Ultrasound dating at 12-14 weeks of gestation. A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies

Machine Learning Assessment of Gestational Age in Accelerated Maturation, Delayed Maturation, Villous Edema, Chorangiosis, and Intrauterine Fetal Demise

CONTEXT.—

Assessment of placental villous maturation is among the most common tasks in perinatal pathology. However, the significance of abnormalities in morphology is unclear and interobserver variability is significant.

OBJECTIVE.—

To develop a machine learning model of placental maturation across the second and third trimesters and quantify the impact of different pathologist-diagnosed abnormalities of villous morphology.

DESIGN.—

Digitize placental villous slides from more than 2500 placentas at 12.0 to 42.6 weeks. Build whole slide learning models to estimate obstetrician-determined gestational age for cases with appropriate maturation and normal morphology. Define the model output as "placental age" and compare it to the chronologic gestational age.

RESULTS.—

Our model showed an r2 of 0.864 and mean absolute error of 1.62 weeks for placentas with appropriate maturation in the test set. Pathologist diagnosis of accelerated maturation was associated with a 2.56-week increase in placental age (±2.91 weeks, P < .001), while delayed maturation was associated with a 0.92-week decrease in placental age (±1.82 weeks, P < .001). Intrauterine fetal demise causes diverse changes to placental age, driven by the nature of the demise. We tested the impact of training a model, using all live births. The resulting r2 was 0.874 and mean absolute error was 1.73 weeks. Furthermore, by including cases with abnormal maturation in the training data, the effect size of accelerated maturation was blunted to only 0.56 ± 2.35 weeks (P < .001).

CONCLUSIONS.—

We show that various abnormalities of villous maturation and morphology correlate with abnormalities in placental age. This "no pathologist" model could be useful in situations where pathologists are unavailable or the need for consistency outweighs the utility of expertise.

Biparietal diameter for first-trimester pregnancy dating: multicenter cohort study

OBJECTIVE

To evaluate the accuracy of fetal biparietal diameter (BPD) measurement in comparison with crown-rump length (CRL) measurement for pregnancy dating at 11-13 weeks' gestation.

METHODS

This was a retrospective multicenter cohort study performed in five maternity units in Spain, the UK, Belgium and Bulgaria between January 2011 and December 2019. We included all women who attended a routine ultrasound examination at 11 + 0 to 13 + 6 weeks who had a singleton pregnancy with a viable non-malformed fetus/neonate and ultrasound-derived measurements for both CRL and BPD, along with a comprehensive record of pregnancy outcomes. We developed a formula for pregnancy dating based on BPD using data from pregnancies conceived via in-vitro fertilization (IVF) by applying a simple linear regression. We validated this formula both internally and externally and compared it with the most commonly used formulae (Robinson's CRL-based and Kustermann's BPD-based formulae) through utilization of the Euclidean distance, relative absolute error and mean squared error. We also examined the rate of induction of labor for post-term pregnancy based on dating using each of the formulae.

RESULTS

A total of 49 492 women were included in the study, comprising 47 223 (95.4%) who conceived spontaneously and 2269 (4.6%) who conceived via IVF. In the internal validation performed using data from IVF pregnancies, our newly developed formula showed no significant difference when compared with the true gestational age calculated using conception date, with a mean difference of 0.0006 (95% CI, -0.09 to 0.09) days. In contrast, the mean difference of Kustermann's BPD-based formula was -0.31 (95% CI, -0.46 to -0.17) days and the mean difference of Robinson's CRL-based formula was -1.78 (95% CI, -1.88 to -1.68) days. In the external validation using data from spontaneously conceived pregnancies, with dating using Robinson's formula as the reference for 'true' gestational age, both our formula and Kustermann's formula resulted in underestimation of gestational age, with significant mean differences of -1.25 (95% CI, -1.28 to -1.22) days and -0.96 (95% CI, -0.98 to -0.93) days, respectively. The largest differences compared with Robinson's formula-based dating results were observed between 11 + 0 and 12 + 0 weeks. Dating the pregnancy using Robinson's formula led to 8.1% of pregnancies identified as requiring induction after 41 + 3 weeks, compared with 6.8% (P < 0.001) and 7.0% (P < 0.001) when applying our formula and Kustermann's formula, respectively.

CONCLUSION

Pregnancy dating based on ultrasound measurement of fetal BPD between 11 + 0 and 13 + 6 weeks' gestation is a reliable alternative to dating based on fetal CRL. © 2025 International Society of Ultrasound in Obstetrics and Gynecology.

Novel sonographic reference charts for early pregnancy based on known gestational age

Objective

To study pregnancy dating, we developed growth charts using data from pregnancies with known gestational age. The most widely used growth charts for ultrasonographic early pregnancy variables were developed decades ago and are based on dating by the last menstrual period. The aims of the study were to create growth charts for early pregnancy (including crown-rump length, gestational sac diameter, yolk sac diameter, and amniotic cavity diameter) for last menstrual period-dated spontaneous pregnancies and pregnancies conceived through assisted reproductive technology (ART) with known gestational age; and to compare crown-rump length measurements with two established traditional charts based on last menstrual period dating.

Design

Retrospective cohort study.

Subjects

Of 1,061 singletons, 2,803 crown-rump length measurements from 716 exactly dated ART gestations with 1,143 crown-rump length measurements from 345 spontaneous pregnancies, which were dated by the last menstrual period in women with regular cycles, were compared using nonlinear quantile regression.

Exposure

A total of 716 ART pregnancies and 345 spontaneous pregnancies underwent ultrasound examinations, with a median of four visits at various points during the first trimester.

Main Outcome Measures

Early pregnancy dating with growth charts based on crown-rump length, gestational sac-, yolk sac- and amniotic cavity diameter.

Results

Novel reference charts for ultrasound dating of gestational age based on crown-rump length from 4 + 6 to 10 + 6 gestational weeks were created. The difference of the 10th and 90th percentile was significantly higher in spontaneous compared with ART pregnancies (P<.05). For the same crown-rump length, the gestational age of spontaneous pregnancies was estimated to be up to 4.08 days older than in ART pregnancies at the 90th percentile. Preexisting curves (Robinson/Fleming, Hadlock) aligned closely with the new reference curve mid-range but showed larger deviations at the extremes of assessed gestational ages.

Conclusion

Early pregnancy crown-rump length curves based on last menstrual period may overestimate gestational age. Using 2,803 crown-rump length measurements, we propose the current comprehensive charts for early pregnancy within a population with known gestational age for crown-rump length, gestational sac diameter, yolk sac diameter, and amniotic cavity diameter.

