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Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo. Initally designed to evaluate the internet as a teaching tool for first year medical students, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than one million visitors each month.

Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

WHO International Clinical Trials Registry Platform

The World Health Organization (WHO) has created a new Web site to help researchers, doctors and patients obtain reliable information on high-quality clinical trials. Now you can go to one website and search all registers to identify clinical trial research underway around the world!




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Pregnancy Timeline by SemestersDevelopmental TimelineFertilizationFirst TrimesterSecond TrimesterThird TrimesterFirst Thin Layer of Skin AppearsEnd of Embryonic PeriodEnd of Embryonic PeriodFemale Reproductive SystemBeginning Cerebral HemispheresA Four Chambered HeartFirst Detectable Brain WavesThe Appearance of SomitesBasic Brain Structure in PlaceHeartbeat can be detectedHeartbeat can be detectedFinger and toe prints appearFinger and toe prints appearFetal sexual organs visibleBrown fat surrounds lymphatic systemBone marrow starts making blood cellsBone marrow starts making blood cellsInner Ear Bones HardenSensory brain waves begin to activateSensory brain waves begin to activateFetal liver is producing blood cellsBrain convolutions beginBrain convolutions beginImmune system beginningWhite fat begins to be madeHead may position into pelvisWhite fat begins to be madePeriod of rapid brain growthFull TermHead may position into pelvisImmune system beginningLungs begin to produce surfactant
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development


Grieving before conception — risk to infant?

An elevated infant death rate may be linked to mourning experienced by women in the months before they become pregnant.

A study published in Psychosomatic Medicine: Journal of Biobehavioral Medicine, the official journal of the American Psychosomatic Society, relates statistical evidence of births in Denmark over a 30 year period, reflecting the affect of mourning on mothers and their infants.

"Our findings suggest that the six-month period prior to pregnancy may be a sensitive developmental period with implications for early offspring mortality."

Quetzal A. Class PhD, Developmental Psychology, Biological Psychology, Abnormal Psychology, University of Indiana, study leader.

In contrast, maternal bereavement during pregnancy doesn't affect the infant mortality rate. The study was performed when Dr. Class was a doctoral student at Indiana University and now is a postdoctoral researcher at the University of Chicago.

Using a Danish nationwide birth registry, the researchers analyzed data from all women who gave birth in Denmark between 1979 and 2009. Infant and child mortality rates were compared for women with and without "maternal bereavement" — defined as the death of a parent, sibling, or previously born child — in the months before conception or during pregnancy.

The analysis included data on nearly 1.9 million singleton births. Overall mortality rates were 0.004 percent during the first month of life, 0.002 percent between one month and one year, and 0.001 percent between one and five years.

The results showed increased mortality for infants born to mothers who experienced the death of a family member in the months before conception. After adjustment for other factors, risk of infant death during the newborn period (before one month) was more than 80 percent higher for women with preconception bereavement.

For infant death between one month and one year, risk was about 50 percent higher for women with bereavement before conception. The associations were weakened — but still significant — after further adjustment for gestational age and birth weight.

The increases in infant mortality were significant only between zero and six months before conception. Preconception bereavement had no effect on the risk of child death between age one and five years.

Bereavement during pregnancy was unrelated to infant or child mortality.

While rates of early child mortality are improving, information on the causes of these tragic events is needed to develop effective global prevention programs. One previous study has suggested that grieving around the time of conception might be a risk factor for infant mortality. Other studies suggest that general stressors experienced before conception may impact offspring health.

Adding to that evidence, the new study finds that maternal bereavement within six months before conception is linked to an increased infant mortality rate. While the absolute risks are very low — a small fraction of a percentage point — the relative increases in infant mortality risk may be substantial.

"Bereavement is a major life stressor from both a psychological and physiological perspective," Dr. Class and coauthors write. Grieving may lead to changes in the maternal stress system affecting offspring development — particularly during the vulnerable period of early organ development — or alter the mother's biological preparedness for pregnancy.

The researchers note some important limitations of their study — highlighting the need for replication, examination of the specificity and severity of preconception stressors associated with mortality, and exploration of the biological mechanisms functioning in the preconception period.

Meanwhile, the results add new evidence that maternal bereavement immediately before pregnancy may increase the risk for newborn and infant mortality.

"Overall, this study emphasizes that the preconception period should not be overlooked when it comes to promoting infant health."

Quetzal A. Class PhD

Objective: To identify the impact of timing of prenatal stress exposure on offspring risk for shortened gestational age, preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA), using a population-based sample.

Methods: Swedish longitudinal population registries were linked to study all individuals born in Sweden from 1973 to 2004. Prenatal maternal stress exposure was defined as death of the father of the child or first-degree relative of the mother. Using linear and logistic regression, timing of stress exposure was examined across pregnancy, by month, and by novel periods created based on month of stress exposure findings.

Results: A total of 2,618,777 live-born, singleton infants without congenital anomalies were included; 32,286 were exposed to prenatal maternal stress. Examining associations between stress exposure and outcome by the month revealed that risk increases midgestation, particularly after months 5 and 6. Combining months 1 to 4, 5 and 6, and 7 to 9 as potential periods of differing vulnerability, it was found that stress during period 2 (months 5 and 6) was associated with the greatest risk for shortened gestational age (−0.52 days, standard error = 0.15, p = .0006), PTB (odds ratio [OR], 1.24; 99% confidence interval [CI], 1.08–1.42), LBW (OR, 1.38; 99% CI, 1.19–1.61), and SGA (OR, 1.25; 99% CI, 1.05–1.49).

Conclusions: Risk for shortened GA, PTB, LBW, and SGA are greater post stress exposure during the 5th and/or 6th month of pregnancy. It may be beneficial to refine future analyses to these months. Possible mechanisms include alterations in the hypothalamic-pituitary-adrenal axis and associated stress-responsive molecular regulators.

CRH = corticotropin-releasing hormone; GA = gestational age; HPA = hypothalamic-pituitary-adrenal; LBW = low birth weight; PAPP-A = pregnancy-associated plasma protein-A; PTB = preterm birth; SGA = small for gestational age.

Article: "Preconception Maternal Bereavement and Infant and Childhood Mortality: A Danish Population-Based Study." (doi: 10.1097/PSY.0000000000000229)

About Psychosomatic Medicine
Psychosomatic Medicine, Journal of Biobehavioral Medicine, founded in 1939, is the official peer-reviewed journal of the American Psychosomatic Society. It publishes experimental and clinical studies dealing with various aspects of the relationships among social, psychological, and behavioral factors and bodily processes in humans and animals. Psychosomatic Medicine, Journal of Biobehavioral Medicine is an international, interdisciplinary journal devoted to experimental and clinical investigation in behavioral biology, psychiatry, psychology, physiology, anthropology, and clinical medicine. The print journal is published nine times a year; most articles are published online ahead of print.

About the American Psychosomatic Society
The mission of the American Psychosomatic Society is to promote and advance the scientific understanding and multidisciplinary integration of biological, psychological, behavioral and social factors in human health and disease, and to foster the dissemination and application of this understanding in education and health care.

The American Psychosomatic Society is a worldwide community of scholars and clinicians dedicated to the scientific understanding of the interaction of mind, brain, body and social context in promoting health. The organization is devoted to biopsychosocial research and integrated clinical care, and to providing a forum via its website, Annual Meeting and journal, Psychosomatic Medicine, for sharing this research. Its members are from around the world, including specialists from all medical and health-related disciplines, the behavioral sciences, and the social sciences.

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