Screening for the small-for-dates fetus: a two-stage ultrasonic examination schedule.

To find an effective routine screening method for small-for-dates fetuses 474 women with singleton pregnancies participated in a two-stage ultrasonic examination schedule. At the first-stage examination, which was conducted in early pregnancy, fetal crown-rump length or biparietal diameter was measured for an accurate assessment of gestational age, which was essential for interpreting the results of the second-stage examination. The second-stage examination was performed at 34-36 weeks and entailed measuring seven fetal variables, the results of which were assessed singly and in combination after delivery to identify the best indicator of small-for-dates fetuses. Fetal head measurements proved to be the least sensitive indicators of growth retardation, correctly identifying only 56-59% of cases. Measurements of trunk area and circumference, however, correctly identified 81% and 83% of cases respectively, but the most effective screening index was the product of crown-rump length and trunk area: with this index 34 out of 36 small-for-dates fetuses (94%) were correctly identified. Calculating the product of crown-rump length and trunk area from ultrasonic displays is quick and simple, and combined with the first-stage examination is a highly reliable screening method for small-for-dates fetuses.     

Screening for fetal malformations using ultrasound and measurements of alpha-fetoprotein in maternal serum.

Fetal ultrasound combined with semiquantitative measurements of alpha-fetoprotein in maternal serum was used for early detection of neural tube defects and omphalocele in 10 147 pregnancies. The accurate assessment of gestational age, obtained by ultrasound, facilitated evaluation of alpha-fetoprotein concentrations in selecting cases for amniocentesis. The advantage of screening with two independent methods is suggested by the finding that eight out of 10 cases with malformations (spina bifida, encephalocele, anencephalus, omphalocele) were detected when both methods were used. Screening by routine ultrasound alone detected only four malformations and by measurement of alpha-fetoprotein alone only seven. The results suggest that, in a low risk population, ultrasound should be combined with the measurement of alpha-fetoprotein in screening for neural tube defects. Measurement of alpha-fetoprotein is indispensable in detection of the small neural tube defects, where the fetus would survive with severe sequelae. The semi-quantitative analysis of alpha-fetoprotein that may be used in combination with ultrasound examination is of negligible cost.     

Risk assessment adjusted for gestational age in maternal serum screening for Down's syndrome.

OBJECTIVE--To investigate the relation between errors in calculation of gestational age and assessment of risk of Down''s syndrome and to analyse the implications for screening programmes. DESIGN--Retrospective analysis of dating of gestational age by menstrual history v ultrasound scan. Computer program with maternal age and concentrations of alpha fetoprotein and free beta human chorionic gonadotrophin to calculate risk for a range of expected dates of delivery. Computer simulated prospective application of new screening programme. SETTING--Teaching hospitals in Nottingham. SUBJECTS--31,561 women with singleton pregnancies with gestational age based on routine ultrasound scan. Computer simulation of 20,000 women in three age ranges (up to 37; up to 40; all). MAIN OUTCOME MEASURES--Distribution of error between gestational age based on ultrasound scan v menstrual history. Proportion of women in the population who require precise dating of pregnancy; proportion of women who require amniocentesis. RESULTS--With gestational age derived from ultrasound scan as reference the 95% confidence interval for gestational age by menstrual history was -27 to +9 days. A screening programme for Down''s syndrome for women up to age 40 would yield a low risk (< 1:250) for this range of days in 86.0% of cases. The 14.0% of women remaining would have one or more high risk values in their report and would thus require an ultrasound scan for precise dating of the pregnancy; 30% of these--that is, 3.7% of the screened population--would be identified as high risk and require consideration for amniocentesis. CONCLUSIONS--Screening programmes for Down''s syndrome require the facility for precise dating of pregnancy to improve the accuracy of risk assessment. This can be achieved without introducing additional scans for early dating in the whole population but by selecting only those cases (about 14%) when an error in dates is likely to affect the risk of Down''s syndrome.     