An analytical cross-sectional study: determining gestational age using fetal clavicle length during the second trimester

PURPOSE

To investigate the correlation between fetal clavicle length and gestational age in pregnant patients from 14 and 27 weeks of gestation.

METHODS

This was a retrospective cross-sectional study of patients from 14 and 27 weeks of gestation. Ultrasonographic measurements such as abdominal circumference (AC), femur length (FL), humerus length (HL), clavicle length (CL), head circumference (HC), biparietal diameter (BPD), estimated fetal weight (EFW), and transverse cerebellum diameter (TCD) were made and compared.

RESULTS

A total of 552 patients were evaluated in our clinic and CL was measured properly and successfully in all fetuses. Fetal AC, FL, HL, CL, BPD, HC, EFW and TCD measurements were significantly and strongly correlated with gestational week, and Pearson's correlation values were 0.964, 0.965, 0.959, 0.965, 0.951, 0.917, 0.925, and 0.954, respectively (p < 0.001). In the regression analysis equation, gestational week = 0.894 + CL × 0.961.

CONCLUSION

There was a significant positive correlation between fetal CL (mm) and gestational week. We suggest that the 1 mm = 1 week rule can be used for patients with anomalies of the cerebellum and vermis, as well as for patients with unknown last menstrual period.

Automated quantitative evaluation of fetal atrioventricular annular plane systolic excursion before and after intrauterine blood transfusion in pregnancies affected by red blood cell alloimmunization

INTRODUCTION

Maternal red blood cell alloimmunization during pregnancy can lead to hemolysis and various degrees of fetal anemia, which can be treated with intrauterine blood transfusion (IUT) to prevent adverse outcomes. Knowledge about fetal myocardial function and adaptation is limited. The aim of the present study was to measure fetal atrioventricular plane displacement before and after IUT and compare these measurements with previously established reference ranges.

MATERIAL AND METHODS

An observational study was conducted on pregnant women affected by red blood cell alloimmunization. Fetal echocardiography was performed before and after IUT. The atrioventricular plane displacement of the left and right ventricular walls and interventricular septum, described as mitral, septal, and tricuspid annular plane systolic excursion (MAPSE, SAPSE, and TAPSE, respectively), was assessed using color tissue Doppler imaging with automated analysis software. A Mann-Whitney U test was used to compare the z scores to the normal mean before and after IUT.

RESULTS

Twenty-seven fetuses were included. The mean z score for pre-IUT MAPSE was significantly increased compared with the reference ranges, +0.46 (95% confidence interval [CI] +0.17 to +0.75; p = 0.039), while the mean z scores for post-IUT SAPSE and TAPSE were significantly decreased, -0.65 (95% CI -1.11 to -0.19; p < 0.001) and -0.60 (95% CI -1.04 to -0.17; p = 0.003), respectively. The difference in atrioventricular plane displacement z scores before and after IUT was statistically significant in all three locations. The median difference between the pre-IUT and post-IUT z scores was -0.66 (95% CI -1.03 to -0.33, p < 0.001) for MAPSE, -1.05 (95% CI -1.43 to -0.61, p < 0.001) for SAPSE, and -0.60 (95% CI -1.19 to -0.01, p = 0.046) for TAPSE.

CONCLUSIONS

This study suggests that atrioventricular plane displacement, when determined using automated analysis software, may represent a quantitative parameter, describing fetal myocardial function and adaptation before and after IUT.

Variability of bovine conceptus-related volumes in early pregnancy measured with transrectal three-dimensional ultrasonography

Up until now, bovine fetometry has been entirely based on 2-dimensional ultrasonography. Fetal size is estimated by several linear measurements such as crown-rump length (CRL). However, the advent of 3-dimensional ultrasonography (3D-US) provides in vivo access to the volumes of the fetus and its amniotic sac. The objective of this preliminary observational study was to determine the variability of conceptus-related volumes using transrectal 3D-US in dairy cows and to identify factors affecting them. Furthermore, relationships between the gained measurements and calf birth weight were investigated. In total, 315 Simmental and Holstein-Friesian dairy cows were transrectally examined at d 42 after breeding using a portable ultrasound device (Voluson I, GE Healthcare). Gestational volumes including fetal volume (FV) and amniotic sac volume (ASV) were determined with the software tool VOCAL (Virtual Organ Computer-Aided Analysis, GE Healthcare), whereas amniotic fluid volume (AFV) values were derived from the subtraction of FV from ASV. The CRL was determined by means of 3-dimensional data. The mean values and standard deviations for FV, ASV, AFV, and CRL were 1.47 ± 0.25 cm³, 5.86 ± 1.22 cm³, 4.38 ± 1.02 cm³, and 2.38 ± 0.18 cm, respectively. All gestational volumes and CRL values were affected by breed. In Simmental cattle, larger concepti were observed compared with pregnancies derived from Holstein-Friesian animals. Parity affected only ASV and AFV, with heifers showing greater values than lactating cows. The CRL was positively associated with milk protein content. It was not possible to predict calf weight at birth by using FV, ASV, or AFV; however, tendencies were found for ASV and AFV. The present study was the first to adopt 3D-US volumetry to assess early pregnancy development in dairy cattle. Our results showed that this method could be used successfully to identify minor variations in conceptus growth.

Neonatal Outcome and Treatment Perspectives of Preterm Infants at the Border of Viability

Decision-making at the border of viability remains challenging for the expectant parents and the medical team. The preterm infant is dependent on others making the decision that will impact them for a lifetime in hopefully their best interest. Besides survival and survival without neurodevelopmental impairment, other relevant outcome measures, such as the quality of life of former preterm infants and the impact on family life, need to be integrated into prenatal counselling. Recommendations and national guidelines continue to rely on arbitrarily set gestational age limits at which treatment is not recommended, can be considered and it is recommended. These guidelines neglect other individual prognostic outcome factors like antenatal steroids, birth weight and gender. Besides individual factors, centre-specific factors like perinatal treatment intensity and the attitude of healthcare professionals significantly determine the futures of these infants at the border of viability. A more comprehensive approach regarding treatment recommendations and relevant outcome measures is necessary.

