Obstetrical sonography in obese women: a review

Challenges of prenatal diagnosis in obese pregnant women

Obesity rates are increasing world-wide with most of the increase in women of the reproductive age group. While recognised as an important contributor to non-communicable diseases, pregnant women with obesity are particularly at risk of not only maternal and pregnant complications but also have an increased risk of congenital malformations. Furthermore, pregnant obese women are more likely to be older and therefore at a greater risk of aneuploidy. Prenatal diagnosis in these women especially those who are morbidly obese is challenging due not only to their weight but the implications of the increase adiposity on biochemical markers of aneuploidy. In this review we discuss the current challenges in providing prenatal diagnosis for these women including those related to the ergonomics of ultrasound and those inherent in them because of their obesity. Appropriate counselling for these women should include the lower sensitivity of the tests, the difficulties in performing some of the procedures (imaging and invasive testing) as well as the increased risk of structural abnormalities related to their obesity.

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.

Obesity in Pregnancy: ACOG Practice Bulletin, Number 230

Obstetrician-gynecologists are the leading experts in the health care of women, and obesity is the most common medical condition in women of reproductive age. Obesity in women is such a common condition that the implications relative to pregnancy often are unrecognized, overlooked, or ignored because of the lack of specific evidence-based treatment options. The management of obesity requires long-term approaches ranging from population-based public health and economic initiatives to individual nutritional, behavioral, or surgical interventions. Therefore, an understanding of the management of obesity during pregnancy is essential, and management should begin before pregnancy and continue through the postpartum period. Although the care of the obese woman during pregnancy requires the involvement of the obstetrician or other obstetric care professional, additional health care professionals, such as nutritionists, can offer specific expertise related to management depending on the comfort level of the obstetric care professional. The purpose of this Practice Bulletin is to offer an integrated approach to the management of obesity in women of reproductive age who are planning a pregnancy.

Optimal timing of the second trimester fetal ultrasound in the obese gravida

OBJECTIVES

Obesity is increasingly prevalent in the obstetric patient population, becoming one of the most commonly occurring risk factors in obstetric practice. Obesity has implications for maternal and fetal morbidity; in fact, some data suggest it is associated with higher rates of fetal anomaly. Coincident with this, maternal obesity poses an inherent challenge for ultrasound quality. The objective of this study is to investigate the relationship between ultrasound completion rates and advancing gestational age in obese gravidas, and to help identify an ideal gestational age to perform the second trimester ultrasound for fetal evaluation in the obese patient population. We hypothesized that in the obese patient, the odds of a completed scan would increase with each gestational age week, as fetal size increases.

METHODS

This is a retrospective cohort study at a single tertiary care center. Inclusion criteria were pregnant women with BMI greater than 30 who had second trimester fetal ultrasound and delivery at our institution. Exclusion criteria were pregnancies without documented BMI, ultrasound not performed between 18 0/6 and 21 6/7 weeks, multiple gestations, or ultrasound performed for indication other than fetal anatomic assessment. Ultrasound reports were considered incomplete if they indicated suboptimal or non-visualization of any anatomic structures included in the comprehensive anatomic survey. Demographic data was compared using Student's t test and chi-square analysis where appropriate. Chi-square analysis was used to compare rates of completed surveys. p < .05 was considered significant.

RESULTS

After application of eligibility criteria, our cohort included 1,954 subjects. When comparing subjects with a completed scan to those with an incomplete scan, there were more white subjects in the incomplete group (p = .012), but other analyzed demographics were similar between groups. When using 18 weeks as a referent group, with each additional completed week of gestation, subjects were more likely to have a completed scan, at 19 weeks (OR 1.29, CI 1.05-1.58); at 20 weeks (OR 1.46, CI 1.1-1.95); at 21 weeks (OR 2.12, CI 1.42-3.17) (p < .05 for each). This association persisted when adjusting for demographic factors. To identify the optimal timing for the second trimester ultrasound for fetal evaluation, we re-analyzed the data using each completed week of gestational age as the referent group. When using 19 weeks as the referent group, the odds of a complete scan were lower at 18 weeks, and higher at 21 weeks, but not different at 20 weeks. When using 20 weeks as the referent group, the odds of a complete scan were lower at 18 weeks, but not different at 19 or 21 weeks. Finally, when using 21 weeks as the referent group, the odds of a complete scan were lower at 18 and 19 weeks, but not different at 20 weeks.

