Errors in gestational age: evidence of bleeding early in pregnancy

Variation in Fetal Weight Percentile Estimates

OBJECTIVES

Weight percentiles are generally reported without any indication of error. This variation can lead a fetus being mistakenly classified erroneously as having intrauterine growth restriction (IUGR) or macrosomia. The goal of this study was to compare estimated weight percentiles with the actual observed weight percentile for each gestational age in a large cohort of fetuses being scanned in our institution.

METHODS

After IRB approval the radiology information system data base was retrospectively searched for all obstetrical US reports obtained during the late second and third trimesters from July 1, 2014, until July 1, 2020. Demographic information, fetal weight, and weight percentile information were obtained from these reports. Quantile-quantile plots were created for all gestational ages and all ethnicities.

RESULTS

Our study included 6259 ultrasounds in 4060 patients. Mean maternal age of the total group was 31.68 years (ranging 15-53 years). When all subjects were considered, the median values in our QQ plots approximated the line of identity. However, there was considerable variation for a given estimate, implying that estimated fetal weight percentiles are only very rough predictors of the actual percentile.

CONCLUSION

Estimated fetal weight percentiles are only very rough predictors of the actual percentile. We therefore suggest that estimates of the weight percentile should be reported along with an estimate of the expected variation. Recognition of variations in weight percentile should be considered in the greater clinical context, and could potentially prevent misdiagnosis of growth restriction and macrosomia as well as the subsequent overutilization of resources, unnecessary interventions, and maternal stress.

Temporal trends and risk of small for gestational age (SGA) infants among Asian American mothers by ethnicity

PURPOSE

To examine the temporal trends and risk of small for gestational age (SGA) phenotypes across Asian American ethnic groups.

METHODS

We conducted a population-based retrospective study using the 1992-2018 natality data files obtained from the National Vital Statistics System. Joinpoint regression modeling was employed to calculate the average annual percentage change in SGA birth rates among Asian American sub-groups and NH-White women. Logistic regression was utilized to compute the adjusted odds ratio and 95% confidence interval for the association between maternal race (Asian American sub-groups vs. NH-White) and SGA birth and its phenotypes.

RESULTS

We analyzed data on 2,821,798 Asian Americans and 62,174,875 NH-White US live-born infants. Overall, NH-Whites had the lowest SGA rates, while all the Asian ethnic groups had almost consistently higher rates during the 27-year period. Disparity in SGA births in the Asian subgroups was observed. Compared to NH-Whites, stratified analyses showed varying and significantly higher odds of any SGA in all Asian ethnic groups. Asian Indians had the highest odds [adjusted odds ratio (AOR) = 2.23, 95% confidence interval (CI) = 2.22-2.23] of any SGA compared to NH-Whites.

CONCLUSIONS

Our findings support the evidence that Asian Americans are not a homogenous group and highlight the need to disentangle these differences when conducting population health research and interventions among Asian Americans.

Reliability of last menstrual period recall, an early ultrasound and a Smartphone App in predicting date of delivery and classification of preterm and post-term births

Background

A reliable expected date of delivery (EDD) is important for pregnant women in planning for a safe delivery and critical for management of obstetric emergencies. We compared the accuracy of LMP recall, an early ultrasound (EUS) and a Smartphone App in predicting the EDD in South African pregnant women. We further evaluated the rates of preterm and post-term births based on using the different measures.

Methods

This is a retrospective sub-study of pregnant women enrolled in a randomized controlled trial between October 2017-December 2019. EDD and gestational age (GA) at delivery were calculated from EUS, LMP and Smartphone App. Data were analysed using SPSS version 25. A Bland–Altman plot was constructed to determine the limits of agreement between LMP and EUS.

Results

Three hundred twenty-five pregnant women who delivered at term (≥ 37 weeks by EUS) and without pregnancy complications were included in this analysis. Women had an EUS at a mean GA of 16 weeks and 3 days). The mean difference between LMP dating and EUS is 0.8 days with the limits of agreement 31.4–30.3 days (Concordance Correlation Co-efficient 0.835; 95%CI 0.802, 0.867). The mean(SD) of the marginal time distribution of the two methods differ significantly (p = 0.00187). EDDs were < 14 days of the actual date of delivery (ADD) for 287 (88.3%;95%CI 84.4–91.4), 279 (85.9%;95%CI 81.6–89.2) and 215 (66.2%;95%CI 60.9–71.1) women for EUS, Smartphone App and LMP respectively but overall agreement between EUS and LMP was only 46.5% using a five category scale for EDD-ADD with a kappa of .22. EUS 14–24 weeks and EUS < 14 weeks predicted EDDs < 14 days of ADD in 88.1% and 79.3% of women respectively. The proportion of births classified as preterm (< 37 weeks) was 9.9% (95%CI 7.1–13.6) by LMP and 0.3% (95%CI 0.1–1.7) by Smartphone App. The proportion of post-term (> 42 weeks gestation) births was 11.4% (95%CI 8.4–15.3), 1.9% (95%CI 0.9–3.9) and 3.4% (95%CI 1.9–5.9) by LMP, EUS and Smartphone respectively.

Conclusions

EUS and Smartphone App were the most accurate to estimate the EDD in pregnant women. LMP-based dating resulted in misclassification of a significantly greater number of preterm and post-term deliveries compared to EUS and the Smartphone App.

An updated reference for age-sex-specific birth weight percentiles stratified for ethnicity based on data from all live birth infants between 2005 and 2014 in Alberta, Canada

OBJECTIVE

This study aims to update the current reference for sex-specific birth weight percentiles by gestational age, overall and for specific ethnic groups, based on data from all singleton live-birth deliveries from 2005 to 2014 in Alberta, Canada.

METHODS

Infant and maternal information were captured in the Alberta Vital Statistics-Births Database for 473,115 singleton infants born to 311,800 women between January 1, 2005 and December 31, 2014. Within each sex, and each sex-ethnic group, birth weights were modelled by gestational age using generalized additive models and natural cubic splines. Crude and corrected estimates for birth weight percentiles including cut-off values for large for gestational age (LGA) and small for gestational age (SGA) were calculated by sex and sex-ethnic group, and gestational age for singleton live births.

RESULTS

LGA and SGA cut-offs were lower for females than for males for all gestational ages. The SGA and LGA percentiles were greater for both male and female very preterm infants in Alberta compared to previous national references. Ethnicity-specific LGA and SGA cut-offs for term Chinese and preterm and at-term South Asian infants were consistently lower than those for both the general population in Alberta and the previous national reference. South Asian infants had lower birth weights at almost all gestational ages compared with the other groups.

CONCLUSION

The updated birth weight percentiles presented in this study highlight the differences in SGA and LGA cut-offs among infants from South Asian, Chinese, and the general population, which may be important for clinical perinatal care.

Clinical Evaluations Have Low Sensitivity for Identifying Preterm Infants in a Clinical Trial in a Limited Resource Setting

Preterm birth is a primary outcome of interest in maternal vaccination trials but determination of gestational age is challenging in limited-resource settings. This study compares the New Ballard Score and fundal height measurements with the current standard of early ultrasound for sensitivity of predicting preterm birth. A trial of maternal influenza vaccination was conducted in Bamako, Mali. The New Ballard Score and fundal height were collected on 4038 infants born in the trial, ultrasound data were available for 1893 of those infants. New Ballard Score and fundal height were compared, consecutively, to all ultrasound results, early ultrasound results from the first trimester, and the date of last menstrual period for estimation of gestational age. Sensitivity of the New Ballard Score for identifying preterm infants was 0.33 compared with early ultrasound and 0.1 compared with the last menstrual period based estimates of gestational age. Sensitivity of low birth weight alone was 0.43 compared with early ultrasound. New Ballard Score estimated gestational age within 1 week of ultrasound more frequently than fundal height (53% compared with 7.6%, respectively) yet New Ballard Score identified few infants as preterm (1.8% vs 5.8% by early ultrasound), and was biased toward categorizing low birth weight infants and infants requiring hospitalization as preterm. New Ballard Score is not an ideal measure for identifying preterm births in low-resource settings. Despite the time and cost of training required for correct measurement of New Ballard Score, measurement of low birth weight alone performed better than New Ballard Score for identifying preterm infants.

