Fetal growth after fresh and frozen embryo transfer and natural conception: A population-based register study.

OBJECTIVE: To investigate fetal growth trajectories and risks of small and large for gestational age (SGA and LGA), and macrosomia in pregnancies after fresh and frozen embryo transfer (ET), and natural conception (NC). DESIGN: Longitudinal population-based cohort study. SETTING: Swedish national registers. POPULATION: A total of 196 008 singleton pregnancies between 2013 and 2017. METHODS: Of all singleton pregnancies resulting in live births in the Swedish Pregnancy Register, 10 970 fresh ET, 6520 frozen ET, and 178 518 NC pregnancies with ultrasound data were included. A general least squares model was used to examine the effect of fresh or frozen ET on fetal growth while adjusting for confounders. MAIN OUTCOME MEASURES: Fetal growth velocity. SGA, LGA and macrosomia. RESULTS: At 120 days, fetal weights were lower in fresh ET pregnancies compared with NC pregnancies. Thereafter fresh ET as well as FET fetuses had higher fetal weights than NC fetuses, with no differences between themselves until the second trimester. From 210 days, FET fetuses were heavier than fresh ET fetuses, whereas fresh ET fetuses had lower fetal weights than NC fetuses from 245 days. After fresh ET, SGA was more frequent, whereas LGA and macrosomia were less frequent, than after FET. CONCLUSIONS: This study gives new insights into the differences in fetal growth dynamics between fresh and frozen ET and NC pregnancies. Clinically relevant differences in proportions of SGA, LGA and macrosomia were observed.

Second trimester induced abortions due to fetal anomalies-a population-based study of diagnoses, examinations and clinical management.

INTRODUCTION: Two-thirds of induced abortions after gestational week (gw) 18 are performed due to fetal anomalies. The potential of the fetus to survive outside the uterus after birth is the upper limit for induced abortions in Sweden. Due to advances in neonatal medicine, fetal viability and the upper limit of late induced abortions have been converging over the last few decades. The aim of the study was to examine clinical management of fetal anomalies, including time frames, leading to second trimester abortions. MATERIAL AND METHODS: All induced abortions due to fetal anomalies after gw 11+6 in Uppsala county, Sweden, from 2010 to 2017, were reviewed from electronic medical records in a retrospective descriptive study. In total, 180 women underwent 185 abortions divided into 107 (57.8%) in an early group (gw 12+0 to 18+0), and 78 (42.2%) in a late group (≥ gw 18+1). Examinations performed were genetic testing, fetal echocardiography, magnetic resonance imaging (MRI) and pediatric counseling. Time frames from suspicion of fetal anomaly to abortion were reviewed. RESULTS: Anomalies were subdivided into groups of diagnosis: chromosomal (n = 104), central nervous system (n = 22), heart (n = 12), urinary tract (n = 10) and others (n = 37). Chromosomal anomaly was present in 82 (76.6%) in the early group and 22 (28.2%) in the late group. In the early group, examinations performed preceding a conclusive diagnosis were mainly QF-PCR for trisomies (n = 97), microarray (n = 13), and genetic counseling (n = 14). In the late group, trisomy test was performed in 68, microarray in 31, MRI in 24, fetal echocardiography in 28, and pediatric or genetic counseling in 43 and six cases, respectively. Mean time interval from suspicion of fetal anomaly to the woman's decision was 5 days before gw 18+1, 7 days in gw 18, and 13 days in gw 21. More than two examinations before reaching the decision to terminate the pregnancy were needed in two abortions (25.0%) in gw 18, increasing to 16 (80.0%) in gw 21. CONCLUSIONS: Increasing complexity and diversity in fetal diagnoses require time-consuming examinations in late-induced abortions compared with earlier gestational weeks. A structured expedient process is necessary to allow for decision time and minimize terminations approaching the legal limit.

Temperature and predator-mediated regulation of plasma cortisol and brain gene expression in juvenile brown trout (Salmo trutta).

