Understanding the different phases of fetal growth.

Fetal growth was studied in 78 newborns who had serial scans in pregnancy. Weight at birth correlated with growth in the first 2 trimesters but better with the growth between 28 and 32 weeks. The correlations for weight at growth cessation were better than those for weight at birth. Crown-heel length at cessation did not correlate with fetal growth in the first 2 trimesters. Maternal weight increase correlated with fetal weight and crown-heel length but not with head circumference at cessation. Maternal prepregnancy weight correlated with fetal growth between 28 and 32 weeks, but not with fetal growth in the second trimester. A negative correlation was found between estimated duration of growth cessation and relative head circumference at birth.     

Sex dimorphism in digital formulae of children

This paper presents results of a study designed to: 1) test for a sex difference in the relative lengths of the finger bones, including the second-to-fourth digit ratio (2D:4D), using left-hand radiographs taken in young children, 2) test whether sex differences can be explained by sex differences in fetal growth, and 3) test the serial stability of sex differences in relative digit lengths, including 2D:4D. Results are presented from 1,060 subjects of the California Child Health and Development Studies. One serial replication at about 9 years old is available from 271 subjects. Results indicate that relative digit lengths are sex-dimorphic in children (Manning et al. [1998] Hum. Reprod. 13:3000-3004, [2004] Early Hum. Dev. 80:161-168). Sex differences in digit length ratios are more pronounced within sibships, where shared family factors are controlled, and are not strongly associated with gross measures of fetal growth, like birth length or weight. Thus, sex differences in the fetal growth of the body are not implicated in sex differences in digital formulae, leaving open the possibility of more direct hormonal and/or genetic causation. However, 2D:4D declined between ages 6-8 in a longitudinal sample, and was a less consistent sex-dimorphic marker than 3D:4D across ethnic groups, suggesting that 3D:4D may be a better marker of perinatal sex differentiation. Prior conflicting findings about 2D:4D may be partly explained by variations in age and ethnicity of populations studied.     

Methodological challenges in the study of fetal growth

Several conceptual and methodological challenges must be solved in order to create knowledge that can be useful to pregnant women, their families, and any clinicians who serve them: (1) going beyond nominal and ordinal hypotheses and presenting estimates of conditional probabilities; (2) focusing on clearly defined outcomes; (3) modeling the relationship of fetal growth and length of gestation; (4) understanding the process of fetal growth even though most of our data is cross-sectional; (5) estimating the independent effects of genetics, race, ethnicity, maternal risk behaviors, medical prenatal care, and socioeconomic status on fetal growth and length of gestation; and (6) estimating the independent effects of maternal pre-pregnancy weight, weight gain during pregnancy, and nutrition on fetal growth and length of gestation. The analysis and writing of this study was funded, in part, by a grant from the National Institute of Child Health and Human Development (NICHD RO1 HD 20511). Troy D. Abell, Ph.D., M.P.H., is associate professor of anthropology and adjunct associate professor of family medicine at the University of Oklahoma. His major interests are in the biocultural determinants of fetal growth and the epistemologic issues inherent in statistical reasoning, scientific inference, and decision analysis.     

Fetal and placental traits at day 35 of pregnancy in relation to the estrogen receptor genotype in pigs

Fetuses from gilts with estrogen receptor (ESR) genotype AA (AA-AA and AA-AB) and BB (BB-AB and BB-BB) were compared at Day 35/36 of pregnancy, to examine whether fetal ESR genotype nested within maternal ESR genotype would affect fetal traits. Furthermore the relation of fetal body weight and fetal heart weight to various placental traits were evaluated relative to ESR genotype. Fetal and placental weight and length, and implantation surface area were not affected by fetal ESR genotype nested within maternal ESR genotype. Fetal weight was related similarly to placental length, placental weight, and implantation surface area: up to a certain threshold value (40 cm, 40 g and 250 cm2, respectively), an increase in the trait was associated with an increase of fetal weight. Thereafter, fetal weight did not change anymore. Thus, at Day 35/36 of pregnancy porcine fetuses seem to have a maximum growth potential. The percentage of AA-AA fetuses that had not reached this maximum growth potential was larger than of the other three genotype combinations studied, and therefore a higher subsequent fetal mortality may be expected in this group. Hearts of AA-AB fetuses were significantly heavier than those of BB-AB and BB-BB fetuses and tended to be heavier than those of AA-AA fetuses. The reason for this hypertrophy is unclear, but might be related to a difference in placental vascularity. Heart weight of fetuses from BB gilts increased with fetal weight, while heart weights of fetuses from AA gilts did not. Heart weight increased with an increase of placental length and implantation surface area up to 51 cm and 437 cm2, respectively, and thereafter decreased again. For BB-AB fetuses a similar relation was found between heart weight and placental weight, while heart weight of the other three genotype combinations remained unaffected as placental weight increased. The fetus and placenta are continuously changing during early pregnancy, therefore different mechanisms may change the demands for cardiac output. However, keeping in mind that placental size and blood volume are relatively large, placental vascularity and vascular development may play a major role. Therefore, further research on heart size, placental size and vascularity, relative to ESR genotype, is recommended.     