CONCLUSIONS

In this cohort of obese gravidas, the odds of having a completed anatomic survey continued to improve until 21 weeks gestational age. When comparing completed scans between each week, 18 weeks demonstrated consistently lower odds of a complete scan, however 20 weeks did not differ significantly from 19 weeks. Therefore, consideration should be made to perform the initial second trimester ultrasound for fetal evaluation in obese patients at 19 weeks gestational age to optimize completion rates while minimizing scans performed at advancing gestational ages.

Second trimester ultrasound detection of fetal anomalies in the obese obstetrical population: a systematic review protocol

REVIEW QUESTION/OBJECTIVE

The objective of this review is to identify, appraise and synthesize the best available evidence on the impact of maternal obesity on mid second trimester ultrasound detection of fetal anomalies in pregnancy.

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 ).

Clinical management of pregnancy in the obese mother: before conception, during pregnancy, and post partum

The global epidemic of obesity has led to an increasing number of obese women of reproductive age. Obesity is associated with reduced fertility, and pregnancies complicated by maternal obesity are associated with adverse outcomes, including increased risk of gestational diabetes, pre-eclampsia, preterm birth, instrumental and caesarean births, infections, and post-partum haemorrhage. The medical and obstetric management of obese women is focused on identifying, addressing, and preventing some of these associated complications, and is a daunting challenge given the high percentage of patients with obesity and few therapeutic options proven to improve outcomes in this population. The UK's National Institute for Health and Care Excellence guidelines and the American College of Obstetricians and Gynecologists recommend that all pregnant women follow a healthy diet, and consider at least half an hour of moderate physical activity per day during pregnancy. However, although obese women are often directed to seek the advice of a nutritionist and to limit gestational weight gain, guidelines for the management of pregnancy and delivery in this high-risk group are lacking. The post-partum period represents an important opportunity to optimise maternal health before the next pregnancy. As many of the physiological changes of pregnancy associated with maternal obesity are present from early pregnancy onward, reducing maternal obesity before conception is probably the best strategy to decrease the health burden associated with maternal obesity.

What Is the Rate of Incomplete Fetal Anatomic Surveys During a Second-Trimester Scan? Retrospective Observational Study of 4000 Nonobese Pregnant Women

OBJECTIVES

The purpose of this study was to estimate the rate of incomplete fetal anatomic surveys during a second-trimester scan due to an unfavorable fetal position in a nonobese population.

METHODS

All pregnant women who came to the Altamedica Fetal-Maternal Medical Center, a specialized center for prenatal diagnosis, for a routine second-trimester scan between January 2012 and April 2013 were retrospectively included in the analysis. Patients with a body mass index higher than 30.0 kg/m(2) or anterior fibroids larger than 5 cm were not included in the study.

RESULTS

Of 4000 pregnant women admitted for a second-trimester scan, 169 (4.2%) came back within 2 weeks to complete the examination because of an unfavorable fetal position. In particular, 104 (2.6%) needed visualization of only 1 view, and 65 (1.6%) needed more than 1 view. The most difficult organ to visualize was the corpus callosum, in 73 cases (1.8%); the face was not visualized in 69 cases (1.7%); the cerebellar vermis was not seen in 47 fetuses (1.1%); and the heart could not be completely examined in 40 fetuses (1.0%). Of the 4000 women, 169 (4.2%) had a nonexhaustive scan; 149 (3.7%) needed a second scan to complete the second-trimester survey; 14 (0.35%) needed a third scan; and 2 (0.05%) remained with a not completely exhaustive scan.

CONCLUSIONS

There is always a small percentage of incomplete fetal anatomic surveys during a second-trimester scan, which cannot be modified by the sonographer's skill or by technical sonographic innovations.