BACKGROUND: Temperature affects many aspects of performance in poikilotherms, including how prey respond when encountering predators. Studies of anti-predator responses in fish mainly have focused on behaviour, whereas physiological responses regulated through the hypothalamic-pituitary-interrenal axis have received little attention. We examined plasma cortisol and mRNA levels of stress-related genes in juvenile brown trout (Salmo trutta) at 3 and 8 °C in the presence and absence of a piscivorous fish (burbot, Lota lota). RESULTS: A redundancy analysis revealed that both water temperature and the presence of the predator explained a significant amount of the observed variation in cortisol and mRNA levels (11.4 and 2.8%, respectively). Trout had higher cortisol levels in the presence than in the absence of the predator. Analyses of individual gene expressions revealed that trout had significantly higher mRNA levels for 11 of the 16 examined genes at 3 than at 8 °C, and for one gene (retinol-binding protein 1), mRNA levels were higher in the presence than in the absence of the predator. Moreover, we found interaction effects between temperature and predator presence for two genes that code for serotonin and glucocorticoid receptors. CONCLUSIONS: Our results suggest that piscivorous fish elicit primary stress responses in juvenile salmonids and that some of these responses may be temperature dependent. In addition, this study emphasizes the strong temperature dependence of primary stress responses in poikilotherms, with possible implications for a warming climate.

Postnatal growth in children born small for gestational age with and without smoking mother.

BACKGROUND: Maternal smoking impairs fetal growth; however, if postnatal growth differs between children born small for gestational age (SGA) with smoking and non-smoking mother is unknown. METHODS: Cohort-study of term born children born appropriate for gestational age with non-smoking mother (AGA-NS, n = 30,561), SGA (birthweight <10th percentile) with smoking mother (SGA-S, n = 171) or SGA with non-smoking mother (SGA-NS, n = 1761). Means of height and weight measurements, collected at birth, 1.5, 3, 4, and 5 years, were compared using a generalized linear mixed effect model. Relative risks of short stature (<10th percentile) were expressed as adjusted risk ratios (aRR). RESULTS: At birth, children born SGA-S were shorter than SGA-NS, but they did not differ in weight. At 1.5 years, SGA-S had reached the same height as SGA-NS. At 5 years, SGA-S were 1.1 cm taller and 1.2 kg heavier than SGA-NS. Compared with AGA-NS, SGA-S did not have increased risk of short stature at 1.5 or 5 years, while SGA-NS had increased risk of short stature at both ages; aRRs 3.0 (95% CI 2.6;3.4) and 2.3 (95% CI 2.0;2.7), respectively. CONCLUSIONS: Children born SGA-S have a more rapid catch-up growth than SGA-NS. This may have consequences for metabolic and cardiovascular health in children with smoking mothers.

Chronic Hypertension in Women after Perinatal Exposure to Preeclampsia, Being Born Small for Gestational Age or Preterm.

BACKGROUND: There is an established association between adverse events during perinatal life and chronic hypertension in adult life. However, disadvantageous conditions often co-exist in the same pregnancy. We investigated single and joint perinatal exposure to preeclampsia, being born small for gestational age (SGA) or preterm and subsequent risk of chronic hypertension. METHODS: The study population consisted of 731 008 primiparous women from Norway and Sweden registered in the Medical Birth Registers, both as infants and as first time mothers between 1967-2009 (Norway) and 1973-2010 (Sweden). Risk of chronic hypertension in early pregnancy was calculated in women with perinatal exposures to preeclampsia, born SGA or preterm by log-binominal regression analysis, and adjusted for maternal age and level of education in the first generation. RESULTS: The rate of chronic hypertension was 0.4%. Risk of chronic hypertension was associated with single perinatal exposure to preeclampsia, being born SGA or preterm with adjusted relative risk (95% confidence interval, CI) of 2.2 (95% CI 1.8, 2.7), 1.1 (95% CI 1.0, 1.3), and 1.3 (95% CI 1.0, 1.5) respectively. The risks increased after joint exposures, with an almost fourfold risk increase after perinatal exposure to preeclampsia and preterm birth. Additional adjustment for BMI and smoking in the second generation in a subset of the cohort only had a minor impact on the results. CONCLUSIONS: Perinatal exposure to preeclampsia, being born SGA or preterm is independently associated with increased risk of chronic hypertension. The highest risk was seen after exposure to preeclampsia, especially if combined with SGA or preterm birth.

Ice cover affects the growth of a stream-dwelling fish.

