Systematic error and cognitive bias in obstetric ultrasound

Looking back to look forward: Has the time arrived for active management of obstetricians in placenta accreta spectrum?

Placenta accreta spectrum (PAS) is a relatively new obstetric condition which, until recently, was poorly understood. The true incidence is unknown because of the poor quality and heterogeneous diagnostic criteria. Classification systems have attempted to provide clarity on how to grade and diagnose PAS, but these are no longer reflective of our current understanding of PAS. This is particularly true for placenta percreta, which referred to extrauterine disease, as recent studies have demonstrated that placental villi associated with PAS have minimal potential to invade beyond the uterine serosa. It is accepted that PAS is a direct consequence of previous iatrogenic uterine injury, most commonly a previous cesarean section. Here, we "look back to look forwards"-starting with the primary predisposing factor for PAS, an iatrogenic uterine injury and subsequent wound healing. We then consider the evolution of definitions and diagnostic criteria of PAS from its first description over a century ago to current classifications. Finally, we discuss why modifications to the current classifications are needed to allow accurate diagnosis of this rare but life-threatening complication, while avoiding overdiagnosis and potential patient harm.

Use of artificial intelligence in obstetric and gynaecological diagnostics: a protocol for a systematic review and meta-analysis

INTRODUCTION

Emerging developments in applications of artificial intelligence (AI) in healthcare offer the opportunity to improve diagnostic capabilities in obstetrics and gynaecology (O&G), ensuring early detection of pathology, optimal management and improving survival. Consensus on a robust AI healthcare framework is crucial for standardising protocols that promote data privacy and transparency, minimise bias, and ensure patient safety. Here, we describe the study protocol for a systematic review and meta-analysis to evaluate current applications of AI in O&G diagnostics with consideration of reporting standards used and their ethical implications. This protocol is written following the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) 2015 checklist.

METHODS AND ANALYSIS

The study objective is to explore the current application of AI in O&G diagnostics and assess the reporting standards used in these studies. Electronic bibliographic databases MEDLINE, EMBASE and Cochrane will be searched. Study selection, data extraction and subsequent narrative synthesis and meta-analyses will be carried out following the PRISMA-P guidelines. Included papers will be English-language full-text articles from May 2015 to March 2024, which provide original data, as AI has been redefined in recent literature. Papers must use AI as the predictive method, focusing on improving O&G diagnostic outcomes.We will evaluate the reporting standards including the risk of bias, lack of transparency and consider the ethical implications and potential harm to patients. Outcome measures will involve assessing the included studies against gold-standard criteria for robustness of model development (Transparent Reporting of a multivariable prediction model for Individual Prognosis Or Diagnosis, model predictive performance, model risk of bias and applicability (Prediction model Risk Of Bias Assessment Tool and study reporting (Consolidated Standards of Reporting Trials-AI) guidance.

ETHICS AND DISSEMINATION

Ethical approval is not required for this systematic review. Findings will be shared through peer-reviewed publications. There will be no patient or public involvement in this study.

PROSPERO REGISTRATION NUMBER

CRD42022357024 .

The Accuracy of Sonographically Estimated Fetal Weight and Prediction of Small for Gestational Age in Twin Pregnancy-Comparison of the First and Second Twins

Accurate sonographic estimation of fetal weight is essential for every pregnancy, especially in twin gestation. We conducted a retrospective analysis of the sonographically estimated fetal weight (sEFW) of all twin gestations performed within 14 days of delivery in a single center that aimed to evaluate the accuracy of sEFW in predicting neonatal weight and small for gestational age (SGA) by comparing the first fetus to the second. A total of 190 twin gestations were evaluated for the study. There was no statistically significant difference in the sEFW between the first and the second twins, but the second twin had a statistically significant lower birth weight (2434 vs. 2351 g, p = 0.028). No difference was found in median absolute systematic error (p = 0.450), random error, or sEFW evaluations that were within 10% of the birth weight between the fetuses (65.3% vs. 67.9%, p = 0.587). Reliability analysis demonstrated an excellent correlation between the sEFW and the birth weight for both twins; however, the Euclidean distance was slightly higher for the first twin (12.21%). For SGA prediction, overall, there was a low sensitivity and a high specificity for all fetuses, with almost no difference between the first and second twins. We found that sEFW overestimated the birth weight for the second twin, with almost no other difference in accuracy measures or SGA prediction.