Elevated hsa-miR-99a levels in maternal plasma may indicate congenital heart defects

The current standard for prenatal screening is mostly based on biochemical marker tests and the use of ultrasonography. There is no secure stand-alone screening marker for congenital heart defects (CHDs). MicroRNAs (miRNAs) that are associated with cardiogenesis enter the maternal peripheral bloodstream during pregnancy and allow non-invasive prenatal testing (NIPT). The present study investigated the plasma expression profile of fetal hsa-miR-99a in maternal blood. Peripheral blood samples were collected from 39 pregnant patients, comprising 22 with CHD-positive fetuses and 17 with CHD-free controls. miRNAs were isolated from the maternal serum and reverse transcription-quantitative polymerase chain reaction was carried out to determine the expression of hsa-miR-99a. While the miRNA concentrations were almost identical among the affected and control groups (5.54 vs. 6.40 ng/µl), significantly upregulated hsa-miR-99a levels were identified in the affected group (1.78×10^-2±3.53×10^-2 vs. 1.09×10^-3±3.55×10^-3 ng/µl, P=0.038). In conclusion, according to the present study, hsa-miR-99a is involved in cardiac malformation and may serve as a biomarker during fetal development, and therefore presents as a candidate for monitoring cardiomyogenesis and potential use as a NIPT-biomarker for fetal CHD.

An Absent Right Umbilical Artery Versus Absent Lt and the Prognostic Implications for the Fetus

A single umbilical artery (SUA) is one of the most common malformations in a fetus, with approximately a 1% occurrence rate. A retrospective study of 108 fetuses with a SUA was done to determine if the laterality of the SUA made a difference in fetal prognosis. An absent right umbilical artery was found in 42 (38.9%) of cases and an absent left umbilical artery in 66 (61.1%) cases. When correlated with fetal outcome, there was a closer association between an absent right umbilical artery with genitourinary anomalies, cardiac defects, and chromosomal abnormalities. There was a nine times greater likelihood (95% confidence interval of a 3 to 27 times greater probability) of a fetal anomaly with an absent right umbilical artery than with an absent left umbilical artery.

'Ultrasound is an invaluable third eye, but it can't see everything': a qualitative study with obstetricians in Australia

Background

Obstetric ultrasound has come to play a significant role in obstetrics since its introduction in clinical care. Today, most pregnant women in the developed world are exposed to obstetric ultrasound examinations, and there is no doubt that the advantages of obstetric ultrasound technique have led to improvements in pregnancy outcomes. However, at the same time, the increasing use has also raised many ethical challenges. This study aimed to explore obstetricians’ experiences of the significance of obstetric ultrasound for clinical management of complicated pregnancy and their perceptions of expectant parents’ experiences.

Methods

A qualitative study was undertaken in November 2012 as part of the CROss-Country Ultrasound Study (CROCUS). Semi-structured individual interviews were held with 14 obstetricians working at two large hospitals in Victoria, Australia. Transcribed data underwent qualitative content analysis.

Results

An overall theme emerged during the analyses, ‘Obstetric ultrasound - a third eye’, reflecting the significance and meaning of ultrasound in pregnancy, and the importance of the additional information that ultrasound offers clinicians managing the surveillance of a pregnant woman and her fetus. This theme was built on four categories: I:‘Everyday-tool’ for pregnancy surveillance, II: Significance for managing complicated pregnancy, III: Differing perspectives on obstetric ultrasound, and IV: Counselling as a balancing act. In summary, the obstetricians viewed obstetric ultrasound as an invaluable tool in their everyday practice. More importantly however, the findings emphasise some of the clinical dilemmas that occur due to its use: the obstetricians’ and expectant parents’ differing perspectives and expectations of obstetric ultrasound examinations, the challenges of uncertain ultrasound findings, and how this information was conveyed and balanced by obstetricians in counselling expectant parents.

Conclusions

This study highlights a range of previously rarely acknowledged clinical dilemmas that obstetricians face in relation to the use of obstetric ultrasound. Despite being a tool of considerable significance in the surveillance of pregnancy, there are limitations and uncertainties that arise with its use that make counselling expectant parents challenging. Research is needed which further investigates the effects and experiences of the continuing worldwide rapid technical advances in surveillance of pregnancies.

Limitations of Aneuploidy and Anomaly Detection in the Obese Patient

Obesity is a worldwide epidemic and can have a profound effect on pregnancy risks. Obese patients tend to be older and are at increased risk for structural fetal anomalies and aneuploidy, making screening options critically important for these women. Failure rates for first-trimester nuchal translucency (NT) screening increase with obesity, while the ability to detect soft-markers declines, limiting ultrasound-based screening options. Obesity also decreases the chances of completing the anatomy survey and increases the residual risk of undetected anomalies. Additionally, non-invasive prenatal testing (NIPT) is less likely to provide an informative result in obese patients. Understanding the limitations and diagnostic accuracy of aneuploidy and anomaly screening in obese patients can help guide clinicians in counseling patients on the screening options.

