Evaluation of ultrasound-estimated date of delivery in 17,450 spontaneous singleton births: do we need to modify Naegele's rule?

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.

Leveraging External Validation Data: The Challenges of Transporting Measurement Error Parameters

Approaches to address measurement error frequently rely on validation data to estimate measurement error parameters (e.g., sensitivity and specificity). Acquisition of validation data can be costly, thus secondary use of existing data for validation is attractive. To use these external validation data, however, we may need to address systematic differences between these data and the main study sample. Here, we derive estimators of the risk and the risk difference that leverage external validation data to account for outcome misclassification. If misclassification is differential with respect to covariates that themselves are differentially distributed in the validation and study samples, the misclassification parameters are not immediately transportable. We introduce two ways to account for such covariates: (1) standardize by these covariates or (2) iteratively model the outcome. If conditioning on a covariate for transporting the misclassification parameters induces bias of the causal effect (e.g., M-bias), the former but not the latter approach is biased. We provide proof of identification, describe estimation using parametric models, and assess performance in simulations. We also illustrate implementation to estimate the risk of preterm birth and the effect of maternal HIV infection on preterm birth. Measurement error should not be ignored and it can be addressed using external validation data via transportability methods.

Ultrasonographic Estimation of the Gestational Age Using the Fetal Kidney Length in the Second and Third Trimesters of Pregnancy Among South Indian Antenatal Women: A Cross-Sectional Study

Background and Objective Accurately estimating the age of the fetus is crucial to prevent morbidity and mortality for both the fetus and mother during the perinatal period. Additionally, it enables early intervention in cases of complicated pregnancies. Multiple parameters are used for the estimation of fetal gestational age (FGA) and the expected date of delivery (EDD), but no single parameter is found to be accurate and standard. This study aims to analyze the fetal kidney length (FKL) as a means to estimate gestational age and investigate the growth pattern of the fetal kidney during the early and late weeks of gestation. Furthermore, it seeks to establish correlations between FKL and gold standard parameters from the 18th week to the 38th week of gestation. Methodology This cross-sectional research was carried out after obtaining proper institutional ethical clearance. The pregnant women who came to the gynecology outpatient department (OPD) between 18 and 38 weeks were included in this study after obtaining informed consent. The fetal biometry was measured using the ultrasonographic transducer (3-5 MHz). Results The mean FKL exhibited a consistent increase throughout the entire pregnancy, ranging from 16.50 ± 2.10 to 39.20 ± 3.10 mm. The rate of increase in FKL was significant between the early weeks (18-24) of pregnancy, with insignificant growth in other weeks of gestation. The growth of the fetal kidney (length) exhibited a gradual increase from the early weeks to the late weeks of pregnancy, with a consistent growth rate of approximately 1mm per week from 18 to 35 weeks. However, in the final three weeks of pregnancy (36th, 37th, and 38th weeks), the FKL measurements were recorded as 37.90 ± 3.90, 38.90 ± 3.10, and 40.20 ± 3.10 mm, respectively. A positive correlation was noted between the FKL with all standard parameters such as biparietal diameter (BPD), femur length (FL), head circumference (HC), and abdominal circumference (AC). Conclusions This study concluded that incorporating FKL alongside standard fetal biometric parameters such as BPD, FL, HC, and AC enhanced the accuracy of calculating FGA and EDD during the early second trimester. Furthermore, it proved beneficial in diagnosing fetal anomalies during early pregnancies.

Risk of ovarian cancer in women who give birth after assisted reproductive technology (ART)-a registry-based Nordic cohort study with follow-up from first pregnancy

BACKGROUND

There is concern that assisted reproductive technology (ART) may increase ovarian cancer risk, but previous studies are inconclusive. We compared ovarian cancer risk for women who gave birth after ART vs natural conception.

METHODS

Through linkage of nationwide registry data, we followed 3,303,880 initially nulliparous women in Denmark (1994-2014), Finland (1990-2014), Norway (1984-2015) and Sweden (1985-2015) from first pregnancy ≥22 weeks to ovarian cancer, emigration, death or end of follow-up (2014/2015). We estimated hazard ratios (HRs), adjusting for age, parity, maternal birth year and country, and for body mass index and smoking in subsamples.

RESULTS

Mean age at first birth was 27.7 years. During a mean follow-up of 14.4 person-years, 2683 participants (0.08%) developed ovarian cancer; 135 after ART and 2548 after natural conception only (incidence rates 11.6 and 5.5 per 100,000 person-years, respectively). The risk was higher for women who ever gave birth after ART (HR 1.70, 95% confidence interval 1.42-2.03) compared to natural conception. Associations were stronger for conventional in vitro fertilisation than for intracytoplasmic sperm injection.

CONCLUSIONS

Among parous women, ART-conception was associated with a higher risk of ovarian cancer than natural conception. Further studies should decipher whether this is causal or confounded by infertility or other factors.

Influence of different methods for calculating gestational age at birth on prematurity and small for gestational age proportions: a systematic review with meta-analysis

BACKGROUND

Recognizing premature newborns and small-for-gestational-age (SGA) is essential for providing care and supporting public policies. This systematic review aims to identify the influence of the last menstrual period (LMP) compared to ultrasonography (USG) before 24 weeks of gestation references on prematurity and SGA proportions at birth.

METHODS

Systematic review with meta-analysis followed the recommendations of the PRISMA Statement. PubMed, BVS, LILACS, Scopus-Elsevier, Embase-Elsevier, and Web-of-Science were searched (10-30-2022). The research question was: (P) newborns, (E) USG for estimating GA, (C) LMP for estimating GA, and (O) prematurity and SGA rates for both methods. Independent reviewers screened the articles and extracted the absolute number of preterm and SGA infants, reference standards, design, countries, and bias. Prematurity was birth before 37 weeks of gestation, and SGA was the birth weight below the p10 on the growth curve. The quality of the studies was assessed using the New-Castle-Ottawa Scale. The difference between proportions estimated the size effect in a meta-analysis of prevalence.