Study protocol of a 4- parallel arm, superiority, community based cluster randomized controlled trial comparing paper and e-platform based interventions to improve accuracy of recall of last menstrual period (LMP) dates in rural Bangladesh

BACKGROUND

Gestational age (GA) is a key determinant of newborn survival and long-term impairment. Accurate estimation of GA facilitates timely provision of essential interventions to improve maternal and newborn outcomes. Menstrual based dating, ultrasound based dating, and neonatal estimates are the primarily used methods for assessing GA; all of which have some strength and weaknesses that require critical consideration. Last menstrual period (LMP) is simple, low-cost self-reported information, recommended by the World Health Organization for estimating GA but has issues of recall mainly among poorer, less educated women and women with irregular menstruation, undiagnosed abortion, and spotting during early pregnancy. Several studies have noted that about 20-50% of women cannot accurately recall the date of LMP. The goal of this study is therefore to improve recall and reporting of LMP and by doing so increase the accuracy of LMP based GA assessment in a rural population of Bangladesh where antenatal care-seeking, availability and utilization of USG is low.

METHOD

We propose to conduct a 4- parallel arm, superiority, community based cluster randomized controlled trial comparing three interventions to improve recall of GA with a no intervention arm. The interventions include (i) counselling and a paper based calendar (ii) counselling and a cell phone based SMS alert system (iii) counselling and smart-phone application. The trial is being conducted among 3360 adolescent girls and recently married women in Mirzapur sub-district of Bangladesh.

DISCUSSION

Enrolment of study participants continued from January 24, 2017 to March 29, 2017. Data collection and intervention implementation is ongoing and will end by February, 2019. Data analysis will measure efficacy of interventions in improving the recall of LMP date among enrolled participants. Results will be reported following CONSORT guideline. The innovative conventional & e-platform based interventions, if successful, can provide substantial evidence to scale-up in a low resource setting where m-Health initiatives are proliferating with active support from all sectors in policy and implementation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02944747 . The trial has been registered before starting enrolment on 24 October 2016.

Maternal concentrations of human chorionic gonadotrophin in very early IVF pregnancies and duration of pregnancy: a follow-up study

RESEARCH QUESTION

Are maternal concentrations of human chorionic gonadotropin (HCG) on a fixed day after embryo transfer associated with duration of pregnancy?

DESIGN

A follow-up study of 1917 singleton pregnancies after IVF was performed. Embryos were cultured for 2 days and maternal HCG concentration quantified on day 12 after embryo transfer. Duration of pregnancy was obtained from the Medical Birth Registry of Norway. Association of HCG concentration (log2-transformed) with duration of pregnancy was estimated as hazard ratios (HR) with 95% confidence intervals (CI) by applying Cox regression proportional hazard models, where time to delivery for pregnancies shortened because of planned Caesarean delivery or induction of labour was treated as censored.

RESULTS

The estimated median duration of pregnancy from embryo transfer was 266 days (95% CI 266-267 days). Maternal concentration of HCG on day 12 after embryo transfer varied from 1 to 588 IU/l (median 117 IU/l). Duration of pregnancy decreased by increasing HCG concentration, significantly in pregnancies delivered at full term ((257-270 days after embryo transfer; HR 1.127, 95% CI 1.026-1.238, P = 0.012). For each doubling of HCG concentration on day 12 after embryo transfer, duration of pregnancy was shortened by 0.51 days. Adjustment for maternal age, prepregnancy body mass index, being a first-time mother and number of embryos transferred did not change the association.

CONCLUSION

High maternal HCG concentration on a fixed day after embryo transfer is likely to indicate early embryo implantation. After embryo transfer, pregnancies with early implantation are shorter than pregnancies with late implantation.

Estimating recurrence and incidence of preterm birth subject to measurement error in gestational age: A hidden Markov modeling approach

Prediction of preterm birth as well as characterizing the etiological factors affecting both the recurrence and incidence of preterm birth (defined as gestational age at birth ≤ 37 wk) are important problems in obstetrics. The National Institute of Child Health and Human Development (NICHD) consecutive pregnancy study recently examined this question by collecting data on a cohort of women with at least 2 pregnancies over a fixed time interval. Unfortunately, measurement error due to the dating of conception may induce sizable error in computing gestational age at birth. This article proposes a flexible approach that accounts for measurement error in gestational age when making inference. The proposed approach is a hidden Markov model that accounts for measurement error in gestational age by exploiting the relationship between gestational age at birth and birth weight. We initially model the measurement error as being normally distributed, followed by a mixture of normals that has been proposed on the basis of biological considerations. We examine the asymptotic bias of the proposed approach when measurement error is ignored and also compare the efficiency of this approach to a simpler hidden Markov model formulation where only gestational age and not birth weight is incorporated. The proposed model is compared with alternative models for estimating important covariate effects on the risk of subsequent preterm birth using a unique set of data from the NICHD consecutive pregnancy study.

Counselling and management for anticipated extremely preterm birth

Counselling couples facing the birth of an extremely preterm infant is a complex and delicate task, entailing both challenges and opportunities. This revised position statement proposes using a prognosis-based approach that takes the best estimate of gestational age into account, along with additional factors, including estimated fetal weight, receipt of antenatal corticosteroids, singleton versus multiple pregnancy, fetal status and anomalies on ultrasound and place of birth. This statement updates data on survival in Canada, long-term neurodevelopmental disability at school age and quality of life, with focus on strategies to communicate effectively with parents. It also proposes a framework for determining the prognosis-based management option(s) to present to parents when initiating the decision-making process. This statement replaces the 2012 position statement.

Field testing of decision coaching with a decision aid for parents facing extreme prematurity

OBJECTIVE

The objective of this study is to assess and modify an existing decision aid and field-test decision coaching with the modified aid during consultations with parents facing potential delivery at 23 to 24 weeks gestation.

STUDY DESIGN

International Patient Decision Aid Standards instrument (IPDASi) scoring deficits, multi-stakeholder group feedback and α-testing guided modifications. Feasibility/acceptability were assessed. The Decisional Conflict Scale was used to measure participants' decisional conflict before (T1) and immediately after (T2) the consultation.

RESULTS

IPDASi assessment of the existing aid (score 11/35) indicated it required updated data, more information and a palliative care description. Following modification, IPDASi score increased to 26/35. Twenty subjects (12 pregnancies) participated in field-testing; 15 completed all questionnaires. Most participants (89%) would definitely recommend this form of consultation. Decisional conflict scores decreased (P<0.001) between T1 (52±25) and T2 (10±16).

CONCLUSION

Field testing demonstrated that consultations using the aid with decision coaching were feasible, reduced decisional conflict and may facilitate shared decision-making.

High birth weight and perinatal mortality among siblings: A register based study in Norway, 1967-2011

BACKGROUND

Perinatal mortality according to birth weight has an inverse J-pattern. Our aim was to estimate the influence of familial factors on this pattern, applying a cohort sibling design. We focused on excess mortality among macrosomic infants (>2 SD above the mean) and hypothesized that the birth weight-mortality association could be explained by confounding shared family factors. We also estimated how the participant's deviation from mean sibling birth weight influenced the association.

METHODS AND FINDINGS

We included 1 925 929 singletons, born term or post-term to mothers with more than one delivery 1967-2011 registered in the Medical Birth Registry of Norway. We examined z-score birth weight and perinatal mortality in random-effects and sibling fixed-effects logistic regression models including measured confounders (e.g. maternal diabetes) as well as unmeasured shared family confounders (through fixed effects models). Birth weight-specific mortality showed an inverse J-pattern, being lowest (2.0 per 1000) at reference weight (z-score +1 to +2) and increasing for higher weights. Mortality in the highest weight category was 15-fold higher than reference. This pattern changed little in multivariable models. Deviance from mean sibling birth weight modified the mortality pattern across the birth weight spectrum: small and medium-sized infants had increased mortality when being smaller than their siblings, and large-sized infants had an increased risk when outweighing their siblings. Maternal diabetes and birth weight acted in a synergistic fashion with mortality among macrosomic infants in diabetic pregnancies in excess of what would be expected for additive effects.

