Bacterial communities of the threatened Western Pond Turtle may be impacted by land use.

As semi-aquatic species that use both terrestrial and aquatic habitats, freshwater turtles and their microbial communities are especially sensitive to the impacts of habitat disturbance. In this study, we use 16S rRNA amplicon sequencing to characterize the shell and cloacal bacterial communities of turtles in the San Francisco Bay Area. We captured western pond turtles (Actinemys/Emys marmorata) across eight sites located in urban and rural environments, along with invasive red-eared sliders (Trachemys scripta elegans). We assessed differences in western pond turtle bacterial communities diversity/composition between shell and cloacal samples and evaluated how alpha/beta diversity metrics were influenced by habitat quality. We found phylum-level bacterial taxonomic turnover in the bacterial communities of western pond turtles relative to the host tissue substrate samples. Our findings indicate that location identity elicits a high degree of lower-level (i.e. species/genus) bacterial taxonomic turnover. Further, we found that samples originating from good quality habitat had poorer shell bacterial communities but more diverse cloacal ones. The shell bacterial communities of red-eared sliders overlapped with those western pond turtles suggesting the existence of microbial dispersal between these two species. Our results add to our current understanding of turtle symbiont microbial ecology by establishing patterns of bacterial symbiont variation in an urban to rural gradient.

Selection of Standards for Sonographic Fetal Femur Length by Use of z-scores.

OBJECTIVES: This study aimed to evaluate which of four established norms should be used for sonographic assessment of fetal femur length (FL). STUDY DESIGN: Cross-sectional study using pooled data from four maternal-fetal medicine practices. Inclusion criteria were singleton fetus, gestational age (GA) 220/7 to 396/7 weeks, biometry measured, and fetal cardiac activity present. Four norms of FL were studied: Hadlock et al, the INTERGROWTH-21st Project (IG-21st), the World Health Organization Fetal Growth Curves (WHO), and the National Institutes of Child Health and Human Development Fetal Growth Studies, unified standard (NICHD-U). The fit of our FL measurements to each norm was assessed by these criteria: mean z-score close to 0, standard deviation (SD) of z close to 1, Kolmogorov-Smirnov D-statistic close to zero, Youden J-statistic close to 1, approximately 5% of exams <5th percentile, and approximately 5% of exams >95th percentile. RESULTS: In 26,177 ultrasound exams, our FL measurements had the best fit to the WHO standard (mean z-score 0.15, SD of z 1.02, D-statistic <0.01, J-statistic 0.95, 3.4% of exams <5th percentile, 7.0% of exams >95th percentile). The mean of the IG-21st standard was smaller than the other norms and smaller than our measurements, resulting in underdiagnosis of short FL. The mean of the Hadlock reference was larger than the other norms and larger than our measurements, resulting in overdiagnosis of short FL. The SD of the NICHD-U standard was larger than the other norms and larger than our observations, resulting in underdiagnosis of both short and long FL. Restricting the analysis to a subgroup of 7,144 low-risk patients without risk factors for large- or small-for- GA produced similar results. CONCLUSION: Of the norms studied, the WHO standard is likely best for diagnosis of abnormal FL. KEY POINTS: · There are >30 norms for fetal FL.. · It is unknown which norm should be used.. · Our data fit the World Health Organization standard better than the other norms..

Choice of standards for sonographic fetal abdominal circumference percentile.