Normal development of fetuses resulting from Holstein semen processed for sex separation

Semen from two high fertility Holstein bulls with extensive histories in artificial insemination was specially processed for the purpose of sexing and then frozen. The semen was used to inseminate 200 open crossbred beef heifers carefully selected for reproductive soundness from a much larger group. Animals were inseminated alternately with the semen from one of the two bulls and subsequently slaughtered. There were 96 fetuses, ranging in age from 63 to 88 days, which were carefully examined for general appearance, fetal crown-rump length and body weight. There was no effect of sire on fetal size, but the difference between fetal sexes was significant, with the male fetus being appreciably heavier. The regression of fetal length on fetal age was linear and the regression of fetal weight on fetal age was curvilinear. Fetal age accounted for 92% to 96% of the variation in fetal weight and also in crown-rump length.     

Standards of morphological development in fetuses and newborns as a method of defining fetal age

Whenever the calendar age of the studied fetal material is not known we are bound to reconstruct it by replacing it with the developmental age. In this paper some common developmental standards used in the determination of fetal age are reviewed. The standards, as found in the relevant literature, are tested against a control group for their accuracy in predicting fetal age. The results indicate considerable discrepancy among the various standards. Further, the developmental ages defined by these standards often differ considerably from the known menstrual age. My own attempt to present a more reliable set of developmental standards is based on the analysis of three morphological features commonly used in biological assessment. Body weight, crown-heel length, and crown-rump length are measured in weekly termed groups representing the 20th-42nd weeks of intrauterine life. The accuracy of body weight and crown-heel length in predicting fetal age is tested both within and against a control group. Statistical analysis show no significant differences between the predicted and known fetal ages. These results indicate that body weight and crown-heel length are reliable developmental standards from which fetal age can be defined.     

Intrauterine growth of the guinea pig fetal-placental unit throughout pregnancy: regulation by utero-placental blood flow

The relationships between uterine blood flow (UBF) and growth related changes in guinea pig placental weight, fetal weight, and crown-rump (C-R) length were examined at 5-day intervals throughout pregnancy. Between days 5 and 20 (Day 0 = ovulation) of pregnancy, UBF reached peak levels that were related to increases in total uterine weight as a result of fetal-placental differentiation. Between days 20 and 40 of pregnancy, UBF remained at constant, basal levels while placental weight increased at a rate of approximately 500 mg per 5-day interval. During this time period, fetal weight and C-R length continued to increase, but at a less rapid rate. Between days 40 and 55 of pregnancy, a secondary elevation in UBF was observed that was temporally related to third trimester growth of the fetus (ie, weight and C-R length). Near term (day 65), UBF decreased and placental growth reached a plateau, whereas fetal weight and C-R length continued to increase. In order to determine the direct effects of UBF on regulating fetal-placental growth, mid-gestational (days 35-50) pregnant guinea pigs were subjected to UBF reduction and the growth parameters of the manipulated fetal-placental units were then examined at 2, 3, 4, and 10 days post-alteration and compared to controls. The reduction in UBF at hyperemic pregnancy sites to basal flow levels resulted in an abrupt curtailment of subsequent placental growth noticeable within 48 hr of the vascular reduction. Subsequently, fetal weight and crown-rump length parameters were depressed with respect to controls, but not until 4 and 10 days post-alteration, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessing the Causal Relationship of Maternal Height on Birth Size and Gestational Age at Birth: A Mendelian Randomization Analysis

Background

Observational epidemiological studies indicate that maternal height is associated with gestational age at birth and fetal growth measures (i.e., shorter mothers deliver infants at earlier gestational ages with lower birth weight and birth length). Different mechanisms have been postulated to explain these associations. This study aimed to investigate the casual relationships behind the strong association of maternal height with fetal growth measures (i.e., birth length and birth weight) and gestational age by a Mendelian randomization approach.