CONCLUSIONS

The inverse J-pattern between birth weight and mortality is not explained by measured confounders or unmeasured shared family factors. Infants are at particularly high mortality risk when their birth weight deviates substantially from their siblings. Sensitivity analysis suggests that characteristics related to maternal diabetes could be important in explaining the increased mortality among macrosomic infants.

Shared decision making for infants born at the threshold of viability: a prognosis-based guideline

OBJECTIVE

Making prenatal decisions regarding resuscitation of extremely premature infants, based on gestational age alone is inadequate. We developed a prognosis-based guideline.

STUDY DESIGN

We followed a five step approach and used the AGREE II framework: (1) systematic review and critical appraisal of published guidelines; (2) identification of key medical factors for decision making; (3) systematic reviews; (4) creation of a multi-disciplinary working group and (5) external consultation and appraisal.

RESULT

No published guideline met high-quality appraisal criteria. Survival, neurodevelopmental disability, quality of life of child and parents, and maternal mortality and risk of long-term morbidity were identified as key for quality decision-making. Eighteen stakeholders (including parents) advocated for the incorporation of parents' values and preferences in the process.

CONCLUSION

A novel framework, based on prognosis, was generated to guide when early intensive and palliative care may both be offered to expectant parents. Pre-implementation assessment is underway to identify barriers and facilitators to putting in practice.

Between-hospital variation in treatment and outcomes in extremely preterm infants

BACKGROUND

Between-hospital variation in outcomes among extremely preterm infants is largely unexplained and may reflect differences in hospital practices regarding the initiation of active lifesaving treatment as compared with comfort care after birth.

METHODS

We studied infants born between April 2006 and March 2011 at 24 hospitals included in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network. Data were collected for 4987 infants born before 27 weeks of gestation without congenital anomalies. Active treatment was defined as any potentially lifesaving intervention administered after birth. Survival and neurodevelopmental impairment at 18 to 22 months of corrected age were assessed in 4704 children (94.3%).

RESULTS

Overall rates of active treatment ranged from 22.1% (interquartile range [IQR], 7.7 to 100) among infants born at 22 weeks of gestation to 99.8% (IQR, 100 to 100) among those born at 26 weeks of gestation. Overall rates of survival and survival without severe impairment ranged from 5.1% (IQR, 0 to 10.6) and 3.4% (IQR, 0 to 6.9), respectively, among children born at 22 weeks of gestation to 81.4% (IQR, 78.2 to 84.0) and 75.6% (IQR, 69.5 to 80.0), respectively, among those born at 26 weeks of gestation. Hospital rates of active treatment accounted for 78% and 75% of the between-hospital variation in survival and survival without severe impairment, respectively, among children born at 22 or 23 weeks of gestation, and accounted for 22% and 16%, respectively, among those born at 24 weeks of gestation, but the rates did not account for any of the variation in outcomes among those born at 25 or 26 weeks of gestation.

CONCLUSIONS

Differences in hospital practices regarding the initiation of active treatment in infants born at 22, 23, or 24 weeks of gestation explain some of the between-hospital variation in survival and survival without impairment among such patients. (Funded by the National Institutes of Health.).

Placental abruption and subsequent risk of pre-eclampsia: a population-based case-control study

BACKGROUND

Pre-eclampsia and placental abruption may share a common pathophysiologic mechanism, namely, uteroplacental ischaemia. The aim of this study was to investigate the association between placental abruption and risk of pre-eclampsia in a subsequent pregnancy, and to determine whether the association differs by the gestational age at the time of abruption.

METHODS

A nested case-control study among multiparous women in the Medical Birth Register of Finland from 1996-2010 was conducted. Cases of pre-eclampsia (n = 6487) and frequency matched controls (n = 25,948) were linked to the Hospital Discharge Registry to ascertain data on prior abruption. Abruption was categorised as preterm (<37 weeks) or term (≥37 weeks) based on the gestational age at delivery. We fit logistic regression models to evaluate the associations between abruption and the odds of pre-eclampsia in the subsequent pregnancy before and after adjusting for potential confounders.

RESULTS

Preterm abruption was associated with over a twofold increase in risk of pre-eclampsia [odds ratio (OR) 2.2, 95% confidence interval (CI) 1.5, 3.3] in a subsequent pregnancy. In contrast, term abruption was not associated with pre-eclampsia (OR 1.1, 95% CI 0.7, 1.7). The association between preterm abruption and pre-eclampsia was further elevated among women with a history of pre-eclampsia. Associations with preterm abruption were also strengthened when the outcome was pre-eclampsia with early delivery (<34 weeks).

CONCLUSIONS

These findings suggest that placental abruption in a prior pregnancy is associated with a different risk profile of pre-eclampsia based on the gestational age of the abruption-affected pregnancy.

Determinants of number-specific recall error of last menstrual period: a retrospective cohort study

OBJECTIVE

To assess the digit preference for last menstrual period (LMP) dates, associated determinants and impact on obstetric outcome.

DESIGN

Retrospective cohort study.

SETTING

University medical centre (the Netherlands).

POPULATION

Cohort of 24 665 LMP records and a subgroup of 4630 cases with known crown-rump length (CRL) measurement, and obstetric outcome.

METHODS

Digit preference was determined by comparing the observed to expected counts of each day. Associated determinants were identified by multivariate regression analysis. Differences in obstetric outcome between LMP and CRL dating were analysed.

MAIN OUTCOME MEASURES

(Non)deprived neighbourhood, cycle irregularity, certainty of LMP date, maternal age, smoking, body mass index, parity and ultrasound investigator. Preterm and post-term delivery.

RESULTS

LMP digit preference for the first [odds ratio (OR), 1.28; 95% confidence interval (95% CI), 1.20-1.36], fifth (OR, 1.10; 95% CI, 1.03-1.17), 10th (OR, 1.17; 95% CI, 1.09-1.25), 15th (OR, 1.31; 95% CI, 1.23-1.40), 20th (OR, 1.22; 95% CI, 1.15-1.30) and 25th (OR, 1.08; 95% CI, 1.01-1.15) days of the month occurred more often than expected. Digit preference occurred more frequently in women living in a deprived neighbourhood (OR, 1.21; 95% CI, 1.06-1.39), with uncertain LMP (OR, 2.03; 95% CI, 1.63-2.52) or irregular cycle (OR, 1.24; 95% CI, 1.06-1.44). More post-term (≥42 weeks) deliveries (OR, 1.27; 95% CI, 1.05-1.54) were observed in LMP dating. This effect was larger in women with a digit preference (OR, 1.56; 95% CI, 1.03-2.37).

CONCLUSIONS

LMP digit preference occurs more often in women living in deprived neighbourhoods, with uncertain LMP or an irregular cycle. LMP-dated pregnancies are associated with more post-term pregnancies.

United States birth weight reference corrected for implausible gestational age estimates

OBJECTIVES

To provide an updated US birth weight for gestational age reference corrected for likely errors in last menstrual period (LMP)-based gestational age dating, as well as means and SDs, to enable calculation of continuous and categorical measures of birth weight for gestational age.

METHODS

From the 2009-2010 US live birth files, we abstracted singleton births between 22 and 44 weeks of gestation with at least 1 nonmissing estimate of gestational age (ie, LMP or obstetric/clinical) and birth weight. Using an algorithm based on birth weight and the concordance between these gestational age estimates, implausible LMP-based gestational age estimates were either excluded or corrected by using the obstetric/clinical estimate. Gestational age- and sex-specific birth weight means, SDs, and smoothed percentiles (3rd, 5th, 10th, 90th, 95th, 97th) were calculated, and the 10th and 90th percentiles were compared with published population-based references.

RESULTS

A total of 7 818 201 (99% of eligible) births were included. The LMP-based estimate of gestational age comprised 85% of the dataset, and the obstetric/clinical estimate comprised the remaining 15%. Cut points derived from the current reference identified ∼10% of births as ≤10th and ≥90th percentiles at all gestational weeks, whereas cut points derived from previous US-based references captured variable proportions of infants at these thresholds within the preterm and postterm gestational age ranges.