The rate of early fetal growth in the human subject

Data from 354 embryos and fetuses between 20 and 200 mm crown rump length obtained by therapeutic abortion in 3 different countries were evaluated. All Danich and Hungarian and the majority of American specimens were measured immeditely after delivery in the fresh condition. In the mathematical evaluation linear regressions were calculated by the method of least squares for arbitrarily defined ranges to 20-50 mm and 50-200 mm crown rump lenghts. The material was analyzed statistically so that confidence limits could be drawn for the estimation of gestational age from crown rump length measurements. All data in the 20-50 mm range were combined, but beyond that fetal length the statistics for the Hungarian group were calculated separatley. The equation calculated to fit the data in the 20-50 mm rage is A = 46 + 0.71 L where A is gestational age in days and L is crown rump lenght in mm. The 95% confidence limits of regression are 0.57-0.83 days/mm and the correlation between gestational age and crown rump length is 0.65. Estimates of gestational age from sitting height measurements can be made + or - 15 days with 95% confidence. The equation for the combined Danish and American data in the range 50-200 mm is A = 64 + 0.41 L. The 95% confidence limits for the regression are 0.36-0.46 days mm and the correlation between gestational age and crown rump length is 0.70. Estimates of gestational age from crown rump length can be made + or - 26 days with 95% confidence. The data from the Hungarian study in the 50-200 mm sitting height range differ from those of the combined Danish and American material. The regression of days/mm (0.22) was significantly less at p. 01 level supporting the suspected bias in the Hungarian material, but the correlation between gestational age and crown rump length, 0.62, was not significantly less than that of the combined Danish and American data. Thus, if the difference in the slope was due to a bias, the bias was relatively consistent from patient to patient. Comparison of the results with those of Streeter (1920, 1951) indicates that the considerable discrepancy at the embryonic stages diminishes gradually in the fetal period and eventually becomes quite insignificant.     

Estimation of gestational age in Egyptian native goats by ultrasonographic fetometry

The main aim of the present study was to estimate the gestational age of Egyptian goats by B-mode ultrasound measurement of embryonic or fetal parts throughout pregnancy. Trans-rectal (TR) ultrasonography (7 MHz) was carried out on 15 pregnant Egyptian does at Day 10 post mating on alternate days until Day 25 and then once at 3-5-day intervals until Day 50. Trans-abdominal (TA) ultrasonography (3.5-5 MHz) was carried out on the same animals from Days 25 to 130 at 3-5-day intervals. After imaging the embryo or the fetus, the following parameters were measured: length of the embryo or fetus (CRL), heart rate (FHR), biparital diameter (BPD), trunk diameter (TD), placentome size (PS), umbilical cord diameter (UCD) and femur length (FL). The average of days at which the embryonic vesicle was first determined by TR and TA ultrasonography was 16.98+/-1.97 and 27.87+/-3.48, respectively. The embryo proper with a beating heart was first determined by TR and TA ultrasonography at an average of 22.36+/-2.66 and 30.36+/-4.75 days, respectively. All the fetal measures were significantly (P<0.0001) correlated with the gestational age. With the exception of fetal heart rate (R(2)=0.551), all the measured fetal structures were highly correlated (R(2)> or =90) with the gestational age. In conclusion, the age of embryo or fetus in Egyptian does can be estimated by ultrasound measuring the crown rump length, biparital diameter, trunk diameter, placentome size, umbilical cord diameter and femur length.     

Determination of fetal age by ultrasonography in St. Kitts green monkeys

Ultrasound assessments of fetal growth have been used in other species of primates to estimate fetal age, but there are no published morphometrics for the St. Kitts green monkey (Chlorocebus sabaeus), a species that has been important for studies of transplantation of fetal tissue into the brain as potential treatment for degenerative disease. Previous studies with other primate species have used relatively small numbers of pregnancies, measured repeatedly, to derive regressions for predicting fetal age from ultrasound studies. The present study derives data from 967 pregnancies, collected over a 9-year period, for predicting fetal age from ultrasound measurements of crown rump length, biparietal diameter, head circumference, abdominal circumference, and femur length in the St. Kitts green monkey. Linear and polynomial regressions were determined from pregnancies dated from a 3- to 4-day breeding period and confirmed in a second, independent group of pregnant monkeys with more extended breeding times to determine their accuracy for predicting fetal age. Although similar to morphometrics reported in other monkey species, there were some significant differences. These data will improve the estimates of fetal ages in previously published studies of St. Kitts green monkeys and provide more precise estimates of fetal age in studies of fetal development, genomics, and reproductive toxicology.     