Using AMANHI-ACT cohorts for external validation of Iowa new-born metabolic profiles based models for postnatal gestational age estimation

BACKGROUND

Globally, 15 million infants are born preterm and another 23.2 million infants are born small for gestational age (SGA). Determining burden of preterm and SGA births, is essential for effective planning, modification of health policies and targeting interventions for reducing these outcomes for which accurate estimation of gestational age (GA) is crucial. Early pregnancy ultrasound measurements, last menstrual period and post-natal neonatal examinations have proven to be not feasible or inaccurate. Proposed algorithms for GA estimation in western populations, based on routine new-born screening, though promising, lack validation in developing country settings. We evaluated the hypothesis that models developed in USA, also predicted GA in cohorts of South Asia (575) and Sub-Saharan Africa (736) with same precision.

METHODS

Dried heel prick blood spots collected 24-72 hours after birth from 1311 new-borns, were analysed for standard metabolic screen. Regression algorithm based, GA estimates were computed from metabolic data and compared to first trimester ultrasound validated, GA estimates (gold standard).

RESULTS

Overall Algorithm (metabolites + birthweight) estimated GA to within an average deviation of 1.5 weeks. The estimated GA was within the gold standard estimate by 1 and 2 weeks for 70.5% and 90.1% new-borns respectively. Inclusion of birthweight in the metabolites model improved discriminatory ability of this method, and showed promise in identifying preterm births. Receiver operating characteristic (ROC) curve analysis estimated an area under curve of 0.86 (conservative bootstrap 95% confidence interval (CI) = 0.83 to 0.89); P < 0.001) and Youden Index of 0.58 (95% CI = 0.51 to 0.64) with a corresponding sensitivity of 80.7% and specificity of 77.6%.

CONCLUSION

Metabolic gestational age dating offers a novel means for accurate population-level gestational age estimates in LMIC settings and help preterm birth surveillance initiatives. Further research should focus on use of machine learning and newer analytic methods broader than conventional metabolic screen analytes, enabling incorporation of region-specific analytes and cord blood metabolic profiles models predicting gestational age accurately.

Guideline No. 388-Determination of Gestational Age by Ultrasound

OBJECTIVE

To assist clinicians in assigning gestational age based on ultrasound biometry.

OUTCOMES

To determine whether ultrasound dating provides more accurate gestational age assessment than menstrual dating with or without the use of ultrasound. To provide maternity health care providers and researchers with evidence-based guidelines for the assignment of gestational age. To determine which ultrasound biometric parameters are superior when gestational age is uncertain. To determine whether ultrasound gestational age assessment is cost effective.

EVIDENCE

Published literature was retrieved through searches of PubMed or MEDLINE and The Cochrane Library in 2013 using appropriate controlled vocabulary and key words (gestational age, ultrasound biometry, ultrasound dating). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies written in English. There were no date restrictions. Searches were updated on a regular basis and incorporated in the guideline to July 31, 2013. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

Accurate assignment of gestational age may reduce post-dates labour induction and may improve obstetric care through allowing the optimal timing of necessary interventions and the avoidance of unnecessary ones. More accurate dating allows for optimal performance of prenatal screening tests for aneuploidy. A national algorithm for the assignment of gestational age may reduce practice variations across Canada for clinicians and researchers. Potential harms include the possible reassignment of dates when significant fetal pathology (such as fetal growth restriction or macrosomia) result in a discrepancy between ultrasound biometric and clinical gestational age. Such reassignment may lead to the omission of appropriate-or the performance of inappropriate-fetal interventions.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Automated analysis of fetal cardiac function using color tissue Doppler imaging

OBJECTIVE

To evaluate the feasibility of automated analysis of fetal myocardial velocity recordings obtained by color tissue Doppler imaging (cTDI).

METHODS

This was a prospective cross-sectional observational study of 107 singleton pregnancies ≥ 41 weeks of gestation. Myocardial velocity recordings were obtained by cTDI in a long-axis four-chamber view of the fetal heart. Regions of interest were placed in the septum and the right (RV) and left (LV) ventricular walls at the level of the atrioventricular plane. Peak myocardial velocities and mechanical cardiac time intervals were measured both manually and by an automated algorithm and agreement between the two methods was evaluated.

RESULTS

In total, 321 myocardial velocity traces were analyzed using each method. It was possible to analyze all velocity traces obtained from the LV, RV and septal walls with the automated algorithm, and myocardial velocities and cardiac mechanical time intervals could be measured in 96% of all traces. The same results were obtained when the algorithm was run repeatedly. The myocardial velocities measured using the automated method correlated significantly with those measured manually. The agreement between methods was not consistent and some cTDI parameters had considerable bias and poor precision.

CONCLUSIONS

Automated analysis of myocardial velocity recordings obtained by cTDI was feasible, suggesting that this technique could simplify and facilitate the use of cTDI in the evaluation of fetal cardiac function, both in research and in clinical practice. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Discrepancy between pregnancy dating methods affects obstetric and neonatal outcomes: a population-based register cohort study

To assess associations between discrepancy of pregnancy dating methods and adverse pregnancy, delivery, and neonatal outcomes, odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for discrepancy categories among all singleton births from the Medical Birth Register (1995-2010) with estimated date of delivery (EDD) by last menstrual period (LMP) minus EDD by ultrasound (US) -20 to +20 days. Negative/positive discrepancy was a fetus smaller/larger than expected when dated by US (EDD postponed/changed to an earlier date). Large discrepancy was <10^th or >90^th percentile. Reference was median discrepancy ±2 days. Odds for diabetes and preeclampsia were higher in pregnancies with negative discrepancy, and for most delivery outcomes in case of large positive discrepancy (+9 to +20 days): shoulder dystocia [OR 1.16 (95% CI 1.01-1.33)] and sphincter injuries [OR 1.13 (95% CI 1.09-1.17)]. Odds for adverse neonatal outcomes were higher in large negative discrepancy (-4 to -20 days): low Apgar score [OR 1.18 (95% CI 1.09-1.27)], asphyxia [OR 1.18 (95% CI 1.11-1.25)], fetal death [OR 1.47 (95% CI 1.32-1.64)], and neonatal death [OR 2.19 (95% CI 1.91-2.50)]. In conclusion, especially, large negative discrepancy was associated with increased risks of adverse perinatal outcomes.

A proteomic clock of human pregnancy

BACKGROUND

Early detection of maladaptive processes underlying pregnancy-related pathologies is desirable because it will enable targeted interventions ahead of clinical manifestations. The quantitative analysis of plasma proteins features prominently among molecular approaches used to detect deviations from normal pregnancy. However, derivation of proteomic signatures sufficiently predictive of pregnancy-related outcomes has been challenging. An important obstacle hindering such efforts were limitations in assay technology, which prevented the broad examination of the plasma proteome.

