Third trimester ultrasound accuracy and delivery outcome in obese and morbid obese pregnant women

Is Obesity a Risk Factor for Disorders of Amniotic Fluid?

OBJECTIVES

Prior studies show conflicting evidence as to whether obesity in the absence of other medical or pregnancy-related conditions contributes to amniotic fluid disorders. The purpose of this study is to determine the association between late-pregnancy obesity with oligohydramnios (amniotic fluid index [AFI] ≤5 cm or maximum vertical pocket [MVP] <2 cm) and/or polyhydramnios (AFI ≥24 cm or MVP ≥8 cm).

METHODS

This is a retrospective cohort study of 961 women with singleton gestations who had one or more obstetrical ultrasounds at a single institution at 36 0/7 weeks gestation or beyond between August 1, 2015, and May 1, 2020. Patients were included if they had valid pregnancy dating and a documented AFI and/or MVP. Patients were categorized based on body mass index or BMI (eg, normal, overweight, Class I Obesity, Class II Obesity, or Class III Obesity).

RESULTS

A total of 6.2% of patients met criteria for oligohydramnios based on AFI, MVP or both (n = 60). There was no significant association between oligohydramnios and increasing BMI, regardless of obesity class (P = .21). In terms of polyhydramnios, 5.6% of patients met criteria based on AFI, MVP, or both (n = 54). Similarly, there was also no significant association between polyhydramnios and increasing BMI, regardless of obesity class (P = .66).

CONCLUSIONS

Elevated maternal BMI was not significantly associated with disorders of amniotic fluid, regardless of the severity of obesity.

Peripartum Prediction of Fetal Weight in Gravidas With Obesity

OBJECTIVES

Estimated fetal weight (EFW) is an important metric at delivery as neonates with abnormal birthweight and their mothers are at higher risk of birth complications. Data regarding optimal EFW assessment in gravidas with obesity is inconsistent, and with the increasing incidence of obesity, clarification of this question is crucial. We aimed to compare accuracy of ultrasound (US)-derived EFW and clinical assessments of EFW in predicting neonatal birthweight among gravidas with obesity.

METHODS

This prospective cohort study enrolled gravidas with obesity and a singleton pregnancy admitted for delivery at term. EFW was determined using either US biometry or clinical assessment (Leopold's maneuvers, Johnson's formula, and Insler's formula) at time of admission. Our primary outcome was accurate EFW, defined as EFW within 500 g of birthweight. Secondary outcomes included ability to predict small-for-gestational age (SGA) and large-for-gestational age (LGA) birthweights. These outcomes were compared between all EFW methods.

RESULTS

A total of 250 gravidas with a median body mass index of 36.4 kg/m2 were enrolled. Admission US outperformed Leopold's maneuvers in obtaining accurate EFW (81.6% versus 74.5%, P = .03). When comparing all methods, Johnson's and Insler's formulae performed the worst, accurately predicting EFW in only 27.4% and 14.3% of cases, respectively. Likewise, US-derived EFW outperformed Leopold's maneuvers and fundal height in the prediction of SGA and LGA neonates.

CONCLUSIONS

US is more accurate than clinical assessment of EFW in gravidas with obesity both for estimation of actual birthweight and prediction of abnormal birthweight. Universal late third-trimester or peripartum US for EFW should be considered in gravidas with obesity.

Accuracy of ultrasound in estimating fetal weight in New Zealand

Introduction

Ultrasound estimation of fetal weight is an important factor guiding antenatal management. We aimed to review the accuracy of ultrasound in predicting fetal weight and birthweight category and identify influencing factors.

Methods

We performed a retrospective study of term pregnant women who underwent ultrasound within 7 days of delivery at National Women's Health between January 2019 and January 2020. Stillbirths, major fetal anomalies and multiple pregnancies were excluded. Estimated fetal weight (EFW) was calculated using Hadlock formula and compared with birthweights. We evaluated change in weight categories due to these errors.