Screening for Down's syndrome based on individual risk.

OBJECTIVE--To evaluate the effectiveness of biochemical screening of individual pregnancies for Down''s syndrome risk. DESIGN--Retrospective determination of risk. SETTING--Obstetric and cytogenetic services in Tayside, Scotland. SUBJECTS--3436 pregnant women who had screening for neural tube defects in the second trimester during November 1988 to March 1990 and whose pregnancies were dated by ultrasonography. Three women with pregnancies associated with Down''s syndrome reported later in 1990. MAIN OUTCOME MEASURES--Individual risk calculated from age at estimated date of delivery; chorionic gonadotrophin and alpha fetoprotein concentrations in serum samples obtained at precisely determined gestational ages in second trimester. Results of karyotype determination and outcome of pregnancy. RESULTS--During November 1988 to March 1990 karyotypes were determined for 5% of pregnancies for reasons of maternal age and genetic history and one of the eight affected fetuses was detected. Individual risk could not be calculated for 347 pregnancies, but screening on this basis would have detected five of the cases and required screening in 194 out of 3089 (6.3%) pregnancies; all three affected pregnancies reported later in 1990 would also have been detected, giving a success rate of 73% (95% confidence interval 39% to 94%). The age distribution of women according to individual risk suggests that women over 35 would be screened effectively. CONCLUSION--Screening based on individual risk would use resources more effectively than screening based on maternal age and genetic history without affecting detection rates in older women.     

超声系统筛查在孕早期胎儿中枢神经系统先天畸形诊断的价值分析

目的:探讨超声系统筛查在孕早期胎儿中枢神经系统先天畸形诊断的价值分析。方法:选取2014年3月~2017年4月来我院超声科行孕早期胎儿颈部透明层(Nuchal translucency,NT)筛查的孕妇2084例,胎儿共2135例。采用超声测量胎儿头臀长(Croen rump length,CRL)和颈部透明层(Nuchal translucency,NT)值,通过头胸部正中矢状断面、侧脑室水平横断面、小脑及后颅窝池断面、脊柱长轴断面等4个超声影像标准断面对孕早期胎儿的中枢神经系统解剖结构进行系统检查,统计各组在上述4个超声标准断面的检查显示情况及NT值,同时分析NT值、标准断面显示率与孕龄的关系,统计分析孕早期应用超声影像标准断面检查对中枢神经系统畸形的检出率、诊断敏感度、特异度、阳性预测值、阴性预测值。结果:孕早期胎儿采用超声检查,结果显示头胸部正中矢状断面、侧脑室水平横断面、小脑及后颅窝池断面、脊柱长轴断面的超声影像学显示率分别为98.17%、99.44%、98.78%和98.97%,不同孕龄组间超声断面显示率差异对比,x~2检验值分别为0.25、1.65、0.62、0.13,差异无统计学意义(P0.05);孕早期超声诊断胎儿中枢神经系统畸形的敏感度为90.91%,特异度为100%,阳性预测值为100%,阴性预测值为99.48%;正常胎儿的NT值与其孕龄呈正相关(r=0.153)。结论:超声检查对孕早期胎儿中枢神经系统结构畸形的显示率较高,且不受胎儿孕龄影响。     

Screening for Down's syndrome using serum alpha fetoprotein: a retrospective study indicating caution.