OBJECTIVE

The recent availability of a highly multiplexed platform affording the simultaneous measurement of 1310 plasma proteins opens the door for a more explorative approach. The major aim of this study was to examine whether analysis of plasma collected during gestation of term pregnancy would allow identifying a set of proteins that tightly track gestational age. Establishing precisely timed plasma proteomic changes during term pregnancy is a critical step in identifying deviations from regular patterns caused by fetal and maternal maladaptations. A second aim was to gain insight into functional attributes of identified proteins and link such attributes to relevant immunological changes.

STUDY DESIGN

Pregnant women participated in this longitudinal study. In 2 subsequent sets of 21 (training cohort) and 10 (validation cohort) women, specific blood specimens were collected during the first (7-14 weeks), second (15-20 weeks), and third (24-32 weeks) trimesters and 6 weeks postpartum for analysis with a highly multiplexed aptamer-based platform. An elastic net algorithm was applied to infer a proteomic model predicting gestational age. A bootstrapping procedure and piecewise regression analysis was used to extract the minimum number of proteins required for predicting gestational age without compromising predictive power. Gene ontology analysis was applied to infer enrichment of molecular functions among proteins included in the proteomic model. Changes in abundance of proteins with such functions were linked to immune features predictive of gestational age at the time of sampling in pregnancies delivering at term.

RESULTS

An independently validated model consisting of 74 proteins strongly predicted gestational age (P = 3.8 × 10^-14, R = 0.97). The model could be reduced to 8 proteins without losing its predictive power (P = 1.7 × 10^-3, R = 0.91). The 3 top ranked proteins were glypican 3, chorionic somatomammotropin hormone, and granulins. Proteins activating the Janus kinase and signal transducer and activator of transcription pathway were enriched in the proteomic model, chorionic somatomammotropin hormone being the top-ranked protein. Abundance of chorionic somatomammotropin hormone strongly correlated with signal transducer and activator of transcription-5 signaling activity in CD4 T cells, the endogenous cell-signaling event most predictive of gestational age.

CONCLUSION

Results indicate that precisely timed changes in the plasma proteome during term pregnancy mirror a proteomic clock. Importantly, the combined use of several plasma proteins was required for accurate prediction. The exciting promise of such a clock is that deviations from its regular chronological profile may assist in the early diagnoses of pregnancy-related pathologies, and point to underlying pathophysiology. Functional analysis of the proteomic model generated the novel hypothesis that chrionic somatomammotropin hormone may critically regulate T-cell function during pregnancy.

Caring for Families at the Limits of Viability: The Education of Dr Green

Resuscitation decisions for infants born at the edges of viability are complicated moral dilemmas, and the process of making these decisions is emotionally exhausting and morally distressful for families and physicians alike. An ethical approach to making these decisions requires input from physicians and parents; individuals tasked with facilitating such decisions must possess the communication and counseling skills needed to assist families with these painful and life-altering decisions. It is incumbent on all of us to continue our investigation into how we can better assist families in this process while providing care that is in their best interest.

Committee Opinion No 700: Methods for Estimating the Due Date

Accurate dating of pregnancy is important to improve outcomes and is a research and public health imperative. As soon as data from the last menstrual period, the first accurate ultrasound examination, or both are obtained, the gestational age and the estimated due date (EDD) should be determined, discussed with the patient, and documented clearly in the medical record. Subsequent changes to the EDD should be reserved for rare circumstances, discussed with the patient, and documented clearly in the medical record. A pregnancy without an ultrasound examination that confirms or revises the EDD before 22 0/7 weeks of gestational age should be considered suboptimally dated. When determined from the methods outlined in this document for estimating the due date, gestational age at delivery represents the best obstetric estimate for the purpose of clinical care and should be recorded on the birth certificate. For the purposes of research and surveillance, the best obstetric estimate, rather than estimates based on the last menstrual period alone, should be used as the measure for gestational age.

Lower accuracy in prediction of delivery date in Stockholm County following introduction of new guidelines

INTRODUCTION

In Stockholm County, new guidelines for predicting the day of delivery were introduced in 2010. Recent clinical use has indicated that the predictive quality might be suboptimal. This study compares the accuracy of three equations applied during the first (crown-rump length or bi-parietal diameter) and second trimesters (bi-parietal diameter or bi-parietal diameter combined with femur length).

MATERIAL AND METHODS

The accuracy of estimated delivery date was compared in 14 239 ultrasound exams using median deviations from actual birth date, proportion of postterms, births within ±seven days of estimated delivery date, accuracy variations depending on fetal size, alternative fetal measurements obtained on the same occasion, and menstrual age.

RESULTS

The bi-parietal diameter and crown-rump length formulae overestimated pregnancy length by two and three days respectively, causing 7-8% of pregnancies to be labelled postterm. A combined bi-parietal diameter+femur length formula overestimated by one day, with 5.1% postterms. No significant difference was found in the proportion of births within ±seven days. Second trimester estimated delivery date assessment had larger median variations than did first trimester assessment and suffered from shifting deviations across fetal size. The comparison of different biometry formulae in the same individual demonstrated one day extra deviation for bi-parietal diameter and three days extra deviation for crown-rump length compared with the combined bi-parietal diameter+femur length formula.

CONCLUSIONS

The algorithms and dating occasions tested seem inappropriate for the present 280-day term definition. Alternative formulae ought to be sought, and the assumed duration of pregnancy reconsidered; 283 days corresponds to the observed pregnancy length calculated from last menstrual period, and would better fit the observed results for first trimester ultrasound scans.

Détermination de l'âge gestationnel par échographie

OBJECTIF

Aider les cliniciens à attribuer un âge gestationnel en fonction des résultats de la biométrie échographique.