RESULTS

Among the 642 articles, 20 were included for data extraction and synthesis. The prematurity proportions ranged from 1.8 to 33.6% by USG and varied from 3.4 to 16.5% by the LMP. The pooled risk difference of prematurity proportions revealed an overestimation of the preterm birth of 2% in favor of LMP, with low certainty: 0.02 (95%CI: 0.01 to 0.03); I² 97%). Subgroup analysis of USG biometry (eight articles) showed homogeneity for a null risk difference between prematurity proportions when crown-rump length was the reference: 0.00 (95%CI: -0.001 to 0.000; I²: 0%); for biparietal diameter, risk difference was 0.00 (95%CI: -0.001 to 0.000; I²: 41%). Only one report showed the SGA proportions of 32% by the USG and 38% by the LMP.

CONCLUSIONS

LMP-based GA, compared to a USG reference, has little or no effect on prematurity proportions considering the high heterogeneity among studies. Few data (one study) remained unclear the influence of such references on SGA proportions. Results reinforced the importance of qualified GA to mitigate the impact on perinatal statistics.

TRIAL REGISTRATION

Registration number PROSPERO: CRD42020184646.

Estimated date of delivery with electronic medical records by a hybrid GBDT-GRU model

An accurate estimated date of delivery (EDD) helps pregnant women make adequate preparations before delivery and avoid the panic of parturition. EDD is normally derived from some formulates or estimated by doctors based on last menstruation period and ultrasound examinations. This study attempted to combine antenatal examinations and electronic medical records to develop a hybrid model based on Gradient Boosting Decision Tree and Gated Recurrent Unit (GBDT-GRU). Besides exploring the features that affect the EDD, GBDT-GRU model obtained the results by dynamic prediction of different stages. The mean square error (MSE) and coefficient of determination (R²) were used to compare the performance among the different prediction methods. In addition, we evaluated predictive performances of different prediction models by comparing the proportion of pregnant women under the error of different days. Experimental results showed that the performance indexes of hybrid GBDT-GRU model outperformed other prediction methods because it focuses on analyzing the time-series predictors of pregnancy. The results of this study are helpful for the development of guidelines for clinical delivery treatments, as it can assist clinicians in making correct decisions during obstetric examinations.

Changes in data management contribute to temporal variation in gestational duration distribution in the Swedish Medical Birth Registry

Multiple factors contribute to gestational duration variability. Understanding the sources of variability allows to design better association studies and assess public health measures. Here, we aimed to assess geographical and temporal changes in the determination of gestational duration and its reporting in Sweden between 1973 and 2012. Singleton live births between 1973 and 2012 were retrieved from the Swedish Medical Birth Register. Gestational duration trends in percentiles and rates of pre- and post-term deliveries were analyzed by plotting the values over time. Temporal changes in gestational duration based on ultrasound and last menstrual period (LMP) estimation methods were compared. Intervals between LMP date and LMP-based due date were analyzed to assess changes in expected gestational duration. In total, 3 940 577 pregnancies were included. From 1973 until 1985, the median of gestational duration estimated based on LMP or ultrasound decreased from 283 to 278 days, and remained stable until 2012. The distribution was relatively stable when ultrasound-based estimates were used. Until the mid-1990s, there was a higher incidence than expected of births occurring on every seventh gestational day from day 157 onward. On an average, these gestational durations were reported 1.8 times more often than adjacent durations. Until 1989, the most common expected gestational duration was 280 days, and thereafter, it was 279 days. The expected gestational duration varied from 279 to 281 days across different Swedish counties. During leap years, the expected gestational duration was one day longer. Consequently, leap years were also associated with significantly higher preterm and lower post-term delivery rates than non-leap years. Changes in data handling and obstetrical practices over the years contribute to gestational duration variation. The resulting increase in variability might reduce precision in association studies and hamper the assessment of public health measures aimed to improve pregnancy outcomes.

Naegele's rule and the length of pregnancy - A review

BACKGROUND

The proposition that a pregnancy is 40 weeks or 280 days in duration is attributed to the German obstetrician Franz Naegele (1778-1851). His rule adds nine months and seven days to the first day of the last menstrual period. The expected date of confinement from this formula is approximately right in the majority of cases. However, the idea that this rule can apply to every pregnant female - young or old, nulliparous or multigravida, Caucasian, Asian, African, or Indigenous - stretches credulity. In addition, many women regard the 40-week date as a deadline, which if crossed, may then place the baby under stress. Forty weeks is such a simple, round, convenient figure that it has proved difficult to challenge, despite criticism. Nonetheless, what might have been an appropriate formula in Germany in the 19th century deserves to be revisited in the 21st.

AIMS

To review the length of pregnancy, in the light of current technology, in particular ultrasound scanning, and assisted reproductive techniques.

MATERIAL AND METHODS

A Medline search was performed for variables on the length of pregnancy, the expected date of confinement, and prolonged pregnancy.

RESULTS

A number of factors were found to significantly influence the length of a pregnancy, including ethnicity, height, variations in the menstrual cycle, the timing of ovulation, parity and maternal weight.

CONCLUSIONS

Naegele's rule should be considered as a guideline for the expected date of confinement, and not a definite date.

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.