A report was made on the outcome of a four year retrospective study in 27 064 pregnancies, of the clinical efficiency, sensitivity, and specificity of a screening programme for Down''s syndrome based on reported strategies related to the measurement of maternal serum alpha fetoprotein. This study identified 27 pregnancies affected by Down''s syndrome with a median multiple of the median maternal serum alpha fetoprotein concentration of 0.82. This figure is considerably higher than that obtained from previous reports on this subject. With an age related multiple of the median maternal serum alpha fetoprotein strategy, 30.8% of Down''s affected pregnancies were identified as well as 11.6% of unaffected pregnancies. Perhaps a United Kingdom collaborative study should begin to investigate the reasons for such wide population variance in the reports for the median multiple of the median for Down''s affected pregnancies. Until such studies are carried out, screening for Down''s syndrome based on low maternal serum alpha fetoprotein concentration is premature.     

A randomised controlled trial comparing two schedules of antenatal visits: the antenatal care project.

OBJECTIVE--To compare the clinical and psychological effectiveness of the traditional British antenatal visit schedule (traditional care) with a reduced schedule of visits (new style care) for low risk women, together with maternal and professional satisfaction with care. DESIGN--Randomised controlled trial. SETTING--Places in south east London providing antenatal care for women receiving shared care and planning to deliver in one of three hospitals or at home. SUBJECT--2794 women at low risk fulfilling the trial''s inclusion criteria between June 1993 and July 1994. MAIN OUTCOME MEASURES--Measures of fetal and maternal morbidity, health service use, psychosocial outcomes, and maternal and professional satisfaction. RESULTS--Pregnant women allocated to new style care had fewer day admissions (0.8 v 1.0; P=0.002) and ultrasound scans (1.6 v 1.7; P=0.003) and were less often suspected of carrying fetuses that were small for gestational age (odds ratio 0.73; 95% confidence interval 0.54 to 0.99). They also had some poorer psychosocial outcomes; for example, they were more worried about fetal wellbeing antenatally and coping with the baby postnatally, and they had more negative attitudes to their babies, both in pregnancy and postnatally. These women were also more dissatisfied with the number of visits they received (odds ratio 2.50; 2.00 to 3.11). CONCLUSIONS--Patterns of antenatal care involving fewer routine visits for women at low risk may lead to reduced psychosocial effectiveness and dissatisfaction with frequency of visits. The number of antenatal day admissions and ultrasound scans performed may also be reduced. For the variables reported, the visit schedules studied are similar in their clinical effectiveness. Uncertainty remains as to the clinical effectiveness of reduced visit schedules for rare pregnancy problems.     

How healthy are clones and their progeny: 5 years of field experience

There is considerable concern regarding the health of cloned cattle and their safety as a source of food. The objective was to summarize 5 years of commercial experience with cloning in three countries (United States, Argentina and Brazil). Overall, only 9% of transferred embryos resulted in calves; efficiency ranged from 0 to 45% (most were from 1 to 10%, but 24% of cell lines never produced live calves). There was no significant difference in pregnancy rate following transfer of one versus two embryos. Before 90 days of gestation, two ultrasound markers for embryo death were found, either crown rump length (CRL) or heart beat less than 7.5mm and 150bpm, respectively, were observed alone or together in 27% of clones that died. In addition, after 100 days of pregnancy, placental edema, hydrops fetalis and increased abdominal circumference size were used as ultrasound findings of a fetus at risk of loss. At 114 days of gestation, abdominal circumference in clones that died was statistically larger than in clones that survived alive to term and from MOET- and IVF-derived pregnancies (P<0.05). Since elective cesarean section (C-section) was partially replaced by natural or assisted parturition, C-section rates decreased from 100% in 2000 to 54% in 2005. On average, 42% of cloned calves died between delivery and 150 days of life; the most common abnormalities were: enlarged umbilical cord (37%), respiratory problems (19%), calves depressed/prolonged recumbency (20%) and contracted flexor tendons (21%). From 11 blood parameters evaluated during the first week of life, lactate decreased twice and glucose doubled its original value from 24h to 7 days. Adult cloned females had normal breeding and calving rates and cloned bulls produced good quality semen and had normal fertility when used for AI or natural mating. In conclusion, cloning had no risks qualitatively different from those encountered in animals involved in modern agricultural practices, although the frequency of the risks appeared to be increased in cattle during the early portions of the life cycle of cattle clones.     