Protection provided by shelter is important for survival and affects the time and energy budgets of animals. It has been suggested that in fresh waters at high latitudes and altitudes, surface ice during winter functions as overhead cover for fish, reducing the predation risk from terrestrial piscivores. We simulated ice cover by suspending plastic sheeting over five 30-m-long stream sections in a boreal forest stream and examined its effects on the growth and habitat use of brown trout (Salmo trutta) during winter. Trout that spent the winter under the artificial ice cover grew more than those in the control (uncovered) sections. Moreover, tracking of trout tagged with passive integrated transponders showed that in the absence of the artificial ice cover, habitat use during the day was restricted to the stream edges, often under undercut banks, whereas under the simulated ice cover condition, trout used the entire width of the stream. These results indicate that the presence of surface ice cover may improve the energetic status and broaden habitat use of stream fish during winter. It is therefore likely that reductions in the duration and extent of ice cover due to climate change will alter time and energy budgets, with potentially negative effects on fish production.

Effects of initial leaching for estimates of mass loss and microbial decomposition-Call for an increased nuance.

Decomposition is essential to carbon, nutrient, and energy cycling among and within ecosystems. Several methods have been proposed for studying litter decomposition by using a standardized and commercially available substrate. One of these methods is the Tea Bag Index (TBI) which uses tea bags (green and rooibos tea) incubated for ~90 days. The TBI is now applied all over the globe, but despite its usefulness and wide application, the TBI (as well as other methods) does not explicitly account for the differences in potential loss of litter mass due to initial leaching in habitats with large differences in moisture. We, therefore, studied the short-term mass losses (3-4 h) due to initial leaching under field and laboratory conditions for green and rooibos tea using the TBI and contextualized our findings using existing long-term mass loss (90 days) in the field for both aquatic and terrestrial environments. For both tea litter types, we found a fast initial leaching rate, which could be mistaken for decomposition through microbial activity. This initial leaching was higher than the hydrolyzable fraction given in the description of the TBI. We also found that leaching increased with increasing temperature and that leaching in terrestrial environments with high soil moisture (>90%) is almost as large as in aquatic environments. When comparing our findings to long-term studies, we found that up to 30-50% of the mass loss of green tea reported as decomposition could be lost through leaching alone in high moisture environments (>90% soil moisture and submerged). Not accounting for such differences in initial leaching across habitats may lead to a systematic overestimation of the microbial decomposition in wet habitats. Future studies of microbial decomposition should adjust their methods depending on the habitat, and clearly specify the type of decomposition that the study focuses on.

Perinatal and 2-year neurodevelopmental outcome in late preterm fetal compromise: the TRUFFLE 2 randomised trial protocol.

INTRODUCTION: Following the detection of fetal growth restriction, there is no consensus about the criteria that should trigger delivery in the late preterm period. The consequences of inappropriate early or late delivery are potentially important yet practice varies widely around the world, with abnormal findings from fetal heart rate monitoring invariably leading to delivery. Indices derived from fetal cerebral Doppler examination may guide such decisions although there are few studies in this area. We propose a randomised, controlled trial to establish the optimum method of timing delivery between 32 weeks and 36 weeks 6 days of gestation. We hypothesise that delivery on evidence of cerebral blood flow redistribution reduces a composite of perinatal poor outcome, death and short-term hypoxia-related morbidity, with no worsening of neurodevelopmental outcome at 2 years. METHODS AND ANALYSIS: Women with non-anomalous singleton pregnancies 32+0 to 36+6 weeks of gestation in whom the estimated fetal weight or abdominal circumference is <10th percentile or has decreased by 50 percentiles since 18-32 weeks will be included for observational data collection. Participants will be randomised if cerebral blood flow redistribution is identified, based on umbilical to middle cerebral artery pulsatility index ratio values. Computerised cardiotocography (cCTG) must show normal fetal heart rate short term variation (≥4.5 msec) and absence of decelerations at randomisation. Randomisation will be 1:1 to immediate delivery or delayed delivery (based on cCTG abnormalities or other worsening fetal condition). The primary outcome is poor condition at birth and/or fetal or neonatal death and/or major neonatal morbidity, the secondary non-inferiority outcome is 2-year infant general health and neurodevelopmental outcome based on the Parent Report of Children's Abilities-Revised questionnaire. ETHICS AND DISSEMINATION: The Study Coordination Centre has obtained approval from London-Riverside Research Ethics Committee (REC) and Health Regulatory Authority (HRA). Publication will be in line with NIHR Open Access policy. TRIAL REGISTRATION NUMBER: Main sponsor: Imperial College London, Reference: 19QC5491. Funders: NIHR HTA, Reference: 127 976. Study coordination centre: Imperial College Healthcare NHS Trust, Du Cane Road, London, W12 0HS with Centre for Trials Research, College of Biomedical & Life Sciences, Cardiff University. IRAS Project ID: 266 400. REC reference: 20/LO/0031. ISRCTN registry: 76 016 200.