ISSUES

Déterminer si la datation par échographie offre une évaluation plus précise de l'âge gestationnel que la datation en fonction des dernières règles avec ou sans recours à l'échographie. Offrir, aux praticiens et aux chercheurs du domaine des soins de maternité, des lignes directrices factuelles en matière d'attribution de l'âge gestationnel. Identifier les paramètres biométriques échographiques qui sont de fiabilité supérieure lorsque l'âge gestationnel est incertain. Déterminer la rentabilité de l'évaluation de l'âge gestationnel par échographie. RéSULTATS: La littérature publiée a été récupérée par l'intermédiaire de recherches menées dans PubMed ou MEDLINE et The Cochrane Library en 2013 au moyen d'un vocabulaire contrôlé et de mots clés appropriés (p. ex. « gestational age », « ultrasound biometry » et « ultrasound dating »). Les résultats ont été restreints aux analyses systématiques, aux essais comparatifs randomisés / essais cliniques comparatifs et aux études observationnelles rédigés en anglais. Aucune restriction n'a été appliquée en matière de dates. Les recherches ont été mises à jour de façon régulière et intégrées à la directive clinique jusqu'au 31 juillet 2013. La littérature grise (non publiée) a été identifiée par l'intermédiaire de recherches menées dans les sites Web d'organismes s'intéressant à l'évaluation des technologies dans le domaine de la santé et d'organismes connexes, dans des collections de directives cliniques, dans des registres d'essais cliniques et auprès de sociétés de spécialité médicale nationales et internationales.

VALEURS

La qualité des résultats est évaluée au moyen des critères décrits dans le rapport du Groupe d'étude canadien sur les soins de santé préventifs (Tableau 1). AVANTAGES, DéSAVANTAGES ET COûTS: L'attribution précise d'un âge gestationnel pourrait réduire l'incidence du déclenchement mené en raison d'une grossesse prolongée et améliorer les soins obstétricaux en nous permettant de planifier la chronologie des interventions nécessaires de façon optimale et d'éviter les interventions inutiles. Une datation plus précise permet l'optimisation de la tenue de tests prénataux de dépistage de l'aneuploïdie. Un algorithme national d'attribution de l'âge gestationnel pourrait atténuer les variations pancanadiennes en matière de pratique pour les cliniciens et les chercheurs. Parmi les désavantages potentiels, on trouve la réattribution possible des dates lorsqu'une pathologie fœtale importante (comme le retard de croissance intra-utérin ou la macrosomie) donne lieu à une divergence entre les résultats de la biométrie échographique et l'âge gestationnel clinique. Une telle réattribution pourrait mener à l'omission d'interventions fœtales justifiées ou à la tenue d'interventions fœtales injustifiées. DéCLARATIONS SOMMAIRES: RECOMMANDATIONS.

First-trimester reference centiles of fetal biometry in Indian population

AIM AND OBJECTIVE

To create crown-rump length (CRL)-based biometric chart for fetus in the first trimester among the Indian population.

MATERIAL AND METHODS

Cross-sectional data were obtained from 400 singleton pregnancies between 11 and 14 weeks gestation with a normal outcome. Linear regression models were constructed; the mean and SD were derived as a function of CRL.

RESULTS

There was a positive correlation of CRL with nuchal translucency (NT) (y = 0.0102x + 0.6307 R²=0.1177), biparietal diameter (BPD) (BPD = 0.032*CRL +0.185 R²=0.765), occipito-frontal diameter (OFD), lateral ventricular diameter (LV), abdominal circumference (AC) (AC = 0.944*CRL +9.684 R²=0.668), femur length (FL) (FL = 0.222*CRL -4.734 R²=0.661), fetal weight (FW) (FW = 1.328*CRL -10.41 R²=0.662). The regression models and centile charts of NT, BPD, OFD, LV, AC, and FW were constructed. Taking FW as the independent variable, a linear equation of BPD, AC, and FL to calculate weight was constructed.

CONCLUSIONS

The first-trimester centile charts of fetal parameters can be used as a reference for Indian population in the determination of gestational age or other adverse outcomes.

Fetal growth is associated with first-trimester maternal vascular function

OBJECTIVE

To investigate the relationship between maternal endothelial function in the first trimester, assessed in both the brachial artery and the forearm skin microcirculation, and fetal growth.

METHODS

Vascular function was assessed in 56 pregnant women during gestational weeks 11-14. Vascular reactivity in the brachial artery was evaluated by postischemic hyperemia-induced flow-mediated vasodilatation (FMD) and by vasodilatation following administration of sublingual glyceryl trinitrate (GTN). Forearm skin microcirculation was investigated by laser Doppler perfusion imaging during iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) to assess endothelium-dependent and -independent microvascular vasodilatation, respectively. Fetal growth was measured at study inclusion and birth-weight centile was calculated after delivery.

RESULTS

FMD and GTN-induced vasodilatation were both associated with birth-weight centile. On multivariate analysis (adjusted for brachial artery diameter at rest, blood pressure, maternal age and heart rate), for FMD β = 1.7 (95% CI, 0.06-3.34), r²  = 0.26 and P = 0.042, and for GTN-induced vasodilatation β = 2.6 (95% CI, 0.44-4.68), r²  = 0.15 and P = 0.02. Endothelium-dependent and -independent microvascular reactivity were also associated with birth-weight centile: for ACh β = 7.82 (95% CI, 1.81-13.83), r²  = 0.12 and P = 0.029, and for SNP β = 6.27 (95% CI, 1.20-11.34), r²  = 0.11 and P = 0.016.

CONCLUSION

First-trimester maternal vascular dilatation capacity (rather than endothelial function alone) is associated with fetal growth. These findings were consistent in both the brachial artery and the forearm skin microcirculation. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Gestational dating by metabolic profile at birth: a California cohort study

BACKGROUND

Accurate gestational dating is a critical component of obstetric and newborn care. In the absence of early ultrasound, many clinicians rely on less accurate measures, such as last menstrual period or symphysis-fundal height during pregnancy, or Dubowitz scoring or the Ballard (or New Ballard) method at birth. These measures often underestimate or overestimate gestational age and can lead to misclassification of babies as born preterm, which has both short- and long-term clinical care and public health implications.

OBJECTIVE

We sought to evaluate whether metabolic markers in newborns measured as part of routine screening for treatable inborn errors of metabolism can be used to develop a population-level metabolic gestational dating algorithm that is robust despite intrauterine growth restriction and can be used when fetal ultrasound dating is not available. We focused specifically on the ability of these markers to differentiate preterm births (PTBs) (<37 weeks) from term births and to assign a specific gestational age in the PTB group.

STUDY DESIGN

We evaluated a cohort of 729,503 singleton newborns with a California birth in 2005 through 2011 who had routine newborn metabolic screening and fetal ultrasound dating at 11-20 weeks' gestation. Using training and testing subsets (divided in a ratio of 3:1) we evaluated the association among PTB, target newborn characteristics, acylcarnitines, amino acids, thyroid-stimulating hormone, 17-hydroxyprogesterone, and galactose-1-phosphate-uridyl-transferase. We used multivariate backward stepwise regression to test for associations and linear discriminate analyses to create a linear function for PTB and to assign a specific week of gestation. We used sensitivity, specificity, and positive predictive value to evaluate the performance of linear functions.