Importance of the environment for gestational duration variability and correlation between relatives - results from the Medical Swedish Birth Registry, 1973-2012

It has been suggested that the intergenerational associations in gestational age at delivery are considerably affected by temporal changes in the environmental conditions. We explored whether changing environment affects familial resemblance of gestational age at delivery. Understanding how correlation changes in different settings allows to design better studies aimed to detect genes and environmental factors involved in the parturition process. The Swedish Medical Birth Register was used to retrieve births during 1973–2012. In total, 454,433 parent-child, 2,247,062 full sibling, 405,116 maternal half-sibling and 469,995 paternal half-sibling pairs were identified. A decreasing trend in correlation, associated with increasing age gaps, was observed among all siblings, with the largest drop for full siblings, from ρ = 0.32 (95% confidence interval (CI): 0.31, 0.33) for full siblings with one-year gap to ρ = 0.16 (95% CI: 0.10, 0.22) for full siblings with age gap above 20 years. A variation in association between full siblings born up to two years apart was observed; estimate ρ = 0.28 (95% CI: 0.26, 0.3) in 1973, and ρ = 0.36 (95% CI: 0.33, 0.38) in 2012. Observed variability in the association in gestational age at delivery between the relatives with respect to their birth year or age gap suggests the existence of temporally changing environmental factors.

Toward point-of-care ultrasound estimation of fetal gestational age from the trans-cerebellar diameter using CNN-based ultrasound image analysis

Obstetric ultrasound is a fundamental ingredient of modern prenatal care with many applications including accurate dating of a pregnancy, identifying pregnancy-related complications, and diagnosis of fetal abnormalities. However, despite its many benefits, two factors currently prevent wide-scale uptake of this technology for point-of-care clinical decision-making in low- and middle-income country (LMIC) settings. First, there is a steep learning curve for scan proficiency, and second, there has been a lack of easy-to-use, affordable, and portable ultrasound devices. We introduce a framework toward addressing these barriers, enabled by recent advances in machine learning applied to medical imaging. The framework is designed to be realizable as a point-of-care ultrasound (POCUS) solution with an affordable wireless ultrasound probe, a smartphone or tablet, and automated machine-learning-based image processing. Specifically, we propose a machine-learning-based algorithm pipeline designed to automatically estimate the gestational age of a fetus from a short fetal ultrasound scan. We present proof-of-concept evaluation of accuracy of the key image analysis algorithms for automatic head transcerebellar plane detection, automatic transcerebellar diameter measurement, and estimation of gestational age on conventional ultrasound data simulating the POCUS task and discuss next steps toward translation via a first application on clinical ultrasound video from a low-cost ultrasound probe.

Estimated date of delivery based on second trimester fetal head circumference: A population-based validation of 21 451 deliveries

INTRODUCTION

Fetal biometry is used for determining gestational age and estimated date of delivery (EDD). However, the accuracy of the EDD depends on the assumed length of pregnancy included in the calculation. This study aimed at assessing the actual pregnancy length and accuracy of EDD prediction based on fetal head circumference measured at the second trimester.

MATERIAL AND METHODS

This was a population-based observational study with the following inclusion criteria: singleton pregnancy, head circumference dating in the second trimester, spontaneous onset or induction of delivery ≥ 294 days of gestation, live birth. The EDD was set anticipating a pregnancy length of 282 days. Bias in the prediction of EDD was defined as the difference between the actual date of birth and the EDD.

RESULTS

Head circumference measurements were available for 21 451 pregnancies. Ultrasound-dated pregnancies had a median pregnancy length of 283.03 days, corresponding to a method bias of 1.03 days (95% CI; 0.89-1.16). This bias was dependent on the head circumference at dating, ranging from -1.58 days (95% CI; -3.54 to 1.12) to 3.42 days (95% CI; 1.98-4.31). The median pregnancy length, based on the last menstrual period of women with a regular menstrual cycle (n = 12 985), was 283.15 days (95% CI; 282.91-283.31). A total of 5685 (22.9%, 95% CI; 22.4% to 23.4%) and 886 women (3.6%, 95% CI; 3.3%-3.8%) were still pregnant 7 and 14 days after the EDD, respectively.

CONCLUSIONS

Second trimester head circumference measurements can be safely used to predict EDD. A revision of the pregnancy length to 283 days will reduce the bias of EDD prediction to a level comparable with other methods.

MANAGEMENT OF ENDOCRINE DISEASE: Growth and growth hormone therapy in short children born preterm

Approximately 15 million babies are born preterm across the world every year, with less than 37 completed weeks of gestation. Survival rates increased during the last decades with the improvement of neonatal care. With premature birth, babies are deprived of the intense intrauterine growth phase, and postnatal growth failure might occur. Some children born prematurely will remain short at later ages and adult life. The risk of short stature increases if the child is also born small for gestational age. In this review, the effects of being born preterm on childhood growth and adult height and the hormonal abnormalities possibly associated with growth restriction are discussed, followed by a review of current information on growth hormone treatment for those who remain with short stature during infancy and childhood.

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.

Ultrasound-based gestational-age estimation in late pregnancy

OBJECTIVE

Accurate gestational-age (GA) estimation, preferably by ultrasound measurement of fetal crown-rump length before 14 weeks' gestation, is an important component of high-quality antenatal care. The objective of this study was to determine how GA can best be estimated by fetal ultrasound for women who present for the first time late in pregnancy with uncertain or unknown menstrual dates.

METHODS

INTERGROWTH-21^st was a large, prospective, multicenter, population-based project performed in eight geographically defined urban populations. One of its principal components, the Fetal Growth Longitudinal Study, aimed to develop international fetal growth standards. Each participant had their certain menstrual dates confirmed by first-trimester ultrasound examination. Fetal head circumference (HC), biparietal diameter (BPD), occipitofrontal diameter (OFD), abdominal circumference (AC) and femur length (FL) were measured every 5 weeks from 14 weeks' gestation until delivery. For each participant, a single, randomly selected ultrasound examination was used to explore all candidate biometric variables and permutations to build models to predict GA. Regression equations were ranked based upon minimization of the mean prediction error, goodness of fit and model complexity. An automated machine learning algorithm, the Genetic Algorithm, was adapted to evaluate > 64 000 potential polynomial equations as predictors.