Self-administered symphysis-fundus measurements analyzed with a novel statistical method for detection of intrauterine growth restriction: a clinical evaluation.

OBJECTIVE: To assess the ability of self-administered symphysis-fundus measurements used with the Shiryaev-Roberts statistical method (SR method) to identify growth-restricted (IUGR) fetuses and compare it with the traditional SF method (symphysis-fundus measurements used with a population-based reference curve). DESIGN: Longitudinal study. SETTING: Pregnant women attending primary antenatal care centres. POPULATION: From a population of 1 888 women with singleton ultrasound-dated pregnancies, we analyzed data from 1 122 women. METHODS: Weekly self-administered SF measurements from gestational week 25 until delivery were analyzed according to the SR method. Neonatal morbidity and small for gestational age (SGA) were used as proxies for IUGR. Small for gestational age was defined as a birthweight less than two standard deviations (SD) and <10th percentile. We assessed the sensitivity of the SR and the SF methods to detect neonatal morbidity and SGA. MAIN OUTCOME MEASURES: Birth-related mortality, respiratory distress, hypoglycemia, Apgar score ≤6 at five minutes, pH ≤7.00 in the umbilical artery, neonatal care, preterm delivery, operative delivery for fetal distress and SGA. Results. For the SR method, the sensitivity for neonatal morbidity was between 6.0 and 36.4%, for SGA <2SD 36.8%, and for SGA <10th percentile 20.9%. The SF method had a sensitivity between 6.0 and 13.8% for neonatal morbidity, 52.3% for SGA <2SD and 28.6% for SGA <10th percentile. CONCLUSIONS: The SR and the SF methods had low sensitivities for neonatal morbidity.

Relative growth estimated from self-administered symphysis fundal measurements.

OBJECTIVE: To establish absolute- and relative-growth reference curves for the detection of intrauterine growth restriction from weekly self-administered symphysis-fundus (SF) measurements and to assess the influence of fetal sex, maternal obesity and parity. DESIGN: Prospective longitudinal study. SETTING: Pregnant women from six primary antenatal care centres. POPULATION: Three hundred women with singleton ultrasound dated pregnancies. METHODS: Weekly self-administered SF measurements from gestational week 25 until delivery were obtained. A linear mixed longitudinal model was used to estimate the absolute SF growth using the natural logarithm (lnSF). Relative lnSF growth was calculated as the lnSF measurement in one gestational week subtracted by the lnSF measurement in the previous gestational week. The influence of fetal sex, maternal obesity and parity was assessed in regression models and by a graphical display. MAIN OUTCOME MEASURES: Absolute lnSF and relative lnSF growth curves and influence of fetal sex, maternal obesity and parity on these. RESULTS: SF measurements from 191 women were used to establish an SF-growth reference. The absolute lnSF growth was influenced by maternal obesity, and for fetal sex and parity, borderline significance was recorded; while there was no evidence that the relative lnSF growth could depend on these variables. CONCLUSIONS: Weekly self-administered SF measurements can be obtained and used to estimate SF growth. Relative growth of the lnSF height seems to be independent of fetal sex, maternal obesity and parity.

Does one's sense of coherence change after an acute myocardial infarction? A two-year longitudinal study in Sweden.

The aim of this study was to assess changes in the sense of coherence of patients who had suffered their first myocardial infarction. Out of 100 patients at the start of the study, these changes were evaluated in 66 men and 18 women aged 36-70 years. Generally, the sense of coherence was found to be stable among the whole group, but there were significant individual variations in its development in some of the participants over the following years. Even the individuals with an initally high sense of coherence could experience a decrease in its level. The changes that were found in the men can be explained by their marital status, level of treatment satisfaction, disease perception/quality of life, physical limitation, and alcohol intake and/or tobacco use at the baseline. An unexpected finding was that the single men with an initially high sense of coherence experienced a decreased level over time. In order to maintain or increase patients' sense of coherence, it is important for nurses to help them identify their risk factors and to provide conditions for individualized cardiac rehabilitation in order to avoid another myocardial infarction.

Swedish intrauterine growth reference ranges for estimated fetal weight.