Prenatal ionizing irradiaton and early postnatal growth of Colombian and Bolivian squirrel monkeys (Saimiri sciureus)

Fetal squirrel monkeys of Bolivian and Colombian origin were exposed to 100 rad cobalt-60 radiation in utero and carried to term by the dams. Body weight, head circumference, crown–rump length, and food intake were measured during the first 28 postnatal days. Significant subspecies differences were noted in both mothers and offspring, the Colombian squirrel monkeys being generally larger than the Bolivians. The irradiated offspring weighed significantly less, had significantly smaller crania, and consumed significantly less food than control animals. A statistically nonsignificant decrement was also evident in the crown–rump length of radiation-treated infants.     

Antenatal maternal serum screening for Down's syndrome: results of a demonstration project.

OBJECTIVES--To assess the implementation of antenatal screening for Down''s syndrome in practice, using individual risk estimates based on maternal age and the three serum markers: alpha fetoprotein, unconjugated oestriol, and human chorionic gonadotrophin. DESIGN--Demonstration project of Down''s syndrome screening; women with a risk estimate at term of 1 in 250 or greater were classified as "screen positive" and offered diagnostic amniocentesis. SETTING--Hospital and community antenatal clinics in four health districts in London. SUBJECTS--12,603 women of all ages with singleton pregnancies seen between February 1989 and the end of May 1991, with follow up of the outcome of pregnancy completed to the end of 1991. MAIN OUTCOME MEASURES--Uptake of screening, detection rate for Down''s syndrome, false positive rate, odds of being affected given a positive result, and uptake of amniocentesis in women with positive screening results, together with the costs of the screening programme. RESULTS--The uptake of screening was 74%. The detection rate was 48% (12/25), and the false positive rate was 4.1%, consistent with results expected from previous work based on observational studies. There was a loss of detection due to the selective use of ultrasound scans among women with positive screening results. One affected pregnancy occurred among 205 reclassified as negative; this illustrated the danger of false negatives occurring in this group and lends weight to the view that if an ultrasound estimate of gestational age is used it should be carried out routinely on all women rather than selectively among those with positive results. The estimated cost of avoiding the birth of a baby with Down''s syndrome was about 38,000 pounds, substantially less than the lifetime costs of care. CONCLUSION--Antenatal maternal serum screening for Down''s syndrome is effective in practice and can be readily integrated into routine antenatal care. It is cost effective and performs better than selection for amniocentesis on the basis of maternal age alone.     

Chromosomal microarray analysis for pregnancies with abnormal maternal serum screening who undergo invasive prenatal testing

Recently, chromosomal microarray analysis (CMA) has been implemented as a first-tier test in pregnancies with ultrasound anomalies. However, its application for pregnancies with abnormal maternal serum screening (AMSS) only is not widespread. This study evaluated the value of CMA compared to traditional karyotyping in pregnancies with increased risk following first- or second-trimester maternal serum screening. Data from 3973 pregnancies with referral for invasive prenatal testing following AMSS were obtained from April 2016 to May 2020. Routine karyotyping was performed and single nucleotide polymorphism array was recommended. The foetuses were categorized according to the indications as AMSS only (group A) and AMSS with ultrasound anomalies (group B). CMA was performed on 713 prenatal samples. The proportion of women opting for CMA testing in both groups increased over the years. The incremental yield of clinically significant findings for pregnancies with high risk of screening results was similar to that for the foetuses with ultrasound soft markers (P > 0.05), but significantly lower than that for the foetuses with structural anomalies (P < 0.05). The total frequencies of variants of unknown significance in groups A and B showed no significant difference (P > 0.05). CMA should be performed for pregnant women undergoing prenatal invasive testing due to AMSS, especially with high-risk results, regardless of ultrasound findings.     