RESULTS

Along with birthweight and infant age at test, we included 35 of the 51 metabolic markers measured in the final multivariate model comparing PTBs and term births. Using a linear discriminate analyses-derived linear function, we were able to sort PTBs and term births accurately with sensitivities and specificities of ≥95% in both the training and testing subsets. Assignment of a specific week of gestation in those identified as PTBs resulted in the correct assignment of week ±2 weeks in 89.8% of all newborns in the training and 91.7% of those in the testing subset. When PTB rates were modeled using the metabolic dating algorithm compared to fetal ultrasound, PTB rates were 7.15% vs 6.11% in the training subset and 7.31% vs 6.25% in the testing subset.

CONCLUSION

When considered in combination with birthweight and hours of age at test, metabolic profile evaluated within 8 days of birth appears to be a useful measure of PTB and, among those born preterm, of specific week of gestation ±2 weeks. Dating by metabolic profile may be useful in instances where there is no fetal ultrasound due to lack of availability or late entry into care.

Ultrasound screening: Status of markers and efficacy of screening for structural abnormalities

Aneuploidy is a major cause of perinatal morbidity and mortality and can have a significant impact on expecting parents and their families. With early screening and diagnosis it is important to be able to educate parents regarding the potential impact of the diagnosis. This knowledge allows parents the opportunity to consider management options early in the pregnancy, permitting more time to mentally and emotionally prepare both for the course of the pregnancy, and after the birth of the child should the pregnancy continue. Prenatal screening provides pregnant women a non-invasive risk assessment for the most common aneuploidies. Those who are considered "high-risk" then have the option for additional diagnostic (invasive) testing. Prior to the 1980s, prenatal screening consisted of risk assessment through maternal age; however, with the advent of maternal serum biochemical analysis and ultrasound, the field of prenatal screening developed significantly. As biochemical and sonographic advances continued into the 1990s, the emphasis shifted to risk assessment in the first trimester, with the combination of maternal serum analytes and sonographic evaluation of the nuchal translucency.(1) Within the last decade, the introduction of non-invasive screening (NIPT/S) has shown great impact on the expansion and evolving practice of prenatal screening. Although in many places the standard for prenatal testing continues to include maternal serum analytes and sonographic evaluation, the role of each marker alone and in combination remains important. In the era of increasingly available screening tests, especially with NIPT/(NIPS), this article attempts to review the current role of ultrasound in prenatal care and elucidate the role of ultrasound markers in prenatal screening.

Predicting SGA neonates using first-trimester screening: influence of previous pregnancy's birthweight and PAPP-A MoM

OBJECTIVE

Investigating the proportions of anamnestic and biochemical variables of the previous and current pregnancies for the prediction of small for gestational age (SGA) neonates in the current pregnancy.

METHODS

In this observational retrospective study, 45 029 pregnancies were examined, including 3862 patients with more than one pregnancy. Odds ratios for SGA using anamnestic parameters and pregnancy-associated plasma protein A (PAPP-A) values from all pregnancies were estimated by using a logistic regression model.

RESULTS

There were 2552 (5.7%) SGA neonates. Two threshold PAPP-A values were identified at 0.15 MoM and 0.33 MoM with probabilities for SGA of 23% and 17%, respectively. A previous SGA < 10th centile and a current PAPP-A MoM value < 5th centile result in odds ratios of 4.8 (95% CI: 3.5-6.5) and 3.0 (95% CI: 1.8-5.0), respectively. The parameters' combined odds ratio is 14.1 (95% CI: 3.9-50.3) with a number needed to screen of ten for one SGA neonate at a detection rate of 37%.

CONCLUSION

Information on previous pregnancies affected by SGA and a current pregnancy's low PAPP-A value are reliable predictors for a SGA delivery. First-trimester biochemical analysis should be maintained to detect women at risk for delivering a SGA neonate.

Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging workshop

Given that practice variation exists in the frequency and performance of ultrasound and magnetic resonance imaging (MRI) in pregnancy, the Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a workshop to address indications for ultrasound and MRI in pregnancy, to discuss when and how often these studies should be performed, to consider recommendations for optimizing yield and cost effectiveness, and to identify research opportunities. This article is the executive summary of the workshop.

Committee opinion no 611: method for estimating due date

: Accurate dating of pregnancy is important to improve outcomes and is a research and public health imperative. As soon as data from the last menstrual period, the first accurate ultrasound examination, or both are obtained, the gestational age and the estimated due date should be determined, discussed with the patient, and documented clearly in the medical record. Subsequent changes to the estimated due date should be reserved for rare circumstances, discussed with the patient, and documented clearly in the medical record. When determined from the methods outlined in this document for estimating the due date, gestational age at delivery represents the best obstetric estimate for the purpose of clinical care and should be recorded on the birth certificate. For the purposes of research and surveillance, the best obstetric estimate, rather than estimates based on the last menstrual period alone, should be used as the measure for gestational age.

Gestational age and fetal growth assessment among obstetricians

OBJECTIVE

We aimed to characterize gestational age assessment and fetal growth evaluation among obstetricians.

METHODS

Observational, cross-sectional study. We applied a questionnaire to obstetrics specialists and residents, during a national congress on obstetrics.

RESULTS

Almost all 179 respondents correct gestational age in the first trimester by ultrasound, but 63% only if there is a difference of 2-9 days. Ultrasound at 11-13 weeks was considered more accurate than at 8-10 weeks by 81%, with a higher proportion of specialists choosing correctly the last answer (p = 0.05). One-third of the respondents did not correctly point the error associated with the ultrasound estimation of fetal weight (EFW). Of the 88% who use a growth table, only 32% were able to identify it by publication/author. Ninety-eight percent identify fetal growth restriction risk (FGR) with centiles (10th in 76%) and 73% of doctors diagnose FGR without other pathological findings (10th in 49%). 44% finds that a low EFW centile maintenance (4th to 3rd) is more worrisome than the crossing of two quartiles (75th to 24th).

CONCLUSIONS

The role of ultrasound in gestational age assessment and use of EFW use for FGR classification was disparate among participants. EFW and respective centiles may be over relied upon.