CONCLUSIONS

This updated US-based birth weight for gestational age reference corrects for likely errors in gestational age dating and allows for the calculation of categorical and continuous measures of birth size.

Improved birth weight for Black infants: outcomes of a Healthy Start program

OBJECTIVES

We determined whether participation in Healthy Babies Healthy Start (HBHS), a maternal health program emphasizing racial equity and delivering services through case management home visitation, was associated with improved birth outcomes for Black women relative to White women.

METHODS

We used a matched-comparison posttest-only design in which we selected the comparison group using propensity score matching. Study data were generated through secondary analysis of Michigan state- and Kalamazoo County-level birth certificate records for 2008 to 2010. We completed statistical analyses, stratified by race, using a repeated-measures generalized linear model.

RESULTS

Despite their smoking rate being double that of their matched counterparts, Black HBHS participants delivered higher birth-weight infants than did Black nonparticipants (P = .05). White HBHS participants had significantly more prenatal care than did White nonparticipants, but they had similar birth outcomes (P = .7 for birth weight; P = .55 for gestation).

CONCLUSIONS

HBHS participation is associated with increased birth weights among Black women but not among White women, suggesting differential program gains for Black women.

Placental abruption and placental weight - implications for fetal growth

OBJECTIVE

Placental abruption is associated with increased risks of preterm delivery and fetal growth restriction. As abruption is apparently a disease of the placenta, the extent to which abruption impacts the growth and development of the placenta remains poorly understood. We reasoned that a study of fetal growth and placental growth in relation to abruption might provide some clues to understanding the process through which placental abruption impacts fetal growth.

DESIGN

Multicenter, prospective cohort study.

SETTING

USA, 1959-1966.

POPULATION

A total of 38 684 pregnancies resulting in singleton live births (22-44 weeks).

MAIN OUTCOME MEASURES

Risk ratio of placental ratio <10th centile for gestational age in relation to abruption. Placental ratio was defined as the difference between placental weight and birthweight divided by birthweight (and expressed per 100 births).

RESULTS

Mean birthweight and placental weight were, on average, lower among abruption than nonabruption births, but this difference was observed only among births at <37 weeks. Births with placental ratio <10th centile were lower among abruption than nonabruption births at 22-36 weeks (risk ratio 0.4, 95% CI 0.2-0.8), but not at term (risk ratio 0.9, 95% CI 0.6-1.2).

CONCLUSIONS

In normal pregnancies, fetal weight and placental weight may operate under independent mechanisms, but in the presence of abruption, the associations appear largely through an interaction of both the maternal and fetal environments. This study underscores the importance of examining both the maternal and fetal compartments - and their interactions - to fully understand the consequences of abruption on fetal growth impairment.

Comparison of two measures of gestational age among low income births. The potential impact on health studies, New York, 2005

Recently, the National Association for Public Health Statistics and Information Systems considered changing the definition of gestational age from the current definition based on mother's last normal menstrual period (LMP) to the clinical/obstetric estimate determined by the physician (CE).They determined additional information was needed. This study provides additional insight into the comparability of the LMP and CE measures currently used on vital records among births at risk for poor outcomes. The data consisted of all New York State (NYS) (excluding New York City) singleton births in 2005 among mothers enrolled in the NYS Women Infants and Children (WIC) program during pregnancy. Prenatal WIC records were matched to NYS' Statewide Perinatal Data System. The analysis investigates differences between LMP and CE recorded gestations. Relative risks between risk factors and preterm birth were compared for LMP and CE. Exact agreement between gestation measures exists in 49.6% of births. Overall, 6.4% of records indicate discordance in full term/preterm classifications; CE is full term and LMP preterm in 4.9%, with the converse true for 1.5%. Associations between risk factor and preterm birth differed in magnitude based on gestational age measurement. Infants born to mothers with high risk indicators were more likely to have a CE of preterm and LMP full term. Changing the measure of gestational age to CE universally likely would result in overestimation of the importance of some risk factors for preterm birth. Potential overestimation of clinical outcomes associated with preterm birth may occur and should be studied.

Early life factors and risk of childhood rhabdomyosarcoma

Although little is known about etiology of childhood rhabdomyosarcoma (RMS), early life factors are suspected in the etiology. We explored this hypothesis using linked data from the California Cancer Registry and the California birth rolls. Incident cases were 359 children <6-year-old (218 embryonal, 81 alveolar, 60 others) diagnosed in 1988-2008. Controls (205, 173), frequency matched on birth year (1986-2007), were randomly selected from the birth rolls. We examined association of birth characteristics such as birth weight, size for gestational age, and timing of prenatal care with all-type RMS, embryonal, and alveolar subtypes. Crude and adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated using logistic regression. In contrast to a previous study, we observed statistically non-significant association for embryonal subtype among high birth weight (4000-5250 g) children for term births [OR (95% CI): 1.28 (0.85, 1.92)] and all births adjusted for gestational age [OR (95% CI): 1.21 (0.81, 1.81)]. On the other hand, statistically significant 1.7-fold increased risk of alveolar subtype (95% CI: 1.02, 2.87) was observed among children with late or no prenatal care and a 1.3-fold increased risk of all RMS subtypes among children of fathers ≥35 years old at child birth (95% CI: 1.00, 1.75), independent of all covariates. Our finding of positive association on male sex for all RMS types is consistent with previous studies. While we did not find a convincingly positive association between high birth weight and RMS, our findings on prenatal care supports the hypothesis that prenatal environment modifies risk for childhood RMS.

Rate of detection of unsuspected pregnancies after implementation of mandatory point-of-care urine pregnancy testing prior to hysterosalpingography

PURPOSE

The aim of this study was to determine the rate of detection of unsuspected pregnancies after the implementation of mandatory point-of-care urine pregnancy testing before hysterosalpingography (HSG).

METHODS

At the authors' institution, HSGs are scheduled to occur during days 8 to 12 of the menstrual cycle. Upon arrival in the radiology department, all women undergo point-of-care urine pregnancy testing before HSG (at a cost of $1.25 per test). Urine pregnancy test results were retrospectively reviewed.

RESULTS

Four hundred ten women (mean age, 25.9 years; range, 22-50 years) underwent point-of-care urine pregnancy testing before HSG between October 2010 and July 2012. Study indications were infertility evaluation (90.7% [372 of 410]) and tubal patency assessment after placement of tubal occlusive devices (9.3% [38 of 410]). Two positive urine pregnancy test results (0.5%) were recorded. One positive result was deemed a false-positive because the patient had received an intramuscular injection of β-human chorionic gonadotropin before the scheduled HSG, and follow-up laboratory testing showed declining β-human chorionic gonadotropin levels. The second positive result was a true-positive, and the patient was determined to be 4.5 weeks pregnant on the date of the scheduled HSG.

CONCLUSIONS

One of 410 women presenting for HSG was found to have an unsuspected early pregnancy, which was detected with a point-of-care urine pregnancy test. Consideration should be given to routine pregnancy testing of women before HSG because scheduling on the basis of menstrual cycle dates can be unreliable.

Determining gestational age for public health care users in Brazil: comparison of methods and algorithm creation

BACKGROUND

A valid, accurate method for determining gestational age (GA) is crucial in classifying early and late prematurity, and it is a relevant issue in perinatology. This study aimed at assessing the validity of different measures for approximating GA, and it provides an insight into the development of algorithms that can be adopted in places with similar characteristics to Brazil. A follow-up study was carried out in two cities in southeast Brazil. Participants were interviewed in the first trimester of pregnancy and in the postpartum period, with a final sample of 1483 participants after exclusions. The distribution of GA estimates at birth using ultrasound (US) at 21-28 weeks, US at 29+ weeks, last menstrual period (LMP), and the Capurro method were compared with GA estimates at birth using the reference US (at 7-20 weeks of gestation). Kappa, sensitivity, and specificity tests were calculated for preterm (<37 weeks of gestation) and post-term (>=42 weeks) birth rates. The difference in days in the GA estimates between the reference US and the LMP and between the reference US and the Capurro method were evaluated in terms of maternal and infant characteristics, respectively.