RESULTS

Of the 4607 eligible women, 4321 (94%) had a pregnancy without major complications and delivered a live singleton without congenital malformations. After other exclusions (missing measurements in GA window and outliers), the final sample comprised 4229 women. Two skeletal measures, HC and FL, produced the best GA prediction, given by the equation log_e (GA) = 0.03243 × (log_e (HC))² + 0.001644 × FL × log_e (HC) + 3.813. When FL was not available, the best equation based on HC alone was log_e (GA) = 0.05970 × (log_e (HC))² + 0.000000006409 × (HC)³ + 3.3258. The estimated uncertainty of GA prediction (half width 95% interval) was 6-7 days at 14 weeks' gestation, 12-14 days at 26 weeks' gestation and > 14 days in the third trimester. The addition of FL to the HC model led to improved prediction intervals compared with using HC alone, but no further improvement in prediction was afforded by adding AC, BPD or OFD. Equations that included other measurements (BPD, OFD and AC) did not perform better.

CONCLUSIONS

Among women initiating antenatal care late in pregnancy, a single set of ultrasound measurements combining HC and FL in the second trimester can be used to estimate GA with reasonable accuracy. We recommend this tool for underserved populations but considerable efforts should be implemented to improve early initiation of antenatal care worldwide. © 2016 Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Temporal trends for pregnancy length in a hospital setting of Southern Spain

For centuries it has been considered that the due date for delivery in our species is 280 days after the onset of the last menstruation. However, in most cases this statement is not accurate. The main objective of this study was to determine the mean duration of pregnancy in our setting and whether it has experienced changes in recent years. A retrospective, population-based descriptive study was made of 102,169 deliveries assisted in Malaga University Hospital (Malaga, Andalusia, Spain) during the period 1998-2015. The mean gestational age at delivery was 269 days (SD 16 days), with a modal gestational age of 273 days. The mean duration of the singleton and multiple pregnancies was 271 days (SD 17 days) and 242 days (SD 20 days), respectively. A significant shortening of the duration of pregnancy was observed in the course of the study period.

An epigenetic clock for gestational age at birth based on blood methylation data

Background

Gestational age is often used as a proxy for developmental maturity by clinicians and researchers alike. DNA methylation has previously been shown to be associated with age and has been used to accurately estimate chronological age in children and adults. In the current study, we examine whether DNA methylation in cord blood can be used to estimate gestational age at birth.

Results

We find that gestational age can be accurately estimated from DNA methylation of neonatal cord blood and blood spot samples. We calculate a DNA methylation gestational age using 148 CpG sites selected through elastic net regression in six training datasets. We evaluate predictive accuracy in nine testing datasets and find that the accuracy of the DNA methylation gestational age is consistent with that of gestational age estimates based on established methods, such as ultrasound. We also find that an increased DNA methylation gestational age relative to clinical gestational age is associated with birthweight independent of gestational age, sex, and ancestry.

Conclusions

DNA methylation can be used to accurately estimate gestational age at or near birth and may provide additional information relevant to developmental stage. Further studies of this predictor are warranted to determine its utility in clinical settings and for research purposes. When clinical estimates are available this measure may increase accuracy in the testing of hypotheses related to developmental age and other early life circumstances.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-016-1068-z) contains supplementary material, which is available to authorized users.

Dating of Pregnancy in First versus Second Trimester in Relation to Post-Term Birth Rate: A Cohort Study

Objectives

To evaluate in a national standardised setting whether the performance of ultrasound dating during the first rather than the second trimester of pregnancy had consequences regarding the definition of pre- and post-term birth rates.

Methods

A cohort study of 8,551 singleton pregnancies with spontaneous delivery was performed from 2006 to 2012 at Copenhagen University Hospital, Holbæk, Denmark. We determined the duration of pregnancy calculated by last menstrual period, crown rump length (CRL), biparietal diameter (1^st trimester), BPD (2^nd trimester), and head circumference and compared mean and median durations, the mean differences, the systematic discrepancies, and the percentages of pre-term and post-term pregnancies in relation to each method. The primary outcomes were post-term and pre-term birth rates defined by different dating methods.

Results

The change from use of second to first trimester measurements for dating was associated with a significant increase in the rate of post-term deliveries from 2.1–2.9% and a significant decrease in the rate of pre-term deliveries from 5.4–4.6% caused by systematic discrepancies. Thereby 25.1% would pass 41 weeks when GA is defined by CRL and 17.3% when BPD (2^nd trimester) is used. Calibration for these discrepancies resulted in a lower post-term birth rate, from 3.1–1.4%, when first compared to second trimester dating was used.

Conclusions

Systematic discrepancies were identified when biometric formulas were used to determine duration of pregnancy. This should be corrected in clinical practice to avoid an overestimation of post-term birth and unnecessary inductions when first trimester formulas are used.

Trends in All-Cause Mortality across Gestational Age in Days for Children Born at Term

Background

Term birth is a gestational age from 259 days to 293 days. However trends in mortality according to gestational ages in days have not yet been described in this time period.

Methods and Findings

Based on nation-wide registries, we conducted a population-based cohort study among all children born at term in Denmark from 1997 to 2004 to estimate differences in mortality across gestational ages in days among singletons born at term. We studied early-neonatal mortality, neonatal mortality, infant mortality, and five-year mortality. Children were followed from birth up to the last day of the defined mortality period or December 31, 2009. A total of 360,375 singletons born between 259 and 293 days of gestation were included in the study. Mortality decreased with increasing gestational age in days and the highest mortality was observed among children born at 37 week of gestation. A similar pattern was observed when analyses were restricted to children born to by mothers without pregnancy complications.

