 to 13+6/7 weeks' gestation plus an evaluation at 18+0/7 to 22+6/7 led to complete anatomic evaluation 4 weeks earlier than 2 second trimester scans. Assessment of ultrasound duration in a clinical setting is needed to ensure feasibility outside of a research setting.

A Matter of Time: Does Gestational Age Affect the Duration of the Fetal Anatomic Survey?

OBJECTIVE

To assess the average duration of detailed fetal anatomic surveys in pregnancy in relation to gestational age (GA) and the maternal body mass index (BMI) to determine optimal timing of the examination.

METHODS

This was a retrospective cohort study of gravidae presenting for detailed fetal anatomic examinations between January 1, 2010, and June 30, 2017. After excluding examinations expected to have longer duration (ie, multifetal, major fetal anomalies), there were a total of 6522 examinations performed between GAs of 18 weeks 0 days and 22 weeks 0 days. Women were grouped by BMI, and results were analyzed by logistic regression.

RESULTS

Gravidae of normal weight (BMI, 18.5-24.9 kg/m² ) had a decrease of 47.47 seconds of the examination time with each increasing week of gestation (P = .036). Overweight (BMI, 25-29.9 kg/m² ) gravidae similarly had a decrease of 66.31 seconds of the examination time with each additional week of gestation (P = .017). Underweight (BMI, 8.5 kg/m² ) and obese (BMI, ≥30 kg/m² ) gravidae did not have differences in the examination time with increasing GA. Increases in suboptimal examinations were noted with an increasing BMI (P < .001). There was a decreased frequency of suboptimal examinations in obese gravidae with a BMI of 40 kg/m² or higher with increasing GA (P = .037).

CONCLUSIONS

The duration of detailed fetal anatomic examinations decreased with increasing GA in normal-weight and overweight gravidae but not in obese gravidae. Performing the anatomy scan earlier in class I and II obese gravidae (BMI, 30-40 kg/m² ) may enable improved pregnancy management options without increasing the examination duration or likelihood of a suboptimal evaluation.

Delay of Fetal Anatomy Ultrasound Assessment Based on Maternal Body Mass Index Does Not Reduce the Rate of Inadequate Visualization

OBJECTIVES

To determine whether delay of initial anatomy ultrasound based on the maternal body mass index (BMI) reduces the rate of inadequate visualization compared to standard timing at 18^0/7 to 19^6/7 weeks.

METHODS

A retrospective study of singleton anatomy assessments was conducted at a tertiary care center in the 2-year period before (A, 2012-2014) and after (B, 2014-2016) protocol initiation. Assessments in period B were scheduled on the basis of the BMI in the first trimester: lower than 25 kg/m² , 18^0/7 to 19^6/7 weeks; 25 to 29.9 kg/m² , 19^0/7 to 20^6/7 weeks; 30 to 34.9 kg/m² , 20^0/7 to 21^6/7 weeks; 35 to 39.9 kg/m² , 21^0/7 to 22^6/7 weeks; and 40 kg/m² or higher, 22^0/7 to 23^6/7 weeks. In period A, assessments were scheduled between 18^0/7 and 19^6/7 weeks. The rate of inadequate visualization and repeated assessments in periods A and B were compared. Multivariable logistic regression, per-protocol, and BMI subgroup analyses were completed.

RESULTS

In total, 3491 pregnancies in period A and 3672 in period B were included. In period B, 74% were scheduled per protocol; however, this rate decreased for higher-BMI categories (52% for BMI ≥40 kg/m² ). The inadequate visualization rate was slightly higher in period B versus A (16.9% versus 15.0%; P = .03) and exceeded 35% for a BMI of 40 kg/m² or higher, with or without delay. After adjusting for maternal age and fetal presentation, period B had small increased odds of inadequate visualization versus period A (adjusted odds ratio, 1.2; 95% confidence interval, 1.02-1.38). Repeated assessment rates were similar in periods B and A (14.0% versus 13.1%; P = .25).

CONCLUSIONS

In pregnancies with obesity, a protocol delaying the initial assessment beyond 19^6/7 weeks based on the maternal BMI does not reduce the rate of inadequate visualization.

Should an Early Anatomy Ultrasound Scan Be Offered Routinely to Obese Pregnant Women?