RESULTS

For prematurity, US at 21-28 weeks had the highest sensitivity (0.84) and the Capurro method the highest specificity (0.97). For postmaturity, US at 21-28 weeks and the Capurro method had a very high sensitivity (0.98). All methods of GA estimation had a very low specificity (≤0.50) for postmaturity. GA estimates at birth with the algorithm and the reference US produced very similar results, with a preterm birth rate of 12.5%.

CONCLUSIONS

In countries such as Brazil, where there is less accurate information about the LMP and lower coverage of early obstetric US examinations, we recommend the development of algorithms that enable the use of available information using methodological strategies to reduce the chance of errors with GA. Thus, this study calls into attention the care needed when comparing preterm birth rates of different localities if they are calculated using different methods.

Is short first-trimester crown-rump length associated with spontaneous preterm birth?

OBJECTIVE

To assess the association between first-trimester crown-rump length (CRL) and the risk of spontaneous preterm birth before 32 weeks' gestation.

METHODS

We performed a matched case-control study of 129 women with spontaneous preterm birth at < 32 weeks' gestation (cases) and 129 women with term deliveries (controls) using data stored in the ultrasound and obstetric databases of our tertiary referral center. Cases and controls were individually matched based on maternal age, parity, history of preterm birth and medical indication for antenatal care. Fetal CRL measured between 8 + 0 and 13 + 6 weeks was expressed as multiples of the median (MoM) expected CRL, based on last menstrual period. We investigated the association between CRL-MoM and spontaneous preterm birth using logistic regression analysis.

RESULTS

CRL-MoM was not associated with spontaneous preterm birth: odds ratio (OR) 1.10 (95% CI, 0.89-1.36) per 0.10 MoM increase in CRL. Timing of measurement did not influence the model (P = 0.59). This was confirmed when restricting the analysis to the 93 pairs with CRL measurements made between 10 + 0 and 13 + 6 weeks: OR for preterm birth 1.07 (95% CI, 0.83-1.37) per 0.10 MoM increase in CRL.

CONCLUSION

A short CRL in the first trimester is not associated with spontaneous preterm birth before 32 weeks' gestation, thus short CRL cannot be used to identify women at increased risk of preterm birth.

Using mixture models with linear predictors to identify incorrect gestational age in state birth records

BACKGROUND

Birthweight distributions for early last-menstrual-period-based gestational ages are bimodal, and some birthweights in the right-side distribution are implausible for the specified gestational age. Mixture models can be used to identify births in the right-side distribution. The objective of this study was to determine which maternal and infant factors to include in the mixture models to obtain the best fitting models for New Jersey state birth records.

METHODS

We included covariates in the models as linear predictors of the means of the component distributions and the proportion of births in each component. This allowed both the means and the proportions to vary across levels of the covariates.

RESULTS

The final model included maternal age and timing of entry into prenatal care. The proportion of births in the right-side distribution was lowest for older mothers who entered prenatal care early, higher for teen mothers who entered prenatal care early, higher still for older mothers who entered prenatal care late, and highest for teens who entered prenatal care late. Over 44% of births were classified as incorrect reported gestational age.

CONCLUSION

These results suggest that (1) including these two covariates as linear predictors of the means and mixing proportions gives the best model for identifying births with incorrect reported gestational age, (2) late entry into prenatal care is a mechanism by which erroneously short last-menstrual-period-based gestational ages are generated, and (3) including linear predictors of the mixing proportions in the model increases the validity of the classification of incorrect reported gestational age.

A mixture model to correct misclassification of gestational age

PURPOSE

Misclassification of gestational age based on the last menstrual period (LMP) in routinely collected data creates bias in newborn birthweight and gestational age-related indicators. Common correction methods have not been evaluated. We developed a normal mixture model for use with SAS software to correct misclassification of gestational age and compare its performance with other available correction methods and estimates of gestational age.

METHODS

Using the 2007 United States natality file from the National Center for Health Statistics, we compared LMP preterm and postterm birth rates and gestational age-specific birthweight percentiles against a reference subset of births, where the likelihood of misclassification in gestational age was minimized, before and after correction by a normal mixture model, two truncation methods, and the clinical/obstetric estimate of gestational age.

RESULTS

The mixture model corrected preterm and postterm birth rates by 90% and 41% respectively, but previous methods performed poorly. The mixture model was also superior in correcting birthweight percentiles 50 and 90 with error reductions in the range of 68% to 85% between 28 and 36 weeks of gestation, where most misclassification occurred.

CONCLUSIONS

The mixture model behaved consistently better than truncation methods, particularly between weeks 28 and 36 of gestation.

Challenges in defining and classifying the preterm birth syndrome

In 2009, the Global Alliance to Prevent Prematurity and Stillbirth Conference charged the authors to propose a new comprehensive, consistent, and uniform classification system for preterm birth. This first article reviews issues related to measurement of gestational age, clinical vs etiologic phenotypes, inclusion vs exclusion of multifetal and stillborn infants, and separation vs combination of pathways to preterm birth. The second article proposes answers to the questions raised here, and the third demonstrates how the proposed system might work in practice.

Trends in cesarean delivery at preterm gestation and association with perinatal mortality

OBJECTIVE

We sought to examine the extent to which a temporal increase in preterm cesarean delivery is associated with gestational age-specific changes in perinatal survival in preterm gestations.

STUDY DESIGN

We utilized data on singleton births in the United States (1990 through 2004) delivered between 24-36 weeks' gestation. Associations between changes in cesarean delivery at preterm gestations and trends in the risk of preterm stillbirth, and neonatal and perinatal mortality were estimated before and after adjustments for a variety of potential confounders.

RESULTS

From 1990 through 2004, cesarean delivery rates increased by 50.6%, 40.7%, and 35.8% at 24-27, 28-33, and 34-36 weeks, respectively. The largest incremental effect of cesarean was associated with a reduction in stillbirths by 5.8%, 14.2%, and 23.1% at 24-27, 28-33, and 34-36 weeks, respectively, leading to an 11.4%, 4.9%, and 0.6% reduction in perinatal deaths at 24-27, 28-33, and 34-36 weeks, respectively.

CONCLUSION

Increasing rates of preterm cesarean were associated with improved perinatal survival. This association was evident largely because of dramatic incremental declines in stillbirths.

Home pregnancy test compared to standard-of-care ultrasound dating in the assessment of pregnancy duration

OBJECTIVE

To determine the level of agreement between the Clearblue Digital Pregnancy Test with Conception Indicator home pregnancy test and standard-of-care ultrasound in assessing pregnancy duration in a real-life, observational setting encompassing routine, clinical care.

RESEARCH DESIGN AND METHODS

This was a prospective observational study of non-pregnant women seeking conception. Women collected daily urine samples from day 1 of their next menstrual cycle. If any volunteer became pregnant, daily urine samples continued to be collected for 43 days after the LH surge. Samples from day -7 to day +28 relative to the expected period (LH surge + 15 days) were tested using the home pregnancy test. This categorised any resulting pregnancies into one of three groups: 1-2 weeks, 2-3 weeks, and 3+ weeks since conception. Information from the standard UK ultrasound dating scan was also recorded by the midwife, including the expected delivery date according to ultrasound and the expected delivery date according to LMP.

MAIN OUTCOME MEASURES

Full data were available from 52 pregnant women who had conceived naturally. During the study analysis, 4786 urine samples were cross-compared with 52 routine 12-week NHS ultrasound assessments and the level of agreement between home pregnancy testing and standard-of-care ultrasound in determining pregnancy duration was calculated.

RESULTS

The agreement between the gestational age as calculated by the home pregnancy test result and the exact midwife-recorded gestational age using ultrasound was 82.3%. However, when a ± 5-day range was applied to the ultrasound reading (as per routine UK clinical practice), the level of agreement was 98%.

CONCLUSIONS

The home pregnancy test provides a significantly high (98%) level of agreement with standard-of-care ultrasound when assessing pregnancy duration in a real-life, observational setting which closely mirrors daily clinical practice.