Results

Of 560 fetuses included, three quarters (n = 425, 76%) of EFWs were within 10% of birthweight. 135 fetuses had EFWs either less than 90% (n = 19) or greater than 110% (n = 116). Fetuses with EFW < 90% had longer times between scanning and delivery, lower EFW and higher maternal BMI. Fetuses with EFW > 110% were associated with higher EFW, later gestational age and older maternal age. US incorrectly estimated 71 (12.7%) fetal birthweight categories. Underestimated weight category (8.9%) was associated with higher maternal BMI.

Discussion

Inaccurate EFWs were more common at the extremes of fetal weight. A significant association was underestimation birthweight in mothers with increased BMI, who are at increased risk for perinatal and surgical complications.

Conclusion

Our accuracy of 76% correctly predicted EFWs compares favourably with previous studies. Clinicians and sonographers should be aware of the increased risk for inaccurate categorisation of fetuses at the extremes of EFW and in mothers with increased BMI.

The Relationship between Fetal Abdominal Wall Thickness and Intrapartum Complications amongst Mothers with Pregestational Type 2 Diabetes

OBJECTIVES

To evaluate the utility of fetal abdominal wall thickness (AWT) for predicting intrapartum complications amongst mothers with pregestational type 2 diabetes.

METHODS

This was a historical cohort study of pregnant mothers with pregestational type 2 diabetes delivering at a Canadian tertiary-care center between January 1, 2014, and December 31, 2018. Delivery records were reviewed to collect information about demographics and peripartum complications. Stored fetal ultrasound images from 36 weeks' gestation were reviewed to collect fetal biometry and postprocessing measurement of AWT performed in a standardized fashion by 2 blinded and independent observers. The relationship between fetal AWT was then correlated with risk of intrapartum complications including emergency Caesarean section (CS) and shoulder dystocia.

RESULTS

216 pregnant women with type 2 diabetes had planned vaginal deliveries and were eligible for inclusion. Mean maternal age was 31.3 years, and almost all were overweight or obese at the time of delivery (96.8%). Overall, the incidence of shoulder dystocia and emergency intrapartum CS was 7.4% and 17.6%, respectively. There was no difference in mean fetal AWT between those having a spontaneous vaginal delivery (8.2 mm (95% CI 7.9-8.5)) and those needing emergency intrapartum CS (8.1 mm (95% CI 7.4-8.8); p = 0.71) or shoulder dystocia (8.7 mm (95% CI 7.9-9.5); p = 0.23). There was strong interobserver correlation of AWT measurements (r = 0.838; p < 0.00001). The strongest association with intrapartum complications was birthweight (p = 0.003): with birthweight > 4000 grams, the relative risk of shoulder dystocia or CS is 2.75 (95% CI 1.74-4.36; p < 0.001).

CONCLUSIONS

There was no obvious benefit of AWT measurement at 36 weeks for predicting shoulder dystocia or intrapartum CS amongst women with type 2 diabetes in our population. The strongest predictor of intrapartum complications remained birthweight, and so studies for improving estimation of fetal weight and evaluating the role of intrapartum ultrasound for predicting risk of delivery complications are still needed.

A routine third trimester growth ultrasound in the obese pregnant woman does not reliably identify fetal growth abnormalities: A retrospective cohort study

BACKGROUND

In response to the challenges of assessing fetal growth in obese women, guidelines recommend routine third trimester ultrasound scans.

AIM

The aim of this study was to assess the diagnostic performance of this routine scan in obese women (body mass index (BMI) ≥ 35 kg/m² ).

METHODS

A retrospective cohort study of 1008 pregnancies with maternal BMI ≥ 35 kg/m² born after 37 weeks gestation at a Victorian hospital from 2015 to 2017. Multiple pregnancies and those affected by diabetes were excluded. Growth ultrasounds were performed between 34 + 0 and 36 + 6 weeks gestation. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the detection of large for gestational age (LGA > 90%) and small for gestational age (SGA < 10%) were calculated using ultrasound estimated fetal weight (EFW) or abdominal circumference (AC) and compared with gestational age and gender-based birthweight percentiles.

RESULTS

Using EFW, sensitivity for detecting SGA at birth was 8.1% (six of 74) with a PPV of 100%. Sensitivity for detecting LGA at birth was 61.0% (119 of 195), PPV 54.8%. Sensitivity, specificity, PPV and NPV percentages were all lower using AC. Only 40% of actual birthweight percentiles (405/1008) were within ±10 percentiles of their growth ultrasound EFW percentile.