Conclusions

This study demonstrates heterogeneity in mortality rates even among singletons born at term. The highest mortality was observed among children born 37 weeks of gestation, which call for cautions when inducing labor in term pregnancies just reaching 37 weeks of gestation. The findings support that 37 weeks of gestation should be defined as early term.

A standardized template for clinical studies in preterm birth

BACKGROUND

Preterm birth is a major societal and economic problem accounting for 80 to 90% of neonatal morbidity and mortality worldwide. It is recognized as a complex multifactorial condition comprising several distinct clinical phenotypes with different underlying etiologies. As animal models are expensive and fail to mimic the biology of spontaneous preterm birth in humans, understanding the pathophysiology requires detailed clinical studies. Meta-analyses and clinical translation of data, however, are limited by heterogeneity of study design and size, publication and reporting biases, definition of patient groups, and a lack of standard universal definitions. This article provides a harmonized open-source template for designing clinical studies addressing preterm birth.

METHODS

Recommendations are made for clinical definitions, choice and assignment to preterm birth phenotypes, selection of enriched populations and control pregnancies, and potential confounding factors. In addition, recommendations are made for study design, sample size and power calculations, the minimal data sets needed for any study of preterm birth, and the optimal data set of an ideal study.

RESULTS

Recommended patient phenotypes are infection, uterine overdistension, hemorrhage, stress (either maternal or fetal), and idiopathic. Confounding factors include medical conditions, obesity, antenatal glucocorticoids, multifetal pregnancies, and fetal sex. Guidelines regarding study design, sample size, and clinical data acquisition are provided to serve as a universal template for preterm birth studies.

CONCLUSIONS

Adoption of a harmonized template will allow generation of protocols and studies with a basic degree of compatibility and will allow data to be compared, and samples and data sets to be combined for meaningful meta-analyses.

A new population-based term prediction model vs. two traditional sample-based models: validation on 9046 ultrasound examinations

OBJECTIVES

To compare results of predictions of date of delivery from a new population-based model with those from two traditional regression models.

METHODS

We included 9046 fetal biparietal diameter (BPD) measurements and 8776 femur length (FL) measurements from the routine ultrasound examinations at Stavanger University Hospital between 2001 and 2007. The prediction models to be validated were applied to the data, and the resulting predictions were compared with the actual time of the subsequent deliveries. The primary measure was the median bias (the difference between the true and the predicted date of delivery), calculated for each method, for the study population as a whole and for three subgroups of BPD/FL measurements. We also assessed the proportion of births within ± 14 days of the predicted day, and rates of preterm and post-term deliveries, which were regarded as secondary measures.

RESULTS

For the population-based model, the median bias was -0.15 days (95% confidence interval (CI), -0.43 to 0.12) for the BPD-based, and -0.48 days (95% CI, -0.86 to -0.46) for the FL-based predictions, and both biases were stable over the inclusion ranges. The biases of the traditional regression models varied, depending on the fetal size at the time of the examination; the extremes were -3.2 and + 4.5 days for the BPD-based, and -1.0 and + 5.0 days for the FL-based predictions.

CONCLUSIONS

The overall biases, as well as the biases for the subgroups, were all smaller with the population-based model than with the traditional regression models, which exhibited substantial biases in some BPD and FL subcategories. For the population-based model, the FL-based predictions were in accordance with the BPD-based predictions.

Fetal age assessment based on 2nd trimester ultrasound in Africa and the effect of ethnicity

BACKGROUND

The African population is composed of a variety of ethnic groups, which differ considerably from each other. Some studies suggest that ethnic variation may influence dating. The aim of the present study was to establish reference values for fetal age assessment in Cameroon using two different ethnic groups (Fulani and Kirdi).

METHODS

This was a prospective cross sectional study of 200 healthy pregnant women from Cameroon. The participants had regular menstrual periods and singleton uncomplicated pregnancies, and were recruited after informed consent. The head circumference (HC), outer-outer biparietal diameter (BPDoo), outer-inner biparietal diameter and femur length (FL), also called femur diaphysis length, were measured using ultrasound at 12-22 weeks of gestation. Differences in demographic factors and fetal biometry between ethnic groups were assessed by t- and Chi-square tests.

RESULTS

Compared with Fulani women (N = 96), the Kirdi (N = 104) were 2 years older (p = 0.005), 3 cm taller (p = 0.001), 6 kg heavier (p < 0.0001), had a higher body mass index (BMI) (p = 0.001), but were not different with regard to parity. Ethnicity had no effect on BPDoo (p = 0.82), HC (p = 0.89) or FL (p = 00.24). Weight, height, maternal age and BMI had no effect on HC, BPDoo and FL (p = 0.2-0.58, 0.1-0.83, and 0.17-0.6, respectively). When comparing with relevant European charts based on similar design and statistics, we found overlapping 95% CI for BPD (Norway & UK) and a 0-4 day difference for FL and HC.

CONCLUSION

Significant ethnic differences between mothers were not reflected in fetal biometry at second trimester. The results support the recommendation that ultrasound in practical health care can be used to assess gestational age in various populations with little risk of error due to ethnic variation.

A retrospective fetal ultrasound study of brain size in autism

BACKGROUND

Despite evidence of possible abnormalities during fetal development, no study to date has attempted to investigate fetal brain growth in autism. Fetal head circumference (HC) and biparietal diameter (BPD) are highly correlated with fetal brain volume and are measured on fetal ultrasounds.

METHODS

We used retrospective fetal ultrasound data to examine fetal head and body size during midgestation in children later diagnosed with autism. Second trimester fetal ultrasounds were collected for 45 autistic subjects and 222 control subjects. The HC, BPD, abdominal circumference (AC), and femur length (FL) measurements were extracted from the ultrasound records and standardized. The standardized growth parameters and discrepancies between them were compared in autism and control subjects.