Fetal growth restriction is a strong risk factor for perinatal morbidity and mortality. Reliable standards are indispensable, both to assess fetal growth and to evaluate birthweight and early postnatal growth in infants born preterm. The aim of this study was to create updated Swedish reference ranges for estimated fetal weight (EFW) from gestational week 12-42. This prospective longitudinal multicentre study included 583 women without known conditions causing aberrant fetal growth. Each woman was assigned a randomly selected protocol of five ultrasound scans from gestational week 12 + 3 to 41 + 6. Hadlock's 3rd formula was used to estimate fetal weight. A two-level hierarchical regression model was employed to calculate the expected median and variance, expressed in standard deviations and percentiles, for EFW. EFW was higher for males than females. The reference ranges were compared with the presently used Swedish, and international reference ranges. Our reference ranges had higher EFW than the presently used Swedish reference ranges from gestational week 33, and higher median, 2.5th and 97.5th percentiles from gestational week 24 compared with INTERGROWTH-21st. The new reference ranges can be used both for assessment of intrauterine fetal weight and growth, and early postnatal growth in children born preterm.

Associations of ultrasound estimated early mid pregnancy visceral and subcutaneous fat depths and early pregnancy BMI with adverse neonatal outcomes.

This study investigated whether maternal central adiposity and body mass index (BMI) were associated with neonatal hypoglycemia and adverse neonatal outcomes. A cohort study was performed at Uppsala University Hospital, Sweden, between 2015 and 2018. Visceral and subcutaneous fat depths were measured by ultrasound at the early second-trimester anomaly scan in 2771 women giving birth to singleton infants. Body mass index was assessed in early pregnancy. Logistic regression models were performed. Adjustments were made for age, BMI (not in model with BMI as exposure), smoking, maternal country of birth, and parity. Outcomes were neonatal hypoglycemia (blood glucose concentration < 2.6 mmol/l), a composite of adverse neonatal outcomes (Apgar < 7 at 5 min of age, or umbilical artery pH ≤ 7.0, or admission to neonatal intensive care unit), and the components of the composite outcome. Visceral and subcutaneous fat depths measured by ultrasound in early mid pregnancy were not associated with any of the outcomes in adjusted analyses. For every unit increase in BMI, the likelihood of neonatal hypoglycemia increased by 5% (aOR 1.05, 95% CI 1.01-1.10), the composite outcome by 5% (aOR 1.05, 95% CI 1.01-1.08), and admission to neonatal intensive care unit by 6% (aOR 1.06, 95% CI 1.02-1.10).

Swedish intrauterine growth reference ranges of biometric measurements of fetal head, abdomen and femur.

Ultrasonic assessment of fetal growth is an important part of obstetric care to prevent adverse pregnancy outcome. However, lack of reliable reference ranges is a major barrier for accurate interpretation of the examinations. The aim of this study was to create updated Swedish national reference ranges for intrauterine size and growth of the fetal head, abdomen and femur from gestational week 12 to 42. This prospective longitudinal multicentre study included 583 healthy pregnant women with low risk of aberrant fetal growth. Each woman was examined up to five times with ultrasound from gestational week 12 + 3 to 41 + 6. The assessed intrauterine fetal biometric measurements were biparietal diameter (outer-inner), head circumference, mean abdominal diameter, abdominal circumference and femur length. A two-level hierarchical regression model was employed to account for the individual measurements of the fetus and the number of repeated visits for measurements while accounting for the random effect of the identified parameterization of gestational age. The expected median and variance, expressed in both standard deviations and percentiles, for each individual biometric measurement was calculated. The presented national reference ranges can be used for assessment of intrauterine size and growth of the fetal head, abdomen and femur in the second and third trimester of pregnancy.

Association of maternal central adiposity measured by ultrasound in early mid pregnancy with infant birth size.

We sought to investigate whether early mid pregnancy visceral and subcutaneous fat depths measured by ultrasound were associated with infant birth size, independent of early pregnancy BMI. A cohort study was performed at Uppsala University Hospital, Sweden, between 2015-2018. Visceral and subcutaneous fat depths were measured at the early second-trimester anomaly scan in 2498 women, giving birth to singleton, term infants. Primary outcomes were birthweight and LGA (birthweight standard deviation score > 90th percentile in the cohort). Linear and logistic regression models were used, adjusted for BMI, age, smoking, parity, maternal country of birth, gestational age and infant sex. A 5-mm increase in visceral fat depth was associated with an increase in birthweight of 8.3 g [95% confidence interval (CI) 2.5 - 14.1 g], after adjustments, and a 6% increase in the adjusted odds of having an infant born LGA (OR 1.06, CI 1.02-1.11). There was no association between subcutaneous fat depth and birthweight or LGA after covariate adjustments. Hence, visceral fat depth measured by ultrasound in early mid pregnancy was associated with excessive fetal growth, independent of early pregnancy BMI, and may be useful in models for predicting LGA infants.