CONCLUSION

The performance of a routine third trimester ultrasound in women with BMI ≥ 35 kg/m² suggests limited utility in helping identify aberrant fetal growth. This has important implications for the management of obese pregnant women.

Maternal and birth cohort studies in the Gulf Cooperation Council countries: a systematic review and meta-analysis

BACKGROUND

We systematically reviewed and chronicled exposures and outcomes measured in the maternal and birth cohort studies in the Gulf Cooperation Council (GCC) countries and quantitatively summarized the weighted effect estimates between maternal obesity and (1) cesarean section (CS) and (2) fetal macrosomia.

METHODS

We searched MEDLINE-PubMed, Embase, Cochrane Library, Scopus, and Web of Science electronic databases up to 30 June 2019. We considered all maternal and birth cohort studies conducted in the six GCC countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and United Arab Emirates (UAE)). We categorized cohort studies on the basis of the exposure(s) (anthropometric, environmental, medical, maternal/reproductive, perinatal, or socioeconomic) and outcome(s) (maternal or birth) being measured. Adjusted weighted effect estimates, in the form of relative risks, between maternal obesity and CS and fetal macrosomia were generated using a random-effects model.

RESULTS

Of 3502 citations, 81 published cohort studies were included. One cohort study was in Bahrain, eight in Kuwait, seven in Qatar, six in Oman, 52 in Saudi Arabia, and seven in the UAE. Majority of the exposures studied were maternal/reproductive (65.2%) or medical (39.5%). Birth and maternal outcomes were reported in 82.7% and in 74.1% of the cohort studies, respectively. In Saudi Arabia, babies born to obese women were at a higher risk of macrosomia (adjusted relative risk (aRR), 1.15; 95% confidence interval (CI), 1.10-1.20; I2 = 50%) or cesarean section (aRR, 1.21; 95% CI, 1.15-1.26; I2 = 62.0%). Several cohort studies were only descriptive without reporting the magnitude of the effect estimate between the assessed exposures and outcomes.

CONCLUSIONS

Cohort studies in the GCC have predominantly focused on reproductive and medical exposures. Obese pregnant women are at an increased risk of undergoing CS delivery or macrosomic births. Longer-term studies that explore a wider range of environmental and biological exposures and outcomes relevant to the GCC region are needed.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42017068910.

Estimation of fetal weight near term: comparison between ultrasound and symphysis-fundus evaluation by Johnson's rule

INTRODUCTION

The fetal weight estimation is commonly performed by ultrasound but the manual method is also applied in developing countries due to the lack of scan availability and in western countries for the management of low-risk pregnancy managed autonomously by the midwives. The most applied method to estimate fetal weight measures the longitudinal diameter of the symphysis-fundus according to Johnson's rule. The aim of the present study is to evaluate the reliability of the symphysis-fundus method with respect to the ultrasound to estimate fetal weight in low risk pregnancies according to the classification of adequate, small and large for gestational age.

MATERIALS AND METHODS

Two hundred twenty low-risk women referred to the clinic for the management of term pregnancy were enrolled for the study. The following data were collected: age, body mass index, parity, values of symphysis-fundus evaluation according to Johnson's rule, ultrasound fetal weight estimation values, and birthweight.

RESULTS

Considering the whole sample, fetal weight was estimated similarly by the manual method and with the ultrasound (79.5 versus 85% of the cases; n.s.). However, in overweight women, the ultrasound better estimates fetal weight in respect to manual method (94.4 versus 80.3% of the cases; p < .02) and similarly in obese women also ultrasound performed better in comparison to manual method (91.8 versus 71.4% of the cases; p < .01).

CONCLUSIONS

The manual evaluation could be considered a reliable method to assess fetal weight for the management of low-risk pregnancies near term to optimize the resources and also offer a safe nonmedical approach. Further studies should clarify the accuracy of the manual method to estimate fetal weight in overweight and obese women, also considering the great increase of the obesity incidence in the obstetric population.