RESULTS

The autism group did not differ significantly from control subjects on individual measures of standardized HC, BPD, AC, and FL. Fetal HC was normal in the autism group. Preliminary findings suggest a tendency for fetal BPD to be large relative to HC in the autism group. An index of fetal body size, AC was significantly decreased in multiplex compared with simplex autism, and HC showed a trend decrease. The rate of pyelectasis was increased and breech position decreased in the autism group. No lateral ventricle abnormalities were reported.

CONCLUSIONS

This preliminary study suggests that fetal head circumference is not abnormal in autism. The preliminary findings identify a subtle disturbance in uniformity of fetal brain growth and in renal development in some autistic cases, and differences in fetal development between simplex and multiplex autism.

A direct method for ultrasound prediction of day of delivery: a new, population-based approach

OBJECTIVES

To introduce a direct population-based method for prediction of term based on ultrasound measurements of the biparietal diameter and femur length in the second trimester of pregnancy.

METHODS

Our data consisted of 41 343 ultrasound scans from a non-selected population, prospectively collected during the years 1987-2004. Using measurements of biparietal diameter and femur length, we constructed prediction curves for term by computing median remaining time of pregnancy from the ultrasound measurement to birth. A local linear quantile regression method was used to smooth the median and quantile curves.

RESULTS

The quality of term prediction was stable over the prediction range for both biparietal diameter (25-60 mm) and femur length (11-42 mm). The femur-based predictions were nearly as good as those of the biparietal diameter. For the biparietal diameter, the median of the prediction residual was -0.09 days; 87.2% of the births fell within +/- 14 days of the predicted day of delivery, 3.5% births were classified as preterm and 4.3% as post-term. The corresponding figures for femur length were - 0.04 days, 86.7%, 3.6% and 4.5%. The covariates maternal age, parity, mother's smoking habits, sex of the fetus and examination year generally affected the predicted term by less than 1 day.

CONCLUSIONS

This direct ultrasound-based prediction of term using population-based data avoids selection biases possibly present in smaller prospective samples. The model obviates the dependence on last menstrual period found in standard methods for term prediction, and allows an immediate assessment of prediction quality in a population setting. The femur-based predictions had a quality similar to those based on the biparietal diameter. The model can be updated continuously as new data are collected.

Induction of Labor or Serial Antenatal Fetal Monitoring in Postterm Pregnancy

OBJECTIVE

To compare induction of labor at gestational age 41 weeks with expectant management in regard to neonatal morbidity. Secondary aims were to assess the effect of these managements on mode of delivery and maternal complications.

METHODS

Between September 2002 and July 2004, postterm women with singleton cephalic presentation and no prelabor rupture of membranes were randomly assigned to induction of labor at 289 days or antenatal fetal surveillance every third day until spontaneous labor. Main outcome measures were neonatal morbidity, operative delivery rates, and maternal complications.

RESULTS

Five hundred eight women were randomly assigned, 254 in each group. No differences of clinical importance were observed in women in whom labor was induced compared with women who were expectantly managed with regard to the following outcomes: neonates whose 5-minute Apgar score was less than 7 (three neonates in the induction group compared with four in the monitoring group, P=.72); neonates whose umbilical cord pH was less than 7 (three compared with two, P=.69); prevalence of cesarean delivery (28 compared with 33, P=.50); or prevalence of operative vaginal delivery (32 compared with 27, P=.49). In the induction group more women had precipitate labors (33 compared with 12, P<.01; number needed to treat was 13), and the duration of second stage of labor was more often less than 15 minutes (94 compared with 56, P<.01; number needed to treat was 7).

CONCLUSION

No differences were found between the induced and monitored groups regarding neonatal morbidity or mode of delivery, and the outcomes were generally good.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT00385229.

LEVEL OF EVIDENCE

I.

Accuracy of second trimester fetal head circumference and biparietal diameter for predicting the time of spontaneous birth

AIMS

Previous studies suggested that head circumference (HC) predicts the date of confinement better than the biparietal diameter (BPD). The present study aimed to prospectively test this assumption.

METHODS

A prospective study including 4179 consecutive women attending the second trimester routine ultrasound examination at 17-20 weeks of gestation. Outer-outer BPD and HC were determined as the average of three repeated measurements. Twins were excluded. Time of delivery was noted, the differences between this and the predicted date of delivery calculated with HC and BPD (based on a pregnancy duration of 282 days), and the two methods were compared using Wilcoxon signed rank test.

RESULTS

For the entire group, the median differences between actual and predicted delivery with HC and BPD were 0.9 and 1.2 days, respectively. For deliveries with a spontaneous onset of labor (n=3336) the corresponding differences were 0.9 and 1.4 days. The difference between the HC and BPD methods was significant (P<0.0001). In the group of spontaneous onset of labor, there were 05.6% post-term pregnancies (>or=296 days) according to HC and 5.7% according to BPD.

CONCLUSION

Provided that the expected pregnancy duration was 282 days, both HC and BPD predicted spontaneous birth with a mean accuracy of one day, HC being significantly better than BPD.

Prediction of delivery date by sonography in the first and second trimesters

OBJECTIVE

To compare the dates of delivery predicted by last menstrual period (LMP), crown-rump length (CRL) and biparietal diameter (BPD) with the actual date of delivery in a population of pregnant women divided into those with certain and those with uncertain LMP.

METHODS

Healthy women were enrolled at the first visit during their pregnancy to a general practitioner in Odense, Denmark, and underwent ultrasound examinations in the first and second trimesters. Data from a study of 798 women who gave birth in the period August 2001 to April 2003 are presented, although only the 657 spontaneous deliveries were used for analysis (n = 339 and 318 in the certain and uncertain LMP groups, respectively). Data on pregnancy and delivery were collected from the medical records. Wilcoxon's signed rank test was used to test the hypothesis of no difference in prediction error (predicted - actual date of delivery) between the three methods.