Review of real-time release testing of pharmaceutical tablets: State-of-the art, challenges and future perspective.

In the last decade significant advances have been made in process analytical technologies and digital manufacturing of pharmaceutical oral solid dosage forms leading to enhanced product knowledge and process understanding. These developments provide an excellent platform for realising real-time release testing (RTRT) to eliminate all, or certain, off-line end product tests assuring that the drug product is of intended quality. This review article presents the state of the art, an RTRT development workflow as well as challenges and opportunities of RTRT in batch and continuous manufacturing of pharmaceutical tablets. Critical quality attributes, regulatory aspects and the scientific basis of enabling technologies and models for RTRT are discussed and a systematic development workflow for the robust design of an RTRT environment is presented. This includes the discussion of key considerations for the identification of the critical quality attributes and points of testing as well as the development of the sampling strategy, a hard and/or soft sensor approach and operational procedures. The final sections present two RTRT use cases in an industrial setting as well as critically discuss challenges and provide a future perspective of RTRT.

Growth patterns during early childhood in children born small for gestational age and moderate preterm.

Today we lack knowledge if size at birth and gestational age interact regarding postnatal growth pattern in children born at 32 gestational weeks or later. This population-based cohort study comprised 41,669 children born in gestational weeks 32-40 in Uppsala County, Sweden, between 2000 and 2015. We applied a generalized least squares model including anthropometric measurements at 1.5, 3, 4 and 5 years. We calculated estimated mean height, weight and BMI for children born in week 32 + 0, 35 + 0 or 40 + 0 with birthweight 50th percentile (standardized appropriate for gestational age, sAGA) or 3rd percentile (standardized small for gestational age, sSGA). Compared with children born sAGA at gestational week 40 + 0, those born sAGA week 32 + 0 or 35 + 0 had comparable estimated mean height, weight and BMI after 3 years of age. Making the same comparison, those born sSGA week 32 + 0 or 35 + 0 were shorter and lighter with lower estimated mean BMI throughout the whole follow-up period. Our findings suggest that being born SGA and moderate preterm is associated with short stature and low BMI during the first five years of life. The association seemed stronger the shorter gestational age at birth.

Born Small for Gestational Age and Poor School Performance - How Small Is Too Small?

AIM: To assess the relationship between severity of small for gestational age (SGA) and the risk of poor school performance, and to investigate whether adult stature modifies this risk. METHODS: 1,088,980 Swedish children born at term between 1973 and 1988 were categorized into severe SGA (less than -3 standard deviations (SD) of expected birth weight), moderate SGA (-2.01 to -3 SD), mild SGA (-1.01 to -2 SD), and appropriate for gestational age (-1 to 0.99 SD). The risk of poor school performance at the time of graduation from compulsory school (grades <10th percentile) was calculated using unconditional logistic regression models and adjusted for socio-economic factors. In a sub-analysis, we stratified boys by adult stature, and adjusted for maternal but not paternal height. RESULTS: All SGA groups were significantly associated with an increased risk of poor school performance, with adjusted odds ratios and 95% confidence intervals ranging from 1.85 (1.65-2.07) for severe SGA to 1.25 (1.22-1.28) for mild SGA. In the sub-analysis, all birth weight groups were associated with an increased risk of poor school performance among boys with short stature compared to those with non-short stature. CONCLUSION: Mild SGA is associated with a significantly increased risk of poor school performance, and the risk increases with severity of SGA. Further, this risk diminishes after adequate catch-up growth.

Environmentally induced migration: the importance of food.

The decision to migrate or not is regarded as genetically controlled for many invertebrate and vertebrate taxa. Here, we show that the environment influences this decision. By reciprocally transplanting brown trout (Salmo trutta L.) between two sections in a river, we show that both migratory and non-migratory behaviour can be environmentally induced; migratory behaviour developed in a river section with high brown trout densities and low specific growth rates, whereas non-migratory behaviour developed in a section with low brown trout densities and high specific growth rates. In a laboratory experiment, we tested the effect of food availability on the development of migratory and non-migratory body morphologies and found that most brown trout became migrants when food levels were low but fewer did so at high food levels. Thus, the decision to migrate seems to be a plastic response, influenced by growth opportunities.