Infants of borderline viability: the ethics of delivery room care

For more than half a century neonatologists and ethicists alike have struggled with ethical dilemmas surrounding infants born at the limits of viability. Both doctors and parents face difficult decisions. Do we try to save these babies, knowing that such efforts are likely to be unsuccessful? Or do we provide only comfort care, knowing that, in doing so, you will inevitably allow some babies to die who might have been saved? In this paper, we review the outcome data on these babies and offer ten suggestions for doctors: (1) accept that there is a 'gray zone' during which decisions are not black and white; (2) do not place too much emphasis on gestational age; (3) dying is generally not in an infant's best interest; (4) impairment does not necessarily equal poor quality of life; (5) just because the train has left the station doesn't mean you can't get off; (6) respect powerful emotions; (7) be aware of the self-fulfilling prophecies; (8) time lag likely skews all outcome data; (9) statistics can be both confused and confusing; (10) never abandon parents.

Ultrasound evaluation of the first trimester

Ultrasound is a valuable diagnostic test throughout the first trimester of pregnancy. Early in this trimester, it is used to distinguish between normal intrauterine, failed intrauterine, and ectopic pregnancies. Later it can be used with maternal blood tests to screen for trisomy 21 and other forms of aneuploidy, and in some centers to assess fetal anatomy and diagnose structural anomalies. First trimester sonography is also useful for accurate assessment of gestational age. This article reviews these applications, the approach to establishing diagnoses, and ways to avoid diagnostic mistakes that can lead to serious errors in patient management and adverse pregnancy outcome.

Fetal imaging: Executive summary of a Joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging Workshop

Given that practice variation exists in the frequency and performance of ultrasound and magnetic resonance imaging in pregnancy, the Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a workshop to address indications for ultrasound and magnetic resonance imaging in pregnancy, to discuss when and how often these studies should be performed, to consider recommendations for optimizing yield and cost-effectiveness and to identify research opportunities. This article is the executive summary of the workshop.

Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging Workshop

Given that practice variation exists in the frequency and performance of ultrasound and magnetic resonance imaging (MRI) in pregnancy, the Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a workshop to address indications for ultrasound and MRI in pregnancy, to discuss when and how often these studies should be performed, to consider recommendations for optimizing yield and cost effectiveness, and to identify research opportunities. This article is the executive summary of the workshop.

End-of-life decisions for extremely low-gestational-age infants: why simple rules for complicated decisions should be avoided

Interventions for extremely preterm infants bring up many ethical questions. Guidelines for intervention in the "periviable" period generally divide infants using predefined categories, such as "futile," "beneficial," and "gray zone" based on completed 7-day periods of gestation; however, such definitions often differ among countries. The ethical justification for using gestational age as the determination of the category boundaries is rarely discussed. Rational criteria used to make decisions regarding life-sustaining interventions must incorporate other important prognostic information. Precise guidelines based on imprecise data are not rational. Gestational age-based guidelines include an implicit judgment of what is deemed to be an unacceptably poor chance of "intact" survival but fail to explore the determination of acceptability. Furthermore, unclear definitions of severe disability, the difficulty, or impossibility, of accurately predicting outcome in the prenatal or immediate postnatal period make such simplistic formulae inappropriate. Similarly, if guidelines for intervention for the newborn are based on the "qualitative futility" of survival, it should be explicitly stated and justified according to established ethical guidelines. They should discuss whether newborn infants are morally different to older individuals or explain why thresholds recommended for intervention are different to recommendations for those in older persons. The aim should be to establish individualized goals of care with families while recognizing uncertainty, rather than acting on labels derived from gestational age categories alone.

Estimation of gestational age in early pregnancy from crown-rump length when gestational age range is truncated: the case study of the INTERGROWTH-21st Project

BACKGROUND

Fetal ultrasound scanning is considered vital for routine antenatal care with first trimester scans recommended for accurate estimation of gestational age (GA). A reliable estimate of gestational age is key information underpinning clinical care and allows estimation of expected date of delivery. Fetal crown-rump length (CRL) is recommended over last menstrual period for estimating GA when measured in early pregnancy i.e. 9+0-13+6 weeks.

METHODS

The INTERGROWTH-21st Project is the largest prospective study to collect data on CRL in geographically diverse populations and with a high level of quality control measures in place. We aim to develop a new gestational age estimation equation based on the crown-rump length (CRL) from women recruited between 9+0-13+6 weeks. The main statistical challenge is modelling data when the outcome variable (GA) is truncated at both ends, i.e. at 9 and 14 weeks.We explored three alternative statistical approaches to overcome the truncation of GA. To evaluate these strategies we generated a data set with no truncation of GA that was similar to the INTERGROWTH-21st Project CRL data, which we used to explore the performance of different methods of analysis of these data when we imposed truncation at 9 and 14 weeks of gestation. These 3 methods were first tested in a simulation based study using a previously published dating equation by Verburg et al. and evaluated how well each of them performed in relation to the model from which the data were generated. After evaluating the 3 approaches using simulated data based on the Verburg equations, the best approach will be applied to the INTERGROWTH-21st Project data to estimate GA from CRL.

RESULTS

Results of these rather "ad hoc" statistical methods correspond very closely to the "real data" for Verburg, a data set that is similar to the INTERGROWTH-21st project CRL data set.

CONCLUSIONS

We are confident that we can use these approaches to get reliable estimates based on INTERGROWTH-21st Project CRL data. These approaches may be a solution to other truncation problems involving similar data though their application to other settings would need to be evaluated.

Should a first trimester dating scan be routine for all pregnancies?

Accurate pregnancy dating is important for diagnostic and management decisions during pregnancy. Dating by last menstrual period is less reliable than dating by ultrasound, since the former has memory-related and other sources of inaccuracy. Dating by first trimester ultrasound, via the crown-rump length, has a 95% confidence range of ±5 days, slightly better than the ±8 days for dating by second trimester ultrasound at 14-20 weeks. This small difference appears to be too small to justify a routine first trimester scan for the purpose of dating the pregnancy.