Methods and Findings

We conducted a Mendelian randomization analysis using phenotype and genome-wide single nucleotide polymorphism (SNP) data of 3,485 mother/infant pairs from birth cohorts collected from three Nordic countries (Finland, Denmark, and Norway). We constructed a genetic score based on 697 SNPs known to be associated with adult height to index maternal height. To avoid confounding due to genetic sharing between mother and infant, we inferred parental transmission of the height-associated SNPs and utilized the haplotype genetic score derived from nontransmitted alleles as a valid genetic instrument for maternal height. In observational analysis, maternal height was significantly associated with birth length (p = 6.31 × 10⁻⁹), birth weight (p = 2.19 × 10⁻¹⁵), and gestational age (p = 1.51 × 10⁻⁷). Our parental-specific haplotype score association analysis revealed that birth length and birth weight were significantly associated with the maternal transmitted haplotype score as well as the paternal transmitted haplotype score. Their association with the maternal nontransmitted haplotype score was far less significant, indicating a major fetal genetic influence on these fetal growth measures. In contrast, gestational age was significantly associated with the nontransmitted haplotype score (p = 0.0424) and demonstrated a significant (p = 0.0234) causal effect of every 1 cm increase in maternal height resulting in ~0.4 more gestational d. Limitations of this study include potential influences in causal inference by biological pleiotropy, assortative mating, and the nonrandom sampling of study subjects.

Conclusions

Our results demonstrate that the observed association between maternal height and fetal growth measures (i.e., birth length and birth weight) is mainly defined by fetal genetics. In contrast, the association between maternal height and gestational age is more likely to be causal. In addition, our approach that utilizes the genetic score derived from the nontransmitted maternal haplotype as a genetic instrument is a novel extension to the Mendelian randomization methodology in casual inference between parental phenotype (or exposure) and outcomes in offspring.     

光倒刺鲃的年龄与生长的初步研究

研究了光倒刺鲃(Spinibarbus hollandi)的年龄与生长规律,结果表明:光倒刺鲃鳞片年轮特征主要为疏密切割型。体长与鳞长呈直线相关L=44.44R-11.69,体重与体长呈指数函数相关W=0.0258L2.9125,4龄以前生长较快,生长指标高,体长指标高,体长和体重的相对增长率大,其生长规律可用Von Bertalanffy方程表达:Lt=67.3[1-e-0.2018(t-0.1338)],Wt=5441.44[1-e-0.2018(t-0.1338)]3。体重生长曲线的拐点位于t=5.678,拐点体长Lr=45.313cm,拐点体重Wr=1660.885g。光倒刺鲃雌性一般在3~4龄性成熟,雄鱼3龄时性成熟。     

Restriction of placental function alters heart development in the sheep fetus

Placental insufficiency, resulting in restriction of fetal substrate supply, is a major cause of intrauterine growth restriction (IUGR) and increased neonatal morbidity. Fetal adaptations to placental restriction maintain the growth of key organs, including the heart, but the impact of these adaptations on individual cardiomyocytes is unknown. Placental and hence fetal growth restriction was induced in fetal sheep by removing the majority of caruncles in the ewe before mating (placental restriction, PR). Vascular surgery was performed on 13 control and 11 PR fetuses at 110-125 days of gestation (term: 150 +/- 3 days). PR fetuses with a mean gestational Po(2) < 17 mmHg were defined as hypoxic. At postmortem (<135 or >135 days), fetal hearts were collected, and cardiomyocytes were isolated and fixed. Proliferating cardiomyocytes were counted by immunohistochemistry of Ki67 protein. Cardiomyocytes were stained with methylene blue to visualize the nuclei, and the proportion of mononucleated cells and length and width of cardiomyocytes were measured. PR resulted in chronic fetal hypoxia, IUGR, and elevated plasma cortisol concentrations. Although there was no difference in relative heart weights between control and PR fetuses, there was an increase in the proportion of mononucleated cardiomyocytes in PR fetuses. Whereas mononucleated and binucleated cardiomyocytes were smaller, the relative size of cardiomyocytes when expressed relative to heart weight was larger in PR compared with control fetuses. The increase in the relative proportion of mononucleated cardiomyocytes and the relative sparing of the growth of individual cardiomyocytes in the growth-restricted fetus are adaptations that may have long-term consequences for heart development in postnatal life.     