Ischemic placental disease: maternal versus fetal clinical presentations by gestational age

OBJECTIVE

Preeclampsia, small for gestational age (SGA), and abruption are considered ischemic placental diseases (IPD), and are major contributors to both maternal and fetal morbidity and mortality. Although the placenta is considered a fetal organ, these conditions can present clinically with either maternal or fetal manifestations, but their relationship to preterm births is largely unexplored.

METHODS

We designed a population-based study to assess the origins of IPD. IPD was classified as maternal (preeclampsia only), fetal (SGA only), or both (abruption only, preeclampsia with either SGA or abruption, or all 3). The study was based on 90,500 women that delivered singleton live births at 22-44 weeks gestation.

RESULTS

Among 77,275 term births with IPD, 23.2% presented as maternal disease only, 68.9% as fetal disease, and 7.9% as both. In contrast, among 12,906 preterm births with IPD, the proportions were roughly equal (maternal 32.9%, fetal 36.5%, and both 30.6%). Among spontaneous preterm births with IPD, a greater proportion had a fetal presentation (43.0%), whereas among indicated preterm births with IPD, a greater proportion (43.4%) had both maternal and fetal presentations.

CONCLUSIONS

IPD at preterm gestations is more likely to involve both the mother and fetus than at term. The differing clinical presentations by gestational age suggest different pathways between term and preterm births. This may reflect heterogeneous processes for IPD at early vs. late gestations, regardless of the effects of differing gestational age thresholds for interventions.

Patterns and predictors of vaginal bleeding in the first trimester of pregnancy

PURPOSE

Although first-trimester vaginal bleeding is an alarming symptom, few studies have investigated the prevalence and predictors of early bleeding. This study characterizes first trimester bleeding, setting aside bleeding that occurs at time of miscarriage.

METHODS

Participants (n = 4539) were women ages 18 to 45 enrolled in Right From the Start, a community-based pregnancy study (2000-2008). Bleeding information included timing, heaviness, duration, color, and associated pain. Life table analyses were used to describe gestational timing of bleeding. Factors associated with bleeding were investigated by the use of multiple logistic regression with multiple imputation for missing data.

RESULTS

Approximately one fourth of participants (n = 1207) reported bleeding (n = 1656 episodes), but only 8% of women with bleeding reported heavy bleeding. Of the spotting and light bleeding episodes (n = 1555), 28% were associated with pain. Among heavy episodes (n = 100), 54% were associated with pain. Most episodes lasted less than 3 days, and most occurred between gestational weeks 5 to 8. Twelve percent of women with bleeding and 13% of those without experienced miscarriage. Maternal characteristics associated with bleeding included fibroids and prior miscarriage.

CONCLUSIONS

Consistent with the hypothesis that bleeding is a marker for placental dysfunction, bleeding is most likely to be observed around the time of the luteal-placental shift.

Undiagnosed coeliac disease in a father does not influence birthweight and preterm birth

There is conflicting evidence regarding the effect of coeliac disease (CD) in the father on birthweight and preterm birth. We investigated the association between paternal CD and birthweight and preterm birth. Medical records of all singleton live-born children in Denmark between 1 January 1979 and 31 December 2004 were linked to information about parents' diseases. Fathers who were diagnosed with CD were then identified. Fathers with CD were considered treated if they were diagnosed before pregnancy and untreated if they were diagnosed after the date of conception. The outcome measures were: birthweight, small-for-gestational age (birthweight<10th centile for gestational age) and preterm birth (<37 weeks). We compared the offspring of men without CD (n = 1 472 352) and offspring of those with CD [untreated (n = 138) and treated (n = 473)]. There was no significant association between untreated CD in the father and birthweight (adjusted mean difference = -3 g; [95% CI -46, 40]) or preterm birth (adjusted odds ratio (OR) = 0.86, [95% CI 0.53, 1.37]) (compared with no CD). There was some evidence for an association between treated paternal CD and birthweight (adjusted mean difference = -81 g; [95% CI -161, -3]), but not preterm birth (adjusted OR = 1.76, [95% CI 0.95, 3.26]). Untreated paternal CD was not associated with an increased risk of reduced birthweight, or of preterm birth. There was some evidence that diagnosis and presumed treatment of paternal CD with a gluten-free diet is associated with reduced birthweight.

Impact of pregnancy-induced hypertension on stillbirth and neonatal mortality

BACKGROUND

Hypertensive disorders of pregnancy are more frequent in primiparous women, but may be more severe in multiparas. We examined trends in stillbirth and neonatal mortality related to pregnancy-induced hypertension (PIH), and explored whether mortality varied by parity and maternal race.

METHODS

We carried out a population-based study of 57 million singleton live births and stillbirths (24-46 weeks' gestation) in the United States between 1990 and 2004. We estimated rates and adjusted odds ratios (ORs) of stillbirth and neonatal death in relation to PIH, comparing births in 1990-1991 with 2003-2004.

RESULTS

PIH increased from 3.0% in 1990-1991 to 3.8% in 2003-2004. In both periods, PIH was associated with a higher risk of stillbirth and neonatal death. We explored this in more detail in 2003-2004, and observed that the increased risk of PIH-related stillbirth was higher in women having their second or higher-order births (OR = 2.2 [95% confidence interval = 2.1-2.4]) compared with women having their first birth (1.5 [1.4-1.6]). Patterns were similar for neonatal death (1.3 [1.2-1.4] in first and 1.6 [1.5-1.8] in second or higher-order births). Among multiparas, the association between PIH and stillbirth was stronger in black women (2.9 [2.7-3.2]) than white women (2.0 [1.8-2.1]).

CONCLUSIONS

A substantial burden of stillbirth and neonatal mortality is associated with PIH, especially among multiparous women, which may be due to more severe PIH, or to a higher burden of underlying disease.

Characteristics of prospectively measured vaginal bleeding among women trying to conceive

MikolajczykPrevious research has described variability in menstrual cycle lengths within and across women, though less attention has focused on characterising patterns of bleeding. While clinical definitions for menstrual bleeding are often given in standard textbooks, the validity of conventional definitions has not been empirically evaluated in epidemiological studies. The definition of menstrual bleeding may affect the analysis of time to pregnancy and pregnancy dating that relies upon the last menstrual period. We used daily records of vaginal bleeding from a prospective cohort study that included 74 women trying to become pregnant who reported 430 bleeding episodes. A longitudinal mixture model (PROC TRAJ) was used to classify patterns of bleeding. Among the first 74 bleeding episodes, 15% comprised only days with spotting or light bleeding (possibly representing non-menstrual bleeding given the length of the cycle defined by these bleeding episodes). When all 430 bleeding episodes were analysed, four distinct bleeding patterns emerged: (1) episodic bleeding comprising 1-3 days of spotting (10%), (2) bleeding lasting 3-6 days (40%), (3) bleeding lasting 6-8 days (33%), and (4) bleeding lasting 8-12 days (17%). These findings suggest that non-menstrual bleeding may be relatively common. Considerable variation in menstrual bleeding patterns is evident, and as such is likely to impact fecundity-related endpoints or gestational age estimates that rely upon menstrual cycle dates. The association between bleeding patterns and female fecundity awaits future research.

The impact of maternal celiac disease on birthweight and preterm birth: a Danish population-based cohort study

BACKGROUND

Adverse pregnancy outcomes have been associated with maternal celiac disease (CD). In this study, we investigate the effect of treated and untreated maternal CD on infant birthweight and preterm birth.

METHODS

A population-based cohort study consisted of all singleton live births in Denmark between 1 January 1979 and 31 December 2004 was used. A total of 1,504,342 babies were born to 836,241 mothers during the study period. Of those, 1105 babies were born to women with diagnosed CD and 346 were born to women with undiagnosed CD. Women with diagnosed CD were considered as treated with a gluten free diet while women with undiagnosed CD were considered as untreated. The outcome measures were: birthweight, small for gestational age (SGA: birthweight <10th centile), very small for gestational age (VSGA: birthweight <5th centile) and preterm birth. We compared these measures in treated and untreated women with those of a reference group (no history of CD).

