Carnegie Stages - 1st Trimester Pregnancy2nd Trimester Pregnancy3rd Trimester PregnancyCarnegie Stage 1 - Fertilization Carnegie Stage 2 - CleavageCarnegie Stage 3 - Early BlastocystCarnegie Stage 4 - ImplantationCarnegie Stage 5 - Implantation CompletedCarnegie Stage 6 - GastrulationCarnegie Stage 7 - NeurulationCarnegie Stage 8 - Primitive PitCarnegie Stage 9 - First SomitesCarnegie Stage 10 - Neural Folds, Heart TubeCarnegie Stage 11 - Optic VesicleCarnegie Stage 12 - Upper Limb BudsCarnegie Stage 13 - First Layer Skin Carnegie Stage 14 - Esophagus FormingCarnegie Stage 15 - Cerebral Hemispheres FormingCarnegie Stage 16 - Hindbrain DevelopingCarnegie Stage 17 - Primitive germ cellsCarnegie Stage 19 - Semicircular Canals Forming in Inner EarCarnegie Stage 20 - Spontaneous MovementCarnegie Stage 21 - Intestines MigrateCarnegie Stage 22 - Brain can move musclesCarnegie Stage 23 - End of embryonic developmentWeeks 10 to 11 - Basic Brain Structure CompleteWeeks 12 to 13 - Fetus begins to move aroundWeeks 14 to 15 - Sexual organs now clearly visibleWeeks 16 to 17 - Fingerprints and toe prints beginWeeks 18 to 19 - Brown fat surrounds the lymphatic system.Weeks 20 to 21 - Bone marrow starts making blood cellsWeeks 22 to 23 - Inner ear bones harden, hearing possibleWeeks 24 to 25 - Sensory brain waves begin to activateWeeks 26 to 27 - Lungs begin to produce sufacantWeeks 28 to 29 - Brain Surface Convolutions BeginWeeks 39 to 40 - Baby full termWeeks 41 - 41 Baby full termWeeks 38 to 39 - Fetal liver is producing blood cellsWeeks 36 to 37 - Body is round and plump with white fatWeeks 34 to 35 - Gastrointestinal system still very immatureWeeks 32 to 33 - Fetus begins to develop immune systemWeeks 30 to 31 - Rapid brain growth; head size increasesPregnancy - 1st TrimesterPregnancy - 1st Trimester

The Visible Embryo
is a visual guide through fetal development from fertilization through pregnancy to birth. As the most profound physiologic changes occur in the "first trimester" of pregnancy, these Carnegie stages are given prominence on the birth spiral.

The shape and location of embryonic
internal structures and how they
relate and are connected to each
other is essential to understanding
human development. Medical
professionals create a mental picture
of this process in order to determine
how well the fetus is progressing. It is
also the basis of knowing how and when
errors in development occur and if a
possibility exists for a corrective

It is equally important for expectant
parents to understand the relationship
of these internal structures and how
their infant develops through pregnancy.

Creating the images for The Visible Embryo, included capturing data from slides and three dimensional structures on fetal anatomy in The National Institutes of Health, Carnegie Collection of embryos, as well as from 3D and 4D ultra sound images.

Disclaimer: The Visible Embryo web site is provided for your general information only. The information contained on this site should not be treated as a substitute for medical,legal or other professional advice. Neither is The Visible Embryo responsible or liable for the contents of any websites of third parties which are listed on this site.