Sonographic biometrical normograms and estimation of fetal weight in the baboon (Papio anubis)

Background  In order to consider the non-human primate as an adequate model for studying prenatal diagnosis and therapy, comparative data on fetal growth should be available.
Methods  Sixty ultrasound scans were performed in 22 baboons between 14 and 167 days of gestation. Measurements included greatest length, head circumference, biparietal diameter (BPD), transcerebellar diameter, abdominal circumference (AC), femur length (FL), and amniotic fluid index. For all parameters growth curves were established and compared with human curves. In 18 animals, birth weight and placental weight were determined. Different equations described in the literature for estimating the human fetal weight were tested in the baboon.
Results  The fetal and placental growth pattern in the baboon was comparable with humans. The best predictor of fetal weight was the formula presented by Combs: 0.23966 × AC² × FL + 1.623 × BPD³.
Conclusions  A high similarity between baboon and human growth charts is shown. The best equation for estimating the baboon fetal weight is proposed.     

Effect of early fetal irradiation on the postnatal development of mouse.

BACKGROUND: An earlier study has shown that irradiation at the late fetal stage of Swiss albino mice disturbed postnatal growth and appearance of physiological markers. The present study was done to determine the effect of irradiation at the early fetal stage on the postnatal development of mouse. METHODS: Fourteen-day pregnant Swiss albino mice were exposed to 0.1-1.5 Gy of cobalt-60 gamma-rays. F1 pups were observed for < or = 6 weeks of age. Postnatal mortality, body weight and length, head length and width, tail length, and the time of appearance of physiological markers (pinna detachment, eye opening, fur development, vaginal opening and testes descent) were noted. RESULTS: There was no increase in congenital anomalies. Postnatal mortality and percentage of growth-retarded pups increased significantly at doses of 0.5-1.5 Gy. A significant delay in the appearance of all the physiological markers was also noted at these doses. Body length, head length, and tail length remained significantly lower than in the controls throughout the observation period at doses of 0.3-1.5 Gy, whereas body weight and head width showed such a persistent change only at > or = 0.5 Gy. CONCLUSIONS: The early fetal day 14 in mouse is sensitive to radiation-induced postnatal mortality and impairment of growth and temporal development of physiological markers, but not to induction of congenital anomalies. While mortality and physiological markers are not affected at <0.5 Gy, growth retardation appears to have a lower threshold of approximately 0.3 Gy.     

Prospective cohort study of factors influencing the relative weights of the placenta and the newborn infant.

OBJECTIVES: To determine the demographic, environmental, and medical factors that influence the relative weights of the newborn infant and the placenta and compare this ratio with other factors known to predispose to adult ill health. DESIGN: Prospective cohort study. SETTING: The tertiary referral centre for perinatal care in Perth, Western Australia. SUBJECTS: 2507 pregnant women who delivered a single live infant at term. MAIN OUTCOME MEASURES: Placental weight, birth weight, and the ratio of placental weight to birth weight. RESULTS: By multiple regression analysis the placental weight to birthweight ratio was significantly and positively associated with gestational age, female sex, Asian parentage, increasing maternal body mass index, increased maternal weight at booking, lower socioeconomic status, maternal anaemia, and increasing number of cigarettes smoked daily. There were no consistent relations between the placental weight to birthweight ratio and measures of newborn size. CONCLUSIONS: The ratio of placental weight to birth weight is not an accurate marker of fetal growth. In its role as a predictor of adult disease the ratio may be acting as a surrogate for other factors which are already known to influence health and may act before or after birth. Determining the role that relative growth rates of the fetus and placenta have in predisposing to adult disease requires prospective study to account for the many confounding variables which complicate this hypothesis.     

Executive functions of six-year-old boys with normal birth weight and gestational age

Impaired fetal development, reflected by low birth weight or prematurity, predicts an increased risk for psychopathology, especially attention deficit hyperactivity disorder (ADHD). Such effects cut across the normal range of birth weight and gestation. Despite the strength of existing epidemiological data, cognitive pathways that link fetal development to mental health are largely unknown. In this study we examined the relation of birth weight (>2500 g) and gestational age (37-41 weeks) within the normal range with specific executive functions in 195 Singaporean six-year-old boys of Chinese ethnicity. Birth weight adjusted for gestational age was used as indicator of fetal growth while gestational age was indicative of fetal maturity. Linear regression revealed that increased fetal growth within the normal range is associated with an improved ability to learn rules during the intra/extra-dimensional shift task and to retain visual information for short period of time during the delayed matching to sample task. Moreover, faster and consistent reaction times during the stop-signal task were observed among boys born at term, but with higher gestational age. Hence, even among boys born at term with normal birth weight, variations in fetal growth and maturity showed distinct effects on specific executive functions.     