BACKGROUND: The diagnosis of abnormal fetal abdominal circumference is based on values >90th or <10th percentile. There are dozens of established norms that can be used to determine the percentile of a given abdominal circumference measurement, but there is no established method to determine which norms should be used. OBJECTIVE: This study aimed to evaluate the applicability of 5 established abdominal circumference norms to our measurements and to determine which, if any, should be used for the diagnosis of abnormal fetal abdominal circumference. STUDY DESIGN: Data were pooled from 6 maternal-fetal medicine practices to conduct a cross-sectional study. The inclusion criteria were a singleton fetus at 22.0 to 39.9 weeks of gestation with cardiac activity present, complete fetal biometry measured, and examination from 2019 or 2020. For patients with >1 eligible examination during the study period, a single examination was chosen at random for inclusion. Five norms of abdominal circumference were studied: the Hadlock formula, the World Health Organization Fetal Growth Curves, the International Fetal and Newborn Growth Consortium for the 21st-Century Project; and the National Institutes of Child Health and Human Development Fetal Growth Studies (fetuses of White patients and unified standard). Using formulas relating abdominal circumference to gestational age, we calculated the z scores of abdominal circumference (standard deviations from the mean), standard deviation of the z score, Kolmogorov-Smirnov D statistic, and relative mean squared error. The 5 norms were assessed for fit to our data based on 6 criteria: mean z score close to 0, standard deviation of the z score close to 1, low D statistic, low mean squared error, fraction of values >90th percentile close to 10%, and fraction of values <10th percentile close to 10%. RESULTS: The inclusion criteria were met in 40,684 ultrasound examinations in 15,042 patients. Considering the 6 evaluation criteria, observed abdominal circumferences had the best fit to the World Health Organization standard (mean z score of 0.11±1.05, D statistic of 0.041, mean squared error of 0.84±1.46, 13% of examinations >90th percentile, and 7% of examinations <10th percentile). The Hadlock reference had an anomaly in its assumption of a constant standard deviation, resulting in the underdiagnosis of abnormal values at early gestational ages and overdiagnosis at late gestational ages. The International Fetal and Newborn Growth Consortium for the 21st-Century Project standard had a mean circumference smaller than all the other norms, resulting in the underdiagnosis of small circumferences and the overdiagnosis of large circumferences. Similar results were observed when restricting the analyses to a low-risk subgroup of 5487 examinations without identified risk factors for large for gestational age or small for gestational age. CONCLUSION: The diagnosis of abnormal abdominal circumference depends on the norms used to define abdominal circumference percentiles. The World Health Organization standard had the best fit for our data.

Impact of adding abdominal circumference to the definition of fetal growth restriction.

BACKGROUND: Fetal growth restriction has traditionally been defined as fetuses with an estimated fetal weight <10th percentile for gestational age. In 2020, the Society for Maternal-Fetal Medicine recommended that the definition be expanded to include either an estimated fetal weight<10th percentile or a fetal abdominal circumference<10th percentile. OBJECTIVE: We sought to determine the impact of adding the criterion abdominal circumference<10th percentile on the rate of diagnosis of fetal growth restriction vs using the criterion estimated fetal weight<10th percentile alone. In addition, we evaluated the definition proposed by Copel and Bahtiyar, estimated fetal weight<10th percentile or abdominal circumference<5th percentile. STUDY DESIGN: This was a retrospective, descriptive study from 3 consultative maternal-fetal medicine practices. Biometry was compiled from ultrasound examinations from January 2019 to July 2020. The inclusion criteria were singleton pregnancy, gestational age of ≥24 weeks, presence of fetal cardiac activity, and presence of 4 standard fetal biometry parameters (biparietal diameter, head circumference, abdominal circumference, and femur length). We tabulated the indications for the examinations and the number of examinations meeting several criteria for the diagnosis of fetal growth restriction: Traditional criterion (estimated fetal weight<10th percentile), Copel-Bahtiyar criteria (estimated fetal weight<10th percentile or abdominal circumference<5th percentile), and Society for Maternal-Fetal Medicine criteria (estimated fetal weight<10th percentile or abdominal circumference<10th percentile). RESULTS: During the study period, 20,633 ultrasound examinations met the inclusion criteria. In 62% of examinations, there was ≥1 factor for fetal growth restriction, and in 51% of examinations, there was ≥1 factor for large for gestational age. The rate of estimated fetal weight<10th percentile was 9.7%. The rate of abdominal circumference<5th percentile was 5.7%, and the rate of abdominal circumference<10th percentile was 9.2%. The rate of fetal growth restriction was 9.7% using the traditional definition (estimated fetal weight<10th percentile only). The rate of fetal growth restriction was 10.2% using the Copel-Bahtiyar definition (estimated fetal weight<10th percentile or abdominal circumference<5th percentile), significantly higher than using the traditional definition (P<.001). The rate of fetal growth restriction was 11.6% using the Society for Maternal-Fetal Medicine definition (estimated fetal weight<10th percentile or abdominal circumference<10th percentile), significantly higher than using either the traditional or Copel-Bahtiyar definition (P<.001 for both). Among examinations with an abdominal circumference<10th percentile, 79% also had an estimated fetal weight<10th percentile and was considered fetal growth restriction even without considering abdominal circumference. CONCLUSION: Adding the criterion abdominal circumference<5th percentile or abdominal circumference<10th percentile to the definition of fetal growth restriction resulted in a statistically significant increase in the rate of diagnosis of fetal growth restriction. However, the absolute increase in the rate was small and was not expected to place a large burden on practice resources.