Super obesity in pregnancy: difficulties in clinical management

As the obesity pandemic continues in the United States, obesity in pregnancy has become an area of interest. Many studies focus on women with body mass index (BMI) ⩾ 30 kg m(-2). Unfortunately, the prevalence of patients with BMI ⩾ 50 kg m(-2) is rapidly increasing, and there are few studies specifically looking at pregnant women in this extreme category. The purpose of this article is to highlight some of the challenges faced and review the literature available to help guide obstetricians who might encounter such patients.

[Could we perform quality second trimester ultrasound among obese pregnant women?]

OBJECTIVE

To compare the quality of second trimester ultrasound images and their anatomical quality scores among obese women and those with a normal body mass index (BMI).

MATERIALS AND METHODS

This prospective study, which took place from 2009 to 2011, included every obese pregnant woman (prepregnancy BMI greater than 30 kg/m(2)) who had an ultrasound examination at 20 to 24 weeks in our hospital and a control group with a normal BMI (20-24.9kg/m(2)) who had the same examination. A single operator evaluated the quality of all images, reviewing the standardized ultrasound planes - three biometric and six anatomical - required by French guidelines and scoring the quality of the six anatomical images. Each image was assessed according to 4-6 criteria, each worth one point. We sought excellent quality, defined as the frequency of maximum points for a given image.

RESULTS

The obese group included 223 women and the control group 60. The completion rate for each image was at least 95 % in the control group and 90 % in the obese group, except for diaphragm and right outflow tract images. Overall, the excellence rate varied from 35 % to 92 % in the normal BMI group and 18 % to 58 % in the obese group and was significantly lower in the latter for all images except abdominal circumference (P=0.26) and the spine (P=0.06). Anatomical quality scores were also significantly lower in the obese group (22.3 vs. 27.2 ; P=0.001).

CONCLUSION

Image quality and global anatomical scores in second trimester ultrasound scans were significantly lower among obese than normal-weight women.

Factors affecting feasibility and quality of second-trimester ultrasound scans in obese pregnant women

OBJECTIVES

To evaluate the feasibility of completing in one session a second-trimester ultrasound scan in obese pregnant women, to compare the quality of images obtained with those of non-obese women and to analyze factors that can improve the completion rate.

METHODS

This prospective study, from 2009 to 2011, included all obese pregnant women (prepregnancy body mass index (BMI) > 30 kg/m2) who had an ultrasound examination at 20-24 weeks in our department, and a control group of pregnant women with normal BMI (20-24.9 kg/m2) who had the same examination. A single operator reviewed the standardized ultrasound images (three biometric and six to assess key anatomical features) required under French guidelines, to assess their presence, evaluate the quality of all images and score the quality of the six anatomical images. Each image was assessed according to between four and six criteria, each worth one point. We sought excellent quality, defined as the frequency of maximum points for a given image type. The factors associated with completing the scan in one session were evaluated with multivariate logistic regression.

RESULTS

The obese group included 223 women and the control group 60; a complete scan in one session was achieved in 70.4% and 81.7% of these, respectively (P = 0.08). The completion rate for each image type was at least 95% in the control group and 90% in the obese group, except for diaphragm and right outflow tract images. Significant factors associated with completing the scan in the multivariate model were: having 10 additional minutes for the scan (P = 0.03), moving the fetus so that the back was in posterior or lateral position (P = 0.01), more experienced sonographer (P = 0.03) and thinner maternal abdominal wall thickness (P = 0.01). Overall, the excellence rate varied from 35% to 92% in the normal BMI group and from 18% to 58% in the obese group, and was significantly lower in the latter for all images except abdominal circumference (P = 0.26) and spine (P = 0.06). Anatomical quality scores were also significantly lower in the obese group (22.3 vs. 27.2; P = 0.001).

CONCLUSION

Although ultrasound scans of obese pregnant women are feasible, image quality and global anatomical scores are significantly lower among obese than normal-weight women. However, certain simple improvements may increase fetal visualization.