RESULTS

The median prediction errors estimated by sonography in the first and second trimesters and by corrected LMP according to cycle length were 2.32, 0.16, and 3.00 days, respectively, in women with certain LMP, and 1.71, 0.00, and 3.00 days, respectively, in women with uncertain LMP. The median gestational age at delivery estimated by sonography in the first and second trimesters and by corrected LMP according to cycle length was 282, 280, and 283 days, respectively, in both groups.

CONCLUSION

An ultrasound examination in the second trimester (17-22 completed weeks) is the best predictor of the date of delivery at the individual level, followed by an ultrasound examination in the first trimester. Having an uncertain LMP does not affect the sonographic prediction of date of delivery.

Changes in the gestational age distribution among U.S. singleton births: impact on rates of late preterm birth, 1992 to 2002

There is mounting evidence that infants born late preterm (34-36 weeks) are at greater risk for morbidity than term infants. This article examines the changing epidemiology of gestational length among singleton births in the United States, from 1992 to 2002. Analyzing gestational age by mode of delivery, the distribution of spontaneous births shifted to the left, with 39 weeks becoming the most common length of gestation in 2002, compared with 40 weeks in 1992 (P < 0.001). Deliveries at > or =40 weeks gestation markedly decreased, accompanied by an increase in those at 34 to 39 weeks (P < 0.001). Singleton births with PROM or medical interventions had similar trends. Changes in the distribution of all singleton births differed by race/ethnicity, with non-Hispanic white infants having the largest increase in late preterm births. These observations, in addition to emerging evidence of increased morbidity, suggest the need for investigation of optimal obstetric and neonatal management of these late preterm infants.

Correlation between self-reported gestational age and ultrasound measurements

BACKGROUND

We studied the agreement between different measurements of gestational age, i.e. self-reported gestational age in the Danish National Birth Cohort Study, ultrasound-estimated gestational age from the medical records in one Danish county and gestational age from the Danish National Hospital Discharge Register.

METHODS

The ultrasound-estimated gestational length was based on the size of the biparietal diameter. The ultrasound-estimated gestational length was related to corrected and uncorrected last menstrual period estimates in the Danish National Cohort Study, and to the gestational length recorded in the Danish National Discharge Register. Non-parametric statistics were used in the analysis.

RESULTS

The gestational ages estimated by ultrasound were 2-3 days shorter than gestational ages estimated by the other methods. The gestational ages recorded by the Discharge Register and the gestational ages based on corrected last menstrual period did not differ significantly.

CONCLUSION

The self-reported gestational age in The Danish National Birth Cohort is in good concordance both with data from the National Hospital Discharge Register and with ultrasound-estimated gestational age.

Fetal age assessment based on ultrasound head biometry and the effect of maternal and fetal factors

BACKGROUND

Maternal height and weight have increased during the past 20 years, as has birthweight. The aim of the present study was to establish new reference charts for gestational age (GA) assessment using fetal biparietal diameter (BPD) and head circumference (HC), and to determine the effect of maternal and fetal factors on age assessment.

METHODS

This was a prospective, cross-sectional study of 650 healthy women with regular menstrual periods and singleton uncomplicated pregnancies, recruited after written consent. BPD (outer-outer) and HC were measured at 10-24 weeks of gestation. We used regression analysis to construct mean curves and assess the effect of maternal and fetal factors on age assessment.

RESULTS

BPD and HC were successfully measured in 642 participants. Using BPD and HC before 20 weeks, the new charts gave 3-8 days higher GA assessment than the charts presently in use, and <1 day difference compared to other recently established charts. Maternal age, multiparity, fetal gender, breech position and shape of fetal head affect GA estimation by 1-2 days when using BPD (p = 0.0001-0.02). Only maternal age and fetal gender affected GA estimation when using HC (</= 1 day, p = 0.001).

CONCLUSIONS

Our new charts for assessing gestational age based on fetal head biometry are notably different from charts presently in use. Maternal and especially fetal factors affect gestational age assessment when using BPD, but less so for the HC method, which is suggested as the more robust method.

Circle of time: errors in the use of the pregnancy wheel

OBJECTIVE

Despite the accuracy of pregnancy dating by ultrasound, obstetricians commonly use the pregnancy wheel for the assessment of gestational age at each visit. However, there has been limited assessment of the accuracy of the wheel, or variation among wheels. This study sought to determine the accuracy of pregnancy wheels in predicting term gestation, when entering first-trimester ultrasound-determined dating.

METHODS

A selection of four pregnancy wheels of varying types were utilized to determine estimated date of delivery (EDD) based upon an ultrasound assessment of 12 0/7 weeks' gestation at random dates throughout each of the 12 months of the year. As a control, EDD was calculated as 196 days from the 12 0/7 week ultrasound assessment by a computerized program using the years 2003-04. The mean difference in days between each wheel and the computer-assessed EDD was determined. Statistical comparison was performed with Kruskal-Wallis one-way analysis of variance with post-hoc Dunnett's test.

RESULTS

There were marked differences between the EDD determined by wheels versus the computer. One wheel differed by an average of more than 3 days from computer-assessed EDD, with a range of + 1 to +5 days. The difference between wheels and computer-assessed EDD varied monthly.

CONCLUSION

In view of the need for accurate gestational age assessment for clinical interventions (e.g. post-dates testing) clinicians should be aware of the potential inaccuracies of pregnancy wheels.

Perinatal and maternal complications related to postterm delivery: a national register-based study, 1978-1993

OBJECTIVE

This study was undertaken to estimate the risk of fetal and maternal complications associated with postterm delivery in Denmark.