Body Proportions of the Infant

Growth is usually evaluated by single measurements which reflect only that direction of growth. At birth the relationship between measurements is often considered as Rohrer's Ponderal Index which describes weight in relation to length but can be misleading especially when considering premature infants. We propose that it is more appropriate to study the relationship of different anthropometric measurements to define normality and thereby create limits from which abnormalities in growth may be diagnosed. Weight, crown heel length, crown rump length and head circumference were measured in 305 healthy infants, at 26–42 gestational weeks to obtain reference values. Subischial leg length was calculated. A multivariate model was made which could be useful to distinguish the form and shape of an infant and to identify abnormalities in growth.     

Maternal serum screening for Down's syndrome in early pregnancy.

The possibility of improving the effectiveness of antenatal screening for Down''s syndrome by measuring human chorionic gonadotrophin concentrations in maternal serum during the second trimester to select women for diagnostic amniocentesis was examined. The median maternal serum human chorionic gonadotrophin concentration in 77 pregnancies associated with Down''s syndrome was twice the median concentration in 385 unaffected pregnancies matched for maternal age, gestational age, and duration of storage of the serum sample. Measuring human chorionic gonadotrophin in maternal serum was an effective screening test, giving a lower false positive rate (3%) at a 30% detection rate than that for maternal age (5%) and the two existing serum screening tests, unconjugated oestriol (7%) and alpha fetoprotein (11%). The most effective screening results were obtained with all four variables combined; at the same 30% detection rate the false positive rate declined to 0.5%. The new screening method would detect over 60% of affected pregnancies, more than double that achievable with the same amniocentesis rate in existing programmes (5%), and could reduce the number of children born with Down''s syndrome in the United Kingdom from about 900 a year to about 350 a year.     

Randomised controlled trial of aspirin and aspirin plus heparin in pregnant women with recurrent miscarriage associated with phospholipid antibodies (or antiphospholipid antibodies)

OBJECTIVE: To determine whether treatment with low dose aspirin and heparin leads to a higher rate of live births than that achieved with low dose aspirin alone in women with a history of recurrent miscarriage associated with phospholipid antibodies (or antiphospholipid antibodies), lupus anticoagulant, and cardiolipin antibodies (or anticardiolipin antibodies). DESIGN: Randomised controlled trial. SETTING: Specialist clinic for recurrent miscarriages. SUBJECTS: 90 women (median age 33 (range 22-43)) with a history of recurrent miscarriage (median number 4 (range 3-15)) and persistently positive results for phospholipid antibodies. INTERVENTION: Either low dose aspirin (75 mg daily) or low dose aspirin and 5000 U of unfractionated heparin subcutaneously 12 hourly. All women started treatment with low dose aspirin when they had a positive urine pregnancy test. Women were randomly allocated an intervention when fetal heart activity was seen on ultrasonography. Treatment was stopped at the time of miscarriage or at 34 weeks'' gestation. MAIN OUTCOME MEASURES: Rate of live births with the two treatments. RESULTS: There was no significant difference in the two groups in age or the number and gestation of previous miscarriages. The rate of live births with low dose aspirin and heparin was 71% (32/45 pregnancies) and 42% (19/45 pregnancies) with low dose aspirin alone (odds ratio 3.37 (95% confidence interval 1.40 to 8.10)). More than 90% of miscarriages occurred in the first trimester. There was no difference in outcome between the two treatments in pregnancies that advanced beyond 13 weeks'' gestation. Twelve of the 51 successful pregnancies (24%) were delivered before 37 weeks'' gestation. Women randomly allocated aspirin and heparin had a median decrease in lumbar spine bone density of 5.4% (range -8.6% to 1.7%). CONCLUSION: Treatment with aspirin and heparin leads to a significantly higher rate of live births in women with a history of recurrent miscarriage associated with phospholipid antibodies than that achieved with aspirin alone.     