OBJECTIVE

The primary objective of this study was to determine whether an early anatomic scan (EAS), either on its own or in combination with the routine transabdominal scan (R-TAS), would improve overall completion rates of the fetal anatomic survey in the obese pregnant woman. The study's secondary objectives were to compare patients' and sonographers' satisfaction with EAS versus R-TAS.

METHODS

A prospective observational study was carried out over a 2.5-year period including consecutive pregnant women with a pre-pregnancy BMI ≥30 kg/m² who consented at a dating ultrasound appointment to undergo EAS at 15 ± 1 GA in addition to the second trimester R-TAS. Anatomic structures were categorized as normal, not well seen, or abnormal by using the institutional 26-item anatomic standardized reporting template. Examination completion and study duration were recorded. Neonatal follow-up was performed to evaluate for any missed diagnoses. Patients' and sonographers' satisfaction questionnaires were completed.

RESULTS

A total of 120 pregnant women completed the study. Visualization of all anatomic components was complete in 14% at EAS and in 61% at R-TAS (combined completion rate, 90%). Mean scan time was 30.4 minutes at EAS and 51 minutes at R-TAS. No missed diagnoses of structural anomalies were identified at neonatal follow-up. EAS and R-TAS differed in terms of sonographers' reports of difficult or suboptimal scans (9% vs. 58%), well-seen anatomy (85% vs. 78%), and good visibility (44% vs. 12%). Most sonographers expressed a preference for performing EAS in future pregnancies, rather than the R-TAS (96% vs. 6%). Although patients reported greater satisfaction with EAS (93% vs. 74%), for reasons that could not be determined, they expressed a preference for R-TAS in a subsequent pregnancy (23% vs. 63%).

CONCLUSION

Performing EAS along with R-TAS improves completion rates for anatomic evaluation in the obese gravida and is associated with greater patient and sonographer satisfaction.

Does transvaginal ultrasound at 13-15 weeks improve anatomic survey completion rates in obese gravidas?

Objective: Obesity increases the difficulty of completing the fetal anatomic survey. This is of added concern in obese gravidas who are at higher risk of congenital fetal anomalies. We hypothesized that incorporation of an early transvaginal assessment could improve the completion rate of the fetal anatomic survey in obese women.Methods: We performed a prospective, longitudinal, blinded study of obese gravidas (BMI ≥ 35 kg/m²) comparing the use of a single early second trimester transvaginal ultrasound in addition to midtrimester transabdominal ultrasound versus traditional serial midtrimester ultrasound alone for completion of the anatomic survey. Transvaginal ultrasound for anatomy was performed between 13 0/7 and 15 6/7 week followed by midtrimester anatomic ultrasound, with each patient serving as her own control. Structures were marked as optimally or suboptimally viewed after each ultrasound. Sonographers and reviewers were blinded to images from the transvaginal ultrasound. Completion rates and gestational age at completion were compared between groups.Results: Fifty subjects were included. Fetal anatomic survey was completed in 62% using standard midtrimester assessment versus 78% with the addition of early transvaginal assessment (p = .04). The survey was completed at an earlier gestational age utilizing the transvaginal approach (22 0/7 ± 6 3/7) compared to traditional midtrimester transabdominal ultrasound approach (25 2/7 ± 5 3/7) p < .0005.Conclusions: Incorporation of an early transvaginal assessment of anatomy in obese women improved the rate of completion and led to earlier gestational age at completion of the fetal anatomic survey. Consideration should be given to including an early transvaginal sonogram as part of routine assessment of women with a BMI ≥ 35.

Pregnancy in Women with Obesity

Pregnancy in women with obesity is an important public health problem with short- and long-term implications for maternal and child health. Obesity complicates almost all aspects of pregnancy. Given the growing prevalence of obesity in women, obstetric providers need to understand the risks associated with obesity in pregnancy and the unique aspects of management for women with obesity. Empathic and patient-centered care, along with knowledge, can optimize outcomes for women and children.

Fetal Anatomic Imaging Between 11 and 14 Weeks Gestation

Fetal imaging between 11 and 14 weeks is a standard component of prenatal risk assessment for aneuploidy. Evaluating the fetus during this gestational age window provides the opportunity to reliably examine anatomic structures. Using a defined imaging protocol, approximately 50% of major abnormalities can be detected. Some abnormalities should almost always be detected, some may be detected on occasion and others are not currently detectable. Imagers must be familiar with embryologic patterns of development and natural history of anomalies. Patients must be informed of the limitations of early anatomic evaluation. Currently, early anatomic evaluation does not replace the standard second trimester evaluation.