Expected-value bias in mid-trimester preterm birth screening

OBJECTIVES

Cervical length (CL) measurement ≤ 25 mm on mid-trimester ultrasound scan is a known risk factor for preterm birth, for which vaginal progesterone is recommended. The aims of this study were to evaluate whether CL measurement is affected by observer bias and to assess the impact on short cervix prevalence of masking CL measurement during routine mid-trimester ultrasound scan.

METHODS

This was a flash study designed for a 2-month period (October and November 2018) at Cruces University Hospital (Bizkaia, Spain), in which all CL measurements from routine mid-trimester scans were masked. During the study period, there was no modification of the routine screening method, and women with a short cervix were prescribed 200 mg vaginal progesterone daily as per usual. The control group included women examined in a 2-month period (April and May 2018) prior to the study, in which CL measurements were taken as usual by a non-blinded operator. The primary outcome was the prevalence of short cervix in each group.

RESULTS

A total of 983 CL measurements were analyzed, including 457 in the blinded group and 526 in the control group. The prevalence of short cervix was 2.7% in the non-blinded group and 5.5% in the blinded group (P = 0.024). We identified a statistically significant difference in the incidence of CL of 24-25 mm between the two groups, with a lower prevalence in the non-blinded vs blinded group (0.6% vs 2.4%; P < 0.005). Moreover, the distribution of CL values was normal in the blinded group, in contrast to the non-blinded group, which was characterized by skewed distribution of CL values.

CONCLUSIONS

Expected-value bias exists and should be taken into account when measuring CL in mid-trimester preterm birth screening. Blinding has demonstrated to be an effective strategy to improve the performance of CL screening in clinical practice. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

3-D modeling applications in ultrasound education: a systematic review

Ultrasound offers a real-time 2-D view of structures within the human body. While many medical education programs have already dedicated a portion of their curriculum to ultrasound, others are concerned about cost, accessibility and limits to student practice. Student benefit may be affected by cognitive errors, which are in part owing to the mental heuristics required to visualize a 3-D structure by interpreting a 2-D image. A possible solution to eliminating subjectivity in ultrasound interpretation is the use of 3-D models to augment the traditional 2-D ultrasound experience. PubMed, Embase and Web of Science were searched for primary literature exploring relationships between 3-D modeling applications and their use in ultrasound education. The search and review process was guided by the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) checklist. Overall, 14 of the included 16 studies indicated a significant improvement in medical education of ultrasound with the intervention of 3-D modeling applications. This systematic review confirms that 3-D modeling applications benefit student learning in ultrasound education while illuminating the need for more research in this field.

Late presentation of a heterotopic pregnancy at 19 weeks of gestation leading to maternal collapse: A case report

Background

Heterotopic pregnancy is a rare form of pregnancy that involves implantation of simultaneous pregnancies at two sites. They are normally identified in early gestation when patients become symptomatic with vaginal bleeding or abdominal pain.

Case Presentation

A 35-year-old woman (para 0, gravida 2) presented to the emergency department in haemorrhagic shock at 19 weeks and 5 days of gestation. On assessment she was hemodynamically unstable and was found to have a large hemoperitoneum on ultrasound. She subsequently underwent an exploratory laparotomy and right salpingectomy for a suspected ectopic pregnancy. The postoperative period was uneventful, and the intrauterine pregnancy continued to term.

Conclusion

Heterotopic pregnancy should be included in the differential diagnosis for women presenting with hemoperitoneum even beyond the first trimester.

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Heterotopic pregnancy is the implantation of simultaneous pregnancies at two sites.

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They are normally diagnosed in the first trimester on transvaginal ultrasound.

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We present a case of a heterotopic pregnancy beyond the first trimester.

International gestational age-specific centiles for umbilical artery Doppler indices: a longitudinal prospective cohort study of the INTERGROWTH-21st Project

BACKGROUND

Reference values for umbilical artery Doppler indices are used clinically to assess fetal well-being. However, many studies that have produced reference charts have important methodologic limitations, and these result in significant heterogeneity of reported reference ranges.

OBJECTIVES

To produce international gestational age-specific centiles for umbilical artery Doppler indices based on longitudinal data and the same rigorous methodology used in the original Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project.