RESULTS

Women with untreated CD delivered smaller babies [difference = -98 g (95% CI: -130, -67)], with a higher risk of SGA infants [OR = 1.31 (95% CI: 1.06, 1.63)], VSGA infants [OR = 1.54 (95% CI: 1.17, 2.03)] and preterm birth [OR = 1.33 (95% CI: 1.02, 1.72)] compared with women without CD. Women with treated CD had no increased risk of reduced mean birthweight, risk of delivering SGA and VSGA infants or preterm birth compared with women without CD.

CONCLUSION

Untreated maternal CD increases the risk of reduced birthweight, the risk of delivering SGA and VSGA infants and preterm birth. Diagnosis and presumed treatment of maternal CD with a gluten-free diet appeared to result in a birthweight and preterm birth rate similar to those in women without CD.

Distinguishing pathological from constitutional small for gestational age births in population-based studies

BACKGROUND

Small for gestational age (SGA) can occur following a pathological process or may represent constitutionally small fetuses. However, distinguishing these processes is often difficult, especially in large studies, where the term SGA is often used as a proxy for restricted fetal growth. Since biologic variation in fetal size is largely a third trimester phenomenon, we hypothesized that the definition of SGA at term may include a sizeable proportion of constitutionally small fetuses. In contrast, since biologic variation in fetal size is not fully expressed in (early) preterm gestations, it is plausible that SGA in early preterm gestations would comprise a large proportion of growth restricted fetuses.

AIM

We compared mortality and morbidity rates between SGA and appropriate for gestational age (AGA) babies.

SUBJECTS

A population-based study of over 19million non-malformed, singleton births (1995-04) in the United States was performed. Gestational age (24-44weeks) was based on a clinical estimate. SGA and AGA were defined as sex-specific birthweight <10th and 25-74th centiles, respectively, for gestational age. All analyses were adjusted for a variety of confounding factors.

OUTCOME MEASURES

Excess mortality risk in SGA and AGA babies.

RESULTS

On an additive scale, stillbirth and neonatal mortality rates were higher at every preterm gestation among SGA than AGA births, and similar at term gestations. An inverse relationship between gestational age and excess deaths between SGA and AGA babies delivered at <37weeks was evident.

CONCLUSIONS

In early preterm gestations, the definition of SGA may well be justified as a proxy for IUGR. In contrast, SGA babies that are delivered at term are likely to be constitutionally small.

Primiparity: An ‘intermediate’ risk group for spontaneous and medically indicated preterm birth

OBJECTIVE

Most women in their first pregnancy are at 'unknown' risk for preterm birth. We hypothesized that such women may be at an increased risk for preterm birth in comparison to those with a prior term birth.

METHODS

We used Missouri's maternally-linked data (1989-97), comprised of women delivering their first singleton live birth (N = 259 431) and women delivering their first two consecutive singleton live births (N = 154 810). We compared preterm birth (<37 weeks) rates among women with a previous term birth, women with no reproductive history (primiparous women), and in those with a previous preterm birth. Risks of spontaneous and medically indicated preterm birth were also examined after adjustments for confounders through multivariate log-binomial regression models.

RESULTS

Preterm birth rates were 8.1%, 9.6%, and 23.3% among women with a previous term birth, among primiparous women, and among those with a previous preterm birth, respectively. In comparison to women with a prior term birth, risks of spontaneous preterm birth among primiparous women and among women with a prior preterm birth were 1.1-fold (95% confidence interval (CI) 1.0, 1.2) and 2.5-fold (95% CI 2.4, 2.6) higher, respectively. These risks were higher for medically indicated preterm birth among both primiparous women (RR 1.3, 95% CI 1.2, 1.4) and those with a prior preterm birth (RR 3.2, 95% CI 3.0, 3.5) than for spontaneous preterm births.

CONCLUSIONS

Primiparous women are at increased risk of both medically indicated and spontaneous preterm birth. The findings suggest that studies on preterm birth should consider a risk assignment to include three groups: low-risk (prior term birth), intermediate risk (primiparity), and high-risk (prior preterm birth). This strategy will be informative for the identification of women with impending risk of delivering preterm, and complications associated with prematurity.

The effect of exclusion of cases with unrecorded best estimate of gestational age on the estimates of preterm birth rate

OBJECTIVES

To investigate the effect of excluding cases with unrecorded best estimate of gestational age at birth on pregnancy outcome reporting and to determine the reasons for unrecorded gestational age data.

DESIGN

Prospective study.

SETTING

Fifteen maternity units in North West London.

POPULATION

497,105 women who booked for antenatal care from 1988 to 1998.

METHOD

Multiple logistic regression analysis.

MAIN OUTCOME MEASURES

Preterm birth rate of, and the factors associated with, cases with unrecorded best estimate of gestational age at birth.

RESULTS

Of the 53,981 cases with an unrecorded best estimate of gestational age at birth, by using additional data, it was possible to compute a new best estimate of gestational age in 80%. In this latter group, the preterm birth rate was 42% (95% CI 41.5-42.6). The corrected, overall preterm birth rate in North West London (9.8%, 9.7-9.9) was higher than the original estimate (7.6%, 7.5-7.7), which included only cases with recorded data on gestational age at birth. The most significant factors associated with an unrecorded gestational age were no ultrasound scan (OR 49, P < 0.001), and preterm birth <31 weeks (OR 30, P < 0.001).

CONCLUSIONS

The incidence of preterm birth are likely to be under-reported in studies where only cases with readily available gestational age data are included. In routinely collected maternity data, human omission is an important contributing factor for an unrecorded best estimate of gestational age at birth. This is associated with the urgent transfer of babies to the neonatal intensive care unit.

Rates of preterm birth following antenatal maternal exposure to severe life events: a population-based cohort study

BACKGROUND

Preterm birth and other pregnancy complications have been linked to maternal stress during pregnancy. We investigated the association between maternal exposure to severe life events and risk of preterm birth.

METHODS

Mothers of all singleton live births (n = 1.35 million births) in Denmark between 1 January 1979 and 31 December 2002 were linked to data on their children, parents, siblings and partners. We defined exposure as death or serious illness in close relatives in the first or second trimesters or in the 6 months before conception. Log-linear binomial regression was used to estimate the effect of exposure on preterm birth, very preterm birth and extremely preterm birth.

RESULTS

There were 58 626 (4.34%) preterm births (<37 weeks), 11 732 (0.87%) very preterm births and 3288 (0.24%) extremely preterm births in the study cohort. Severe life events in close relatives in the 6 months before conception increased the risk of preterm birth by 16% (relative risk, RR = 1.16, [95% CI: 1.08-1.23]). Severe life events in older children in the 6 months before conception increased the risk of preterm birth by 23% (RR = 1.23, [95% CI: 1.02-1.49]) and the risk of very preterm birth by 59% (RR = 1.59, [95% CI: 1.08-2.35]).

CONCLUSIONS

Our population-based cohort study suggests that maternal exposure to severe life events, particularly in the 6 months before pregnancy, may increase the risk of preterm and very preterm birth.

Comparison of gestational age at birth based on last menstrual period and ultrasound during the first trimester

Reported last menstrual period (LMP) is commonly used to estimate gestational age (GA) but may be unreliable. Ultrasound in the first trimester is generally considered a highly accurate method of pregnancy dating. The authors compared first trimester report of LMP and first trimester ultrasound for estimating GA at birth and examined whether disagreement between estimates varied by maternal and infant characteristics. Analyses included 1867 singleton livebirths to women enrolled in a prospective pregnancy cohort. The authors computed the difference between LMP and ultrasound GA estimates (GA difference) and examined the proportion of births within categories of GA difference stratified by maternal and infant characteristics. The proportion of births classified as preterm, term and post-term by pregnancy dating methods was also examined. LMP-based estimates were 0.8 days (standard deviation = 8.0, median = 0) longer on average than ultrasound estimates. LMP classified more births as post-term than ultrasound (4.0% vs. 0.7%). GA difference was greater among young women, non-Hispanic Black and Hispanic women, women of non-optimal body weight and mothers of low-birthweight infants. Results indicate first trimester report of LMP reasonably approximates gestational age obtained from first trimester ultrasound, but the degree of discrepancy between estimates varies by important maternal characteristics.