The Role of Early Gestation Ultrasound in the Assessment of Fetal Anatomy in Maternal Obesity

OBJECTIVES

The 2012 Eunice Kennedy Shriver National Institute of Child Health fetal imaging consensus suggested that fetal anatomy ultrasound in obese pregnancies be performed at 20 to 22 weeks, with follow-up in 2 to 4 weeks if anatomy is incomplete. It was postulated that imaging in early gestation may improve visualization, although no prospective trials had been done to date.

METHODS

We performed a prospective longitudinal blinded trial comparing an early gestation ultrasound (13 + 0 to 15 + 6 weeks) with the traditional second-trimester ultrasound for completion of the fetal anatomy survey in obese patients. Inclusion criteria included singleton gestation, body mass index (BMI) more than 30, less than 16 + 0 weeks' gestation, and no karyotype abnormality; exclusion criteria included age younger than 18 years, more than 16 weeks' gestation at time of consent, and BMI less than 30. Participants received a transvaginal and/or transabdominal sonogram for fetal anatomic survey at 13 + 0 to 15 + 6 weeks' gestation (US1). Images from US1 were blinded to physicians and sonographers performing subsequent examinations. All participants underwent the traditional transabdominal sonogram at 18 to 24 weeks (US2). If US2 failed to complete the anatomic survey, a repeat transabdominal sonogram (2-US2) was performed 2 to 4 weeks later.

RESULTS

A total of 152 pregnancies met the criteria. Anatomy completion rate was 57.2% for US1 and 62.5% for US2, which was not statistically significant, even when stratified by BMI. Excluding the philtrum, the US1 performed better than US2 for class III obesity (65.5% versus 45.5% [P = .035]). Combination of US1 + US2 yielded a higher completion rate than US2 + 2-US2 (94.1% versus 83.6% [P = .0023]).

CONCLUSIONS

In the setting of maternal obesity, the addition of an ultrasound in early gestation may be of highest benefit for patients with class III obesity (BMI > 40 kg/m² ).

Optimal visualization of the fetal four-chamber and outflow tract views with transabdominal ultrasound in the morbidly obese: Are we there yet?

BACKGROUND

To compare optimal visualization of the four-chamber and outflow-tract views of the fetal heart on sonographic examination between morbidly obese (body mass index [BMI] ≥ 40 kg/m(2) ) and nonobese (BMI < 25 kg/m(2) ) pregnant women.

METHODS

In this retrospective cohort study, we included records and images from 509 pregnant women who had first undergone sonographic examination between 18 and 36 weeks' fetal gestational age.

RESULTS

Compared with the nonobese women, morbidly obese women had lower optimal visualization of the four-chamber and outflow-tract heart views: four-chamber view, morbidly obese, 83/186 (44.6%), versus nonobese, 283/323 (87.6%), and outflow-tract view, morbidly obese, 80/186 (43%) versus nonobese, 258/290 (89%); p < 0.0001 for each comparison. Similar outcomes were observed when the results from each subcategory of morbidly obese women (ie, BMI 40-49.9, 50-59.9, and ≥60 kg/m(2) ) were compared with that from nonobese women; p < 0.0001 for each comparison. These outcomes remained the same regardless of whether this comparison was made among those who had their examination before or at 19 weeks' or more gestational age. Among the morbidly obese women, there was no difference in optimal visualization of the four-chamber or outflow-tract views regardless of whether the examination was performed at <23 weeks' or at ≥23 weeks' gestational age: four-chamber view <23 weeks, 44.8% (78/174), versus four-chamber view ≥23 weeks, 41.7% (5/12); p = 0.8, and outflow-tract view <23 weeks, 43.1% (75/174), versus outflow-tract view ≥23 weeks, 41.7% (5/12); p = 0.9. After controlling for maternal age and race, the odds of visualizing the four-chamber and outflow-tract views in the morbidly obese were reduced compared with those in their nonobese counterparts: odds ratio (OR) for four-chamber, 0.13; 95% confidence interval (CI), 0.08-0.21, and OR for outflow-tract, 0.11; 95% CI, 0.07-0.17.

CONCLUSIONS

Optimal visualization of the fetal four-chamber and outflow-tract views was achieved in less than 50% of morbidly obese women, compared with almost 90% in nonobese women.