辽东栎林内不同小生境下幼树植冠构型分析

以黄土高原黄龙山林区辽东栎林内3个小生境（林下、林隙、林缘）下辽东栎天然更新幼树为研究对象,采用典型抽样法对辽东栎幼树侧枝、叶片和树冠的空间分布状况以及生物量分配状况进行调查分析,探讨微生境与幼树植冠构型特征的关系,明确辽东栎幼树对不同小生境的适应策略,为栎林经营和林分结构优化提供理论依据。结果显示：（1）3种生境下辽东栎幼树构型发生了可塑性变化,林下幼树树冠层次比较单一,林隙与林缘的幼树树冠层次更加丰富。（2）由林下至林缘,幼树的树高、枝下高呈逐渐减小的趋势,而地径变化趋势与之相反;幼树的冠幅、树冠面积、树冠率呈先增加后减小的趋势,并且林下与林隙、林缘的差异显著;幼树的总体分枝率、逐步分枝率、枝径比呈先增加后减小的趋势。（3）3种生境下,幼树的一级枝的枝长、直径与倾角随着树高的增加而呈减小的趋势,但3种生境的差异不显著;林下一级枝主要分布在冠层中上部,而林隙与林缘一级枝主要分布在冠层中下、中上部。（4）由林下至林缘幼树叶长、叶宽、单叶面积和比叶面积逐渐降低,而单株叶数、叶总面积、叶面积指数呈先增大后减小趋势;与其他2种生境相比林下叶片分布趋于冠层上部。（5）幼树地上部分生物量中林下主干生物量占83%,枝和叶生物量只占17%;而林隙与林缘虽然各部位生物量有所差异但比例基本一致,其中主干占66%左右,枝和叶生物量占34%左右。研究表明,林隙生境下幼树的构型优于林缘和林下生境,在今后栎林的经营中,可以通过适当间伐来增加林隙数量,为森林更新和结构的优化提供有利条件。     

Growth and development of the Tasmanian devil (Sarcophilus harrisii) at Healesville Sanctuary,Victoria, Australia

A study of the growth and development of the Tasmanian devil (Sarcophilus harrisii) was undertaken on a litter born at Healesville Sanctuary in Healesville, Victoria, Australia. Measurements of crown–rump length, head length, and head width were recorded every week from birth. Body weight was recorded weekly once the joeys were detached from the teat at 142 days of age, until 218 days of age. The growth curves revealed an initial linear increase in crown–rump lengths until approximately 60 days of age, when the gradient increased, while head length and head width showed a largely linear increase with age. The appearances of various morphological characteristics were also recorded. Zoo Biol 22:497–505, 2003. © 2003 Wiley‐Liss, Inc.     

Quantification of overdiagnosis in randomised trials of cancer screening: an overview and re-analysis of systematic reviews

The degree of overdiagnosis in common cancer screening trials is uncertain due to inadequate design of trials, varying definition and methods used to estimate overdiagnosis. Therefore, we aimed to quantify the risk of overdiagnosis for the most widely implemented cancer screening programmes and assess the implications of design limitations and biases in cancer screening trials on the estimates of overdiagnosis by conducting an overview and re-analysis of systematic reviews of cancer screening. We searched PubMed and the Cochrane Library from their inception dates to November 29, 2021. Eligible studies included systematic reviews of randomised trials comparing cancer screening interventions to no screening, which reported cancer incidence for both trial arms. We extracted data on study characteristics, cancer incidence and assessed the risk of bias using the Cochrane Collaboration’s risk of bias tool. We included 19 trials described in 30 articles for review, reporting results for the following types of screening: mammography for breast cancer, chest X-ray or low-dose CT for lung cancer, alpha-foetoprotein and ultrasound for liver cancer, digital rectal examination, prostate-specific antigen, and transrectal ultrasound for prostate cancer, and CA-125 test and/or ultrasound for ovarian cancer. No trials on screening for melanoma were eligible. Only one trial (5%) had low risk in all bias domains, leading to a post-hoc meta-analysis, excluding trials with high risk of bias in critical domains, finding the extent of overdiagnosis ranged from 17% to 38% across cancer screening programmes. We conclude that there is a significant risk of overdiagnosis in the included randomised trials on cancer screening. We found that trials were generally not designed to estimate overdiagnosis and many trials had high risk of biases that may draw the estimates of overdiagnosis towards the null. In effect, the true extent of overdiagnosis due to cancer screening is likely underestimated.