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News Alerts  Oct 2016   Birth Spiral "Fixing" energy signals to treat mitochondrial disease Birth Spiral How eggs get the wrong number of chromosomes Birth Spiral Fatal preemie disease due to mitochondrial failure Birth Spiral Zika virus spreads during brain growth spurts Birth Spiral New links between genes and bigger brains Birth Spiral Short jump from single-cell to multi-cell animals Birth Spiral Brainstem and visual cortex control our eyes Birth Spiral Embryos make sex cells in their first two weeks Birth Spiral Mom's BMI may affect biological age of her baby Birth Spiral Two distinct cell types can initiate Crohn's disease Birth Spiral Potential treatment of newborns via amniotic fluid? Birth Spiral Infants use their prefrontal cortex to learn Birth Spiral 'Amplifier' helps make connections in the fetal brain Birth Spiral Neurons migrate throughout infancy Birth Spiral Calcium triggers stem cells to generate bone Birth Spiral How evolution has given us 5 fingers Birth Spiral New links between genes and bigger brains  Birth Spiral Progesterone in contraceptives promotes flu healing Birth Spiral ZIKA in Men? "No procreation for 6 months" Birth Spiral Genetically modified baby boy - with 3 parents Birth Spiral Meet the world's largest bony fish Birth Spiral Genetic variations that cause skull-fusion disorders Birth Spiral Heart defect genes both inside and outside the heart Birth Spiral Cesarean baby 15% more likely to become obese Birth Spiral Male primes female for reproduction - but at a cost Birth Spiral Why Tardigrades Are So Indestructible Birth Spiral Mouse bone marrow cells reduce miscarriage? Birth Spiral How maternal genes give control to embryonic genes Birth Spiral Gene linked to infertility in male mice Birth Spiral High food availability slows down cell aging Birth Spiral Zika brain injury therapy must start at time of bite Birth Spiral How GBS bacteria can cause preterm birth Birth Spiral Scientists make embryos from non-egg cells Birth Spiral Placenta pivotal in influencing pregnancy outcome Birth Spiral How does a cell initiate DNA repair Birth Spiral lncRNA structure affects its function Birth Spiral Cell fate a result of genetic tugs of war Birth SpiralUnlocking first steps in organ and tissue development Birth Spiral Stem cells differ in mice, monkeys, and humans Birth Spiral Chemicals from fracking may harm fertility Birth Spiral Checkmating the "Red King Theory" Birth Spiral  Morrbid gene fights infection havoc  Sep 2016  Birth Spiral A protein that promotes the breakdown of fat Birth Spiral Immune cells active in brain development  Birth Spiral Face shape is in our genes Birth Spiral Two proteins preserve vital genetic information Birth Spiral A molecular alarm clock wakes resting eggs Birth Spiral Risk factors for preterm birth can be changed Birth Spiral Zika infection may affect adult brain cells Birth Spiral How fish fins became fingers Birth Spiral Plastic BPS chemical harms human egg cells  Birth Spiral Customizing breast milk for premature children Birth Spiral Mom in Single Family NICU room is best for preemies Birth Spiral Jaw-dropping research explains how mouth forms Birth Spiral A vaccine for strep throat and rheumatic fever? Birth Spiral Is there a 'mother's curse' ? Birth Spiral Non-Zika microcephaly helps explain brain growth Birth Spiral Tall or short, thick or thin what affects limb size? Birth Spiral Signals that trigger labor and delivery Birth Spiral Breakthrough in how stem cells become specialized Birth Spiral The force is strong — with embryo cells Birth Spiral  Common diabetes drug may help prevent preterm birth Birth Spiral Origin of the female orgasm Birth Spiral Breastfeeding builds better brains Birth Spiral Embryonic gene, Nanog, can reverse cell aging Aug 2016 Birth Spiral Makeup therapy in a down economy Birth Spiral Cinnamon may be a fragrant medicine for the brain Birth Spiral A molecule for making friends  Pyramid cells cluster, vibrate and signal our brain  How environmental stresses cause birth defects  Virus found in women with unexplained infertility Pregnant nicotine exposure higher than reported Cells send out stop/go signals to extend nerves Anatomy of a decision Sound waves to separate twin placentas?  Selfish mitochondria implicated in diseases  Powering up: growing neurons make an energy jump  Virus in pregnancy linked to austim disorders Bipolar disorder link to striatum brain region Epigenetics could explain puzzle of diabetes inheritance   Many common chemicals endanger brain development  Children's immune cells may explain all their illnesses "Feeling good" stimulates immune system How the Pentagone protein controls development   Why does mitochondria DNA only come from mom?  Finding human development's first gear  July 2016    Study shows Zika infection longer in pregnancy  Daughters of obese mouse dads risk breast cancer CDC clinical trial for experimental Zika vaccine Saint Louis University to launch Zika vaccine trial  Loss of essential protein linked to hydrocephalus Low thyroid in pregnancy risks schizophrenia in baby Teen poor attention control risk for anxiety disorders Pregnant diet can affect multiple generations New insights uncovered in Prader-Willi syndrome Breastmilk best for premature baby's heart Gene mutation found explaining multiple sclerosis Individuals respond differently to Zika?  Moving can be hazardous to your child's health How melanin gives color to skin, hair and eyes Babies really are cute! Your biological clock has a time stamp   Maternal effects of smoking continue long after birth  A brain clock keeps our memories ticking  Gene sequencing diagnoses rare newborn diseases The developmental origins of culture How the brain makes — and breaks — a habit Jun 2016 Money really does matter in relationships   Executive power — developes from the nursery  Can lifespan be extended by point of view?  Mitochondrial DNA therapy still imperfect  Eating fruit prenatally boosts babies' cognition  BPA in pregnancy can put baby on course to obesity  Genes for nose shape identified  Neurons must wriggle to reach their final destination  Atlas of Human Malformation Syndromes being created  Fathers' age and lifestyle linked to birth defects A safe way to deliver drugs to the placenta  Zika causes neural stem cells to self-destruct  Scientists map brain to decode inner thoughts  You are what you eat!  Twin study finds gut microbiomes run in families  Another reason to breastfeed Breast milk fed preemies show larger brain growth An aggregate of protein in nerve cells can cause ALS  How did human limbs evolve?  Asynchronous waves key to embryo development  A cell's 'fuel gauge' promotes healthy development  Safe, inexpensive chemical reverses progeria  Confused cell signals lead to genetic disorders May 2016| Experimental drug cancels affect of Fragile X gene  Preschool nurturing boosts child's brain growth  Too much 'noise' can affect brain development  Human patterns follow the same cues as bacteria  The unique biology of human breast milk  Clues to how cells repair broken DNA First protein crystal structure corrects wrong theory  Deletions on chromosome 22, one cause of autism? Microvesicles for brain radiation recovery?  New type of cell death may help neurons regenerate  Single-cell embryos can be chimeras  Trophoblast cells unlikely entry point for Zika  Gene found for cleft palate  An overfed fetus can become an overweight teen  Three generations affected by one DDT exposure  How early female human embryos control X  Abnormalities in early embryos may self correct  How to prevent asthma in your newborn?    Protein on neural stem cell is hijacked by Zika virus  Fragile X in mice responds to experimental drug  Born to run? Apr 2016   Unraveling stem cells  Rewrite the text books! Fetal or placental cells? Precision medicine targets Lupus Cell 'rejuvenation' relies on telomeres PKU effect on brain more extensive than thought  A possible treatment for autism-like symptoms Complex learning dismantles barriers in the brain Can we turn off Alzheimer's disease?  A new kind of stem cell? Genes can cause neurological diseases  Brown fat in adults follows circadian rhythm  Mom's bacterial infection can change fetal brain  Zika virus breakthrough  Lack of stem cells causes recurring miscarriages  A first: earliest stages of human stem cell lines  One microRNA may affect many neuro disorders  Common gene links obesity to