STUDY DESIGN

In Phase II of the INTERGROWTH-21st Project (the INTERBIO-21st Study), we prospectively continued enrolling pregnant women according to the same protocol from 3 of the original populations in Pelotas (Brazil), Nairobi (Kenya), and Oxford (United Kingdom) that had participated in the Fetal Growth Longitudinal Study. Women with a singleton pregnancy were recruited at <14 weeks' gestation, confirmed by ultrasound measurement of crown-rump length, and then underwent standardized ultrasound every 5±1 weeks until delivery. From 22 weeks of gestation umbilical artery indices (pulsatility index, resistance index, and systolic/diastolic ratio) were measured in a blinded fashion, using identical equipment and a rigorously standardized protocol. Newborn size at birth was assessed using the international INTERGROWTH-21st Standards, and infants had detailed assessment of growth, nutrition, morbidity, and motor development at 1 and 2 years of age. The appropriateness of pooling data from the 3 study sites was assessed using variance component analysis and standardized site differences. Umbilical artery indices were modeled as functions of the gestational age using an exponential, normal distribution with second-degree fractional polynomial smoothing; goodness of fit for the overall models was assessed.

RESULTS

Of the women enrolled at the 3 sites, 1629 were eligible for this study; 431 (27%) met the entry criteria for the construction of normative centiles, similar to the proportion seen in the original fetal growth longitudinal study. They contributed a total of 1243 Doppler measures to the analysis; 74% had 3 measures or more. The healthy low-risk status of the population was confirmed by the low rates of preterm birth (4.9%) and preeclampsia (0.7%). There were no neonatal deaths and satisfactory growth, health, and motor development of the infants at 1 and 2 years of age were documented. Only a very small proportion (2.8%-6.5%) of the variance of Doppler indices was due to between-site differences; in addition, standardized site difference estimates were marginally outside this threshold in only 1 of 27 comparisons, and this supported the decision to pool data from the 3 study sites. All 3 Doppler indices decreased with advancing gestational age. The 3rd, 5th 10th, 50th, 90th, 95th, and 97th centiles according to gestational age for each of the 3 indices are provided, as well as equations to allow calculation of any value as a centile and z scores. The mean pulsatility index according to gestational age = 1.02944 + 77.7456*(gestational age)-2 - 0.000004455*gestational age3.

CONCLUSION

We present here international gestational age-specific normative centiles for umbilical artery Doppler indices produced by studying healthy, low-risk pregnant women living in environments with minimal constraints on fetal growth. The centiles complement the existing INTERGROWTH-21st Standards for assessment of fetal well-being.

Expected-value bias in routine third-trimester growth scans

OBJECTIVES

Operators performing fetal growth scans are usually aware of the gestational age of the pregnancy, which may lead to expected-value bias when performing biometric measurements. We aimed to evaluate the incidence of expected-value bias in routine fetal growth scans and assess its impact on standard biometric measurements.

METHODS

We collected prospectively full-length video recordings of routine ultrasound growth scans coupled with operator eye tracking. Expected value was defined as the gestational age at the time of the scan, based on the estimated due date that was established at the dating scan. Expected-value bias was defined as occurring when the operator looked at the measurement box on the screen during the process of caliper adjustment before saving a measurement. We studied the three standard biometric planes on which measurements of head circumference (HC), abdominal circumference (AC) and femur length (FL) are obtained. We evaluated the incidence of expected-value bias and quantified the impact of biased measurements.

RESULTS

We analyzed 272 third-trimester growth scans, performed by 16 operators, during which a total of 1409 measurements (354 HC, 703 AC and 352 FL; including repeat measurements) were obtained. Expected-value bias occurred in 91.4% of the saved standard biometric plane measurements (85.0% for HC, 92.9% for AC and 94.9% for FL). The operators were more likely to adjust the measurements towards the expected value than away from it (47.7% vs 19.7% of measurements; P < 0.001). On average, measurements were corrected by 2.3 ± 5.6, 2.4 ± 10.4 and 3.2 ± 10.4 days of gestation towards the expected gestational age for the HC, AC, and FL measurements, respectively. Additionally, we noted a statistically significant reduction in measurement variance once the operator was biased (P = 0.026). Comparing the lowest and highest possible estimated fetal weight (using the smallest and largest biased HC, AC and FL measurements), we noted that the discordance, in percentage terms, was 10.1% ± 6.5%, and that in 17% (95% CI, 12-21%) of the scans, the fetus could be considered as small-for-gestational age or appropriate-for-gestational age if using the smallest or largest possible measurements, respectively. Similarly, in 13% (95% CI, 9-16%) of scans, the fetus could be considered as large-for-gestational age or appropriate-for-gestational age if using the largest or smallest possible measurements, respectively.

CONCLUSIONS

During routine third-trimester growth scans, expected-value bias frequently occurs and significantly changes standard biometric measurements obtained. © 2019 the Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Expected-value bias: is it time to remove features from ultrasound machines?

Linked Comment: Ultrasound Obstet Gynecol 2020; 55:375-382.