A population-based study of craniosynostosis in metropolitan Atlanta, 1989-2003

Craniosynostosis is a birth defect characterized by premature fusion of one or more cranial sutures. We describe the birth prevalence of craniosynostosis and related risk factors among infants born to residents of metropolitan Atlanta during 1989-2003. Data from the Metropolitan Atlanta Congenital Defects Program (MACDP) were used to identify infants with craniosynostosis. Case records with a code for craniosynostosis were reviewed to substantiate the diagnosis of craniosynostosis and to classify infants as having isolated craniosynostosis (no other unrelated major defects), multiple defects (one or more additional major, unrelated defects), or a syndrome (recognized or strongly suspected single-gene condition or chromosome abnormality). Vital records data on births of Georgia residents were used to analyze craniosynostosis prevalence by year of birth, maternal race and age, parity, plurality, and infants' sex, birth weight, and gestational age. We identified 281 infants born with craniosynostosis in metropolitan Atlanta during 1989-2003: 84% with isolated craniosynostosis, 7% with multiple defects, and 9% with syndromes. The birth prevalence was 4.3 per 10,000 births, results consistent with findings from other population-based studies using similar case definitions. Apert syndrome was diagnosed in 40% of the syndromic cases, and sagittal synostosis was diagnosed in 39% of the cases of nonsyndromic craniosynostosis. Maternal age 35 years or older, multiple birth, male sex, and birth weight >4,000 g were risk factors for craniosynostosis.

Intensive care for extreme prematurity--moving beyond gestational age

BACKGROUND

Decisions regarding whether to administer intensive care to extremely premature infants are often based on gestational age alone. However, other factors also affect the prognosis for these patients.

METHODS

We prospectively studied a cohort of 4446 infants born at 22 to 25 weeks' gestation (determined on the basis of the best obstetrical estimate) in the Neonatal Research Network of the National Institute of Child Health and Human Development to relate risk factors assessable at or before birth to the likelihood of survival, survival without profound neurodevelopmental impairment, and survival without neurodevelopmental impairment at a corrected age of 18 to 22 months.

RESULTS

Among study infants, 3702 (83%) received intensive care in the form of mechanical ventilation. Among the 4192 study infants (94%) for whom outcomes were determined at 18 to 22 months, 49% died, 61% died or had profound impairment, and 73% died or had impairment. In multivariable analyses of infants who received intensive care, exposure to antenatal corticosteroids, female sex, singleton birth, and higher birth weight (per each 100-g increment) were each associated with reductions in the risk of death and the risk of death or profound or any neurodevelopmental impairment; these reductions were similar to those associated with a 1-week increase in gestational age. At the same estimated likelihood of a favorable outcome, girls were less likely than boys to receive intensive care. The outcomes for infants who underwent ventilation were better predicted with the use of the above factors than with use of gestational age alone.

CONCLUSIONS

The likelihood of a favorable outcome with intensive care can be better estimated by consideration of four factors in addition to gestational age: sex, exposure or nonexposure to antenatal corticosteroids, whether single or multiple birth, and birth weight. (ClinicalTrials.gov numbers, NCT00063063 [ClinicalTrials.gov] and NCT00009633 [ClinicalTrials.gov].).

Estimation of individual neonatal survival using birthweight and gestational age: a way to improve neonatal care

The study was conducted to determine the combined effect of birthweight and gestational age at birth on neonatal mortality using individually-identified livebirths. Logistic regression was used for studying the interactive effect of birthweight and gestational age on the individual probability of neonatal death. All livebirths from Chile in 2000 were included in a linked file. Odds ratio models for birthweight and gestational age were developed for each sex. The probability of neonatal death by sex was presented using contour plots. The models were statistically significant, and odds ratios were different and non-linear for the effects of birthweight and gestational age. Contour plots of constant neonatal mortality according to birthweight and gestational age were presented; they were similar for each sex. A single graph for both sexes that estimates the survival potential of infants born too early or too small would improve neonatal care in developing countries.

Assessing fetal growth impairments based on family data as a tool for identifying high-risk babies. An example with neonatal mortality

Background

Low birth weight is associated with an increased risk of neonatal and infant mortality and morbidity, as well as with other adverse conditions later in life. Since the birth weight-specific mortality of a second child depends on the birth weight of an older sibling, a failure to achieve the biologically intended size appears to increase the risk of adverse outcome even in babies who are not classified as small for gestation. In this study, we aimed at quantifying the risk of neonatal death as a function of a baby's failure to fulfil its biologic growth potential across the whole distribution of birth weight.

Methods

We predicted the birth weight of 411,957 second babies born in Denmark (1979–2002), given the birth weight of the first, and examined how the ratio of achieved birth weight to predicted birth weight performed in predicting neonatal mortality.

Results

For any achieved birth weight category, the risk of neonatal death increased with decreasing birth weight ratio. However, the risk of neonatal death increased with decreasing birth weight, even among babies who achieved their predicted birth weight.

Conclusion

While a low achieved birth weight was a stronger predictor of mortality, a failure to achieve the predicted birth weight was associated with increased mortality at virtually all birth weights. Use of family data may allow identification of children at risk of adverse health outcomes, especially among babies with apparently "normal" growth.

Multiple imputation for national public-use datasets and its possible application for gestational age in United States Natality files

Multiple imputation (MI) is a technique that can be used for handling missing data in a public-use dataset. With MI, two or more completed versions of the dataset are created, containing possibly different but reasonable replacements for the missing data. Users analyse the completed datasets separately with standard techniques and then combine the results using simple formulae in a way that allows the extra uncertainty due to missing data to be assessed. An advantage of this approach is that the resulting public-use data can be analysed by a variety of users for a variety of purposes, without each user needing to devise a method to deal with the missing data. A recent example for a large public-use dataset is the MI of the family income and personal earnings variables in the National Health Interview Survey. We propose an approach to utilise MI to handle the problems of missing gestational ages and implausible birthweight-gestational age combinations in national vital statistics datasets. This paper describes MI and gives examples of MI for public-use datasets, summarises methods that have been used for identifying implausible gestational age values on birth records, and combines these ideas by setting forth scenarios for identifying and then imputing missing and implausible gestational age values multiple times. Because missing and implausible gestational age values are not missing completely at random, using multiple imputations and, thus, incorporating both the existing relationships among the variables and the uncertainty added from the imputation, may lead to more valid inferences in some analytical studies than simply excluding birth records with inadequate data.

Menstrual versus clinical estimate of gestational age dating in the United States: temporal trends and variability in indices of perinatal outcomes

Accurate estimation of gestational age early in pregnancy is paramount for obstetric care decisions and for determining fetal growth and other conditions that may necessitate timing the iatrogenic intervention or delivery. We sought to examine temporal changes in the distributions of two measures of gestational age, namely, those based on menstrual dating and a clinical estimate. We further sought to evaluate relative comparisons and variability in indices of perinatal outcomes. We utilised the Natality data files in the US, 1990-2002 comprising women that delivered a singleton livebirth between 22 and 44 weeks gestation (n = 42 689 603). Changes were shown in the distributions of gestational age based on menstrual vs. clinical estimate between 1990 and 2002, as well as changes in the proportions of preterm (<37, <32 and <28 weeks) and post-term (>or=42 weeks) birth, and small- (SGA; <10th percentile) and large-for-gestational-age (LGA; birthweight >90th percentile) births. While the absolute rates of preterm birth <37 weeks, SGA and LGA births were lower based on the clinical estimate of gestational age relative to that based on menstrual dating, the increases in preterm birth rate between 1990 and 2002 were fairly similar between the two measures of gestational dating. However, the decline in post-term births was larger, based on the clinical estimate (-73.8%), than on the menstrual estimate (-36.6%) between 1990 and 2002. While the clinical estimate of gestational age appears to provide a reasonably good approximation to the menstrual estimate, disregarding the clinical estimate of gestational age may ignore the advantages of gestational age assessment in modern obstetrics.