Utilizing Longitudinal Measures of Fetal Growth to Create a Standard Method to Assess the Impacts of Maternal Disease and Environmental Exposure

Impaired or suboptimal fetal growth is associated with an increased risk of perinatal morbidity and mortality. By utilizing readily available clinical data on the relative size of the fetus at multiple points in pregnancy, including delivery, future epidemiological research can improve our understanding of the impacts of maternal, fetal, and environmental factors on fetal growth at different windows during pregnancy. This study presents mean and standard deviation ultrasound measurements from a clinically representative US population that can be utilized for creating Z-scores to this end. Between 2006 and 2012, 18, 904 non-anomalous pregnancies that received prenatal care, first and second trimester ultrasound evaluations, and ultimately delivered singleton newborns at Brigham and Women’s hospital in Boston were used to create the standard population. To illustrate the utility of this standard, we created Z-scores for ultrasound and delivery measurements for a cohort study population and examined associations with factors known to be associated with fetal growth. In addition to cross-sectional regression models, we created linear mixed models and generalized additive mixed models to illustrate how these scores can be utilized longitudinally and for the identification of windows of susceptibility. After adjustment for a priori confounders, maternal BMI was positively associated with increased fetal size beginning in the second trimester in cross-sectional models. Female infants and maternal smoking were associated with consistently reduced fetal size in the longitudinal models. Maternal age had a non-significant association with increased size in the first trimester that was attenuated as gestation progressed. As the growth measurements examined here are widely available in contemporary obstetrical practice, these data may be abstracted from medical records by investigators and standardized with the population means presented here. This will enable easy extension of clinical data to epidemiologic studies investigating novel maternal, fetal, and environmental factors that may impact fetal growth.     

Cardiac growth in staged human fetuses: an allometric approach

The human cardiac growth was studied on 30 staged fetuses (gestational age ranged from 10 to 38 weeks post conception, WPC). The hearts were quantitatively evaluated considering their weight and the following linear parameters: the pulmonary (da.p.) and aortic (dA) internal diameters, the right (VR) and left (VL) ventricular wall thickness, the ventricular width (dV), and the length "sulcus terminalis-apex cordis" (Lst-apex). The data were correlated with the gestational age by using the allometric method (Y = bX alpha). The equations and the growth curves are presented. In the fetal life, we observe that the body weight is 134 times larger than the heart weight, the Lst-apex is 1.07 times larger than the dV, the da.p. is 1.50 times larger than the dA, and the VL is 1.19 times larger than the VR.     

Growth-related shape changes in the fetal craniofacial complex of humans (Homo sapiens) and pigtailed macaques (Macaca nemestrina): a 3D-CT comparative analysis

This study investigates whether macaques and humans possess a common pattern of relative growth during the fetal period. The fetal samples consist of 16 male pigtailed macaques (mean age, 20.5 gestational weeks) and 17 humans (9 males and 8 females; mean age, 29.5 gestational weeks). For each individual, three-dimensional coordinates of 18 landmarks on the skull were collected from three-dimensional computed tomographic (CT) reconstructed images and two-dimensional CT axial slices. Early and late groups were created from the human (early mean age, 24 weeks, N = 8; late mean age, 34 weeks, N = 9) and macaque samples (early mean age, 17.7 weeks, N = 7; late mean age, 23 weeks, N = 9). Inter- and intraspecific comparisons were made between the early and late groups. To determine if macaques and humans share a common fetal pattern of relative growth, human change in shape estimated from a comparison of early and late groups was compared to the pattern estimated between early and late macaque groups. Euclidean distance matrix analysis was used in all comparisons. Intraspecific comparisons indicate that the growing fetal skull displays the greatest amount of change along mediolateral dimensions. Changes during human growth are primarily localized to the basicranium and palate, while macaques experience localized change in the midface. Interspecific comparisons indicate that the two primate species do not share a common pattern of relative growth, and the macaque pattern is characterized by increased midfacial growth relative to humans. Our results suggest that morphological differences in the craniofacial skeleton of these species are in part established by differences in fetal growth patterns.     