STUDY DESIGN

A cross-sectional study that used records from the Danish Medical Birth Registry from 1978 to 1993 was performed. All women with registered prolonged pregnancy (n = 78022) and a 5% random sample of all women who gave birth (n = 47021) were linked to the Danish National Discharge Register. We established a postterm group of 77956 singleton deliveries and a term group of 34140 singleton spontaneous deliveries. Logistic regression models were used to analyze data.

RESULTS

The risk of perinatal and obstetric complications was high in postterm delivery compared with term delivery (adjusted odds ratios between 1.2 and 3.1). The risk of perinatal death was 1.33 (1.05-1.68).

CONCLUSION

Postterm delivery was associated with significantly increased risks of perinatal and maternal complications in Denmark in the period from 1978 to 1993.

How does early ultrasound scan estimation of gestational age lead to higher rates of preterm birth?

OBJECTIVE

Early ultrasound scanning estimation of gestational age is known to increase the reported preterm delivery rate (<37 completed weeks) compared with estimation by date of the last normal menstrual period, but it is unclear how this systematic difference arises.

STUDY DESIGN

This study was a hospital-based study of 44,623 women who delivered a live-born or stillborn infant between January 1, 1978, and March 31, 1996, and who had both last normal menstrual period-based and early (usually at 16-18 weeks) ultrasound scan-based gestational age estimates. Cross-classification of the 2 estimates by completed weeks was used to examine the direction and magnitude of the differences between them and to compare the resulting classifications of preterm birth.

RESULTS

The early ultrasound scan-based gestational age distribution was shifted uniformly to the left (ie, lower gestational age) relative to the last normal menstrual period gestational age distribution; the early ultrasound scan-based preterm delivery rate was 9.1%, which was 19.5% (n = 659 births) higher than the 7.6% rate by last normal menstrual period (P <.0001). The last normal menstrual period estimate exceeded the early ultrasound scan estimate far more often than the reverse, up to and including early ultrasound scan estimates of 40 weeks. No concentration of 4-week discrepancies was observed in either direction, as would be expected with random or systematic errors in recall of the last normal menstrual period. The absolute number of births at 37 to 39 weeks of gestation (by last normal menstrual period) that were reclassified as preterm (n = 1206 births) was much higher than the number of preterm births at 34 to 36 weeks of gestation that were reclassified as term (n = 581 births). The net increase of 625 preterm births (from 581 to 1206 births) that resulted from reclassification of births at 37 to 39 last normal menstrual period weeks accounted for 95% of the total 659-birth increase in early ultrasound scan-based preterm births at all last normal menstrual period gestational ages.

CONCLUSION

Early ultrasound scanning reduces the gestational age estimate across the entire gestational age range; early ultrasound scan-based reclassification of gestational age results in a substantial increase in the prevalence of preterm births. Small downward reclassifications exceed upward reclassifications of similar magnitude, which is consistent with previous reports that delayed (>14 days) ovulation is more frequent than early (<14 days) ovulation.

Birth characteristics and subsequent risk for breast cancer in very young women

There is growing evidence that prenatal exposures may influence later breast cancer risk. This matched case-control study used linked New York State birth and tumor registry data to examine the association between birth characteristics and breast cancer risk among women aged 14-37 years. Cases were women diagnosed with breast cancer between 1978 and 1995 who were also born in New York after 1957 (n = 484). For each case, selected controls were the next six liveborn females with the same maternal county of residence. The authors found a J-shaped association between birth weight and breast cancer risk, and very high birth weight (> or =4,500 g) was associated with the greatest elevation in risk (adjusted odds ratio (OR) = 3.10, 95% confidence interval (CI): 1.18, 7.97). The association of maternal age with breast cancer risk was also J-shaped, with maternal age of more than 24 years showing a positive, linear association (adjusted OR = 1.94, 95% CI: 1.18, 3.18 for maternal age > or =35 vs. 20-24 years; p for trend = 0.02). In contrast, women born very preterm had a lower risk (adjusted OR = 0.11, 95% CI: 0.02, 0.79 for gestational age <33 vs. > or =37 weeks). These findings support a role for early life factors in the development of breast cancer in very young women.

A discrepancy between gestational age estimated by last menstrual period and biparietal diameter may indicate an increased risk of fetal death and adverse pregnancy outcome

OBJECTIVE

To determine if the discrepancy between gestational age estimated by last menstrual period and by biparietal diameter (GALMP - GABPD) is associated with adverse pregnancy outcome.

DESIGN

Population-based follow up study.

POPULATION

Singleton pregnancies were studied when a reliable date of last menstrual period and biparietal diameter measured between 12 and 22 weeks of gestation was available (n = 16,469).

METHODS

Logistic regression analysis and Kaplan-Meier survival analysis were used to analyse the association between GALMP - GABPD and adverse pregnancy outcome.

MAIN OUTCOME MEASURES

Adverse outcome was defined as abortion after 12 weeks of gestation, still-birth or postnatal death within one year of birth, delivery < 37 weeks of gestation, a birthweight < 2,500 g or a sex-specific birthweight lower than 22% below the expected.

RESULTS

The risk of death was more than doubled if GALMP - GABPD of > or = 8 days was compared with GALMP - GABPD of < 8 days (OR 2.2; 95% CI 1.6-3.1). The risk of death was a factor of 6.1 higher if GALMP - GABPD of > or = 8 days was combined with increased (> 2 x multiple of median) maternal alpha-fetoprotein measured in the 2nd trimester.

CONCLUSIONS

A discrepancy between GALMP and GABPD generally reflects the precision of the two methods used to predict term pregnancy. However, a positive discrepancy of more than seven days, particularly with high maternal alpha-fetoprotein, might indicate intrauterine growth retardation and an increased risk of adverse perinatal outcome.