Standardisation of crown-rump length measurement

Correct estimation of gestational age is essential for any study of ultrasound biometry and for everyday clinical practice. However, inconsistency in pregnancy dating may occur through differences in measurement methods or errors during measurement. In the INTERGROWTH-21(st) Project, pregnancies are dated by the last menstrual period, provided that it is certain and associated with a regular menstrual cycle, and the gestational age by dates concurs with a first-trimester ultrasound crown-rump length (CRL) estimation. Hence, there was a need to standardise CRL measurement methodology across the study sites in this international, multicentre project to avoid systematic differences in dating. To achieve uniformity we undertook the following steps: the ultrasound technique was standardised by disseminating an illustrated, operating manual describing CRL plane landmarks and calliper application, and posters describing the correct acquisition technique were disseminated for quick reference. To ensure that all ultrasonographers understood the methodology, they forwarded a log-book to the INTERGROWTH-21(st) Ultrasound Coordinating Unit, containing the answers to a written test on the manual material and five images of a correctly acquired CRL. Interpretation of CRL was also standardised by ensuring that the same CRL regression formula was used across all study sites. These methods should minimise potential systematic errors in dating associated with pooling data from different health institutions, and represent a model for standardising CRL measurement in future studies.

Effects of prematurity on the development of contrast sensitivity: testing the visual experience hypothesis

In order to investigate the effects of visual experience on early visual development, the current study compared contrast sensitivity across infants born with different degrees of moderate-to-late prematurity. Here the logic is that at any given postterm age, the most premature infants will have the oldest postnatal age. Given that postnatal age is a proxy for visual experience, the visual experience hypothesis predicts that infants who are more premature, yet healthy, should have higher sensitivity. Luminance (light/dark) and chromatic (red/green) contrast sensitivities (CS) were measured in 236 healthy infants (born -10 to +2 weeks relative to due date) between 5 and 32 weeks postterm age from due date and 8-38 weeks postnatal from birth date. For chromatic CS, we found clear evidence that infants who were most premature within our sample had the highest sensitivity. Specifically, 4-10 additional weeks of visual experience, by virtue of being born early, enhanced chromatic CS. For luminance CS, similar but weaker results were seen. Here, only infants with an additional 6-10 weeks of visual experience, and only at later age points in development, showed enhanced sensitivity. However, CS in preterm infants was still below that of fullterm infants with equivalent postnatal age. In sum, these results suggest that chromatic CS is influenced more by prematurity (and possibly visual experience) than luminance CS, which has implications for differential development of parvocellular and magnocellular pathways.

Day-specific probabilities of conception in fertile cycles resulting in spontaneous pregnancies

STUDY QUESTION

When, within the female cycle, does conception occur in spontaneously fertile cycles?

SUMMARY ANSWER

This study provides reference values of day-specific probabilities of date of conception in ongoing pregnancies. The maximum probability of being within a 5-day fertile window was reached on Day 12 following the last menstrual period (LMP).

WHAT IS KNOWN ALREADY

The true date of conception is not observable and may only be estimated. Accuracy of these estimates impacts on obstetric management of ongoing pregnancies. Timing of ovulation and fertility has been extensively studied in prospective studies of non-pregnant fertile women using error-prone proxies, such as hormonal changes, body-basal temperature and ultrasound, yielding day-specific probabilities of conception and fertile windows. In pregnant women, date of conception may be retrospectively estimated from early pregnancy fetal measurement by ultrasound.

STUDY DESIGN, SIZE, DURATION

Retrospective analysis of consecutive pregnancies in women referred for routine first-trimester screening, over a 3-year period (2009-2011) in a single ultrasound center (n = 6323).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Within the overall population, 5830 cases with a certain date of last menses were selected for analysis. The date of conception was estimated using a crown-rump length biometry and an equation derived from IVF/ICSI pregnancies. Day-specific probabilities of conception were estimated across several covariates, including age, cycle characteristics and ethnicity, using deconvolution methods to account for measurement error.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, the day-specific probability of conception sharply rises at 7 days after the LMP, reaching its maximum at 15 days and returning to zero by 25 days. Older women tend to conceive earlier within their cycle, as did women with regular cycles and white and black women compared with Asian ethnicity. The probability of being within the fertile window was 2% probability at Day 4, a maximum probability of 58% at Day 12 and a 5% probability by Day 21 of the cycle.

LIMITATIONS, REASONS FOR CAUTION

Although conception is believed to occur within hours following ovulation, a discrepancy is theoretically possible. However, when comparing our results to those of prospective studies, no such difference was found. The equation used for estimating the date of pregnancy was estimated in IVF/ICSI pregnancies, which could lead to potential bias in spontaneous pregnancies. However, in our population, the observed bias was negligible. Non-fertile cycles and early pregnancy losses are necessarily overlooked because of the nature of our data.

WIDER IMPLICATIONS OF THE FINDINGS

Because of the wider access to retrospective data and the potential bias in prospective studies of ovulation monitoring, this study should broaden the perspectives of future epidemiologic research in fertility and pregnancy monitoring.

STUDY FUNDING/COMPETING INTERESTS

None.

Ultrasound Reference Chart Based on IVF Dates to Estimate Gestational Age at 6-9 weeks' Gestation

Accurate determination of gestational age underpins good obstetric care. We assessed the performance of six existing ultrasound reference charts to determine gestational age in 1268 singleton IVF pregnancies, where “true” gestational age could be precisely calculated from date of fertilisation. All charts generated dates significantly different to IVF dates (P < 0.0001 all comparisons). Thus we generated a new reference chart, The Monash Chart, based on a line of best fit describing crown-rump length across 6 + 1 to 9 + 0 weeks of gestation (true gestational age) in the IVF singleton cohort. The Monash Chart, but none of the existing charts, accurately determined gestational age among an independent IVF twin cohort (185 twin pairs). When applied to 3052 naturally-conceived singletons scans, The Monash Chart generated estimated due dates that were different to all existing charts (P ≤ 0.004 all comparisons). We conclude that commonly used ultrasound reference charts have inaccuracies. We have generated a CRL reference chart based on true gestational age in an IVF cohort that can accurately determine gestational age at 6–9 weeks of gestation.

Density estimation of a biomedical variable subject to measurement error using an auxiliary set of replicate observations

Correcting for measurement error when estimating the density of a routinely collected biomedical variable is an important issue when describing reference values for both healthy and pathological states. The present work addresses the problem of estimating the density of a biomedical variable observed with measurement error without any a priori knowledge on the error density. Assuming the availability of a sample of replicate observations, either internal or external, which is generally easily obtained in clinical settings, we propose an estimator based on the non-parametric deconvolution theory with an adaptive procedure for cutoff selection, the replicates being used for an estimation of the error density. We illustrate this approach in two applicative examples: (i) the systolic blood pressure distribution density, using the Framingham Study data set, and (ii) the distribution of the timing of onset of pregnancy within the female cycle, using ultrasound measurements in the first trimester of pregnancy.