叶酸缺乏致胎鼠宫内发育迟缓及肝脏胰岛素生长因子系统表达变化

目的：叶酸是一种水溶性B族维生素,在体内氨基酸与核苷酸代谢中起重要作用,是胎儿生长发育所必须的营养素。本文通过建立叶酸缺乏的孕鼠模型,探讨叶酸缺乏对胎鼠宫内发育的影响,并研究胎鼠肝脏组织中胰岛素生长因子（IGF）系统的表达变化。方法：雌性C57BL／6J小鼠叶酸缺乏组6只、正常对照组6只,分别饲以不舍叶酸和含2mg叶酸／kg的纯合饲料。四周后与雄鼠交配,于怀孕第13．5天（13．5dpc）对孕鼠剖腹取胎,观察和评价胎鼠发育指标,并对宫内发育迟缓（IUGR）比率进行统计。用Real-timePCR法检测胎鼠肝脏组织中胰岛素生长因子I（IGFI）、胰岛素生长因子I受体（IGFIR）、胰岛素生长因子II（IGFII）、胰岛素生长因子II受体（IGFIIR）、胰岛素生长因子结合蛋白1（IGFBP-1）和胰岛素生长因子结合蛋白3（IGFBP-3）mRNA的相对表达水平。结果：叶酸缺乏组雌鼠合笼前每日体重增长量降低,13．5dpc胎鼠吸收胎和死胎比率升高,胎重下降,IUGR比率显著升高,差异有统计学意义（P〈0．05）;叶酸缺乏组胎鼠肝脏组织中IGFII和IGFIIRmRNA的相对表达水平均低于正常对照组（P〈0．05）,IGFI、IGFIR、IGFBP-1和IGFBP-3mRNA的相对表达水平两组间没有差异（P〉0．05）。结论：叶酸缺乏会导致小鼠孕中期胎鼠IUGR比率升高及胎肝IGFII和IGFIIRmRNA的表达水平降低,提示叶酸缺乏对IGF系统基因的调控,可能与胎鼠I-UGR发生机制有关。     

Blood flows and nutrient uptakes in growth-restricted pregnancies induced by overnourishing adolescent sheep

To establish physiological mechanisms for fetal growth restriction in pregnant adolescent ewes we studied uterine, fetal, and uteroplacental metabolism in ewes offered a high (n = 12) or moderate (n = 10) dietary intake. High intakes decreased placental (226 vs. 414 g, P < 0.001) and fetal weight (3,323 vs. 4,626 g, P < 0.01). Uterine blood flow was reduced absolutely (-36%) but proportional to conceptus weight; umbilical blood flow was reduced absolutely (-37%) and per fetal weight (-15%). Uterine oxygen uptake was decreased per conceptus weight (-14%); there was no change in fetal weight oxygen consumption. Uteroplacental oxygen consumption and clearance were reduced proportional to weight. Similar changes were measured for glucose fluxes and fetal glucose concentration; fetal insulin concentration was reduced. In this model of fetal growth restriction, therefore, maintenance of fetal weight-specific glucose and oxygen consumption rates are producing relative hypoglycemia and hypoxemia. This indicates that increased fetal glucose clearance and/or insulin sensitivity may be operating as compensatory mechanisms to preserve normal fetal metabolism while fetal growth is sacrificed.     

Relationships in red deerCervus elaphus mandibles

Growth in mammals often implies differences in body proportions and tissue development more or less characteristic for different age periods and ontogenetic stages. Mouth morphology is an important functional trait in herbivores, as it may determine both maximal intake rate and possibly level of selectivity. An untested hypothesis is that since individual bones within the skeleton are retarded in growth and development in proportion to their growth intensity at each time interval during periods of restricted nutritional supply, this may potentially affect ultimate skeletal proportions. We analysed data on mandible proportions (anterior:total) of 62 fetuses collected at different stages of growth and 16 776 red deerCervus elaphus Linnaeus, 1758 hinds from 0 to 26 years of age and 24026 males from 0 to 22 years of age harvested during autumns 1965–2001 along the west coast of Norway. At the fetal stage, the mandible proportion was negatively related to body weight and, therefore, declined with age of the fetus. The anterior part of the mandible was initially longer than the posterior part; the mandible proportion was between 0.75–0.8 at the fetal stage, but declined with increasing age. The relationship between mandible proportion and weight was strong for calves, but decreased with increasing age, and the relationship was almost flat when reaching 5 years of age. From 5 years, the anterior and posterior part of the mandible was approximately equal in length and this mandible proportion (0.50–0.51), which was unrelated to weight, remained stable for the rest of the life in both hinds and stags. After they were fully-grown, early conditions (cohort density and climate as measured by the North Atlantic Oscillation) had no measurable effect on ultimate mandible proportions after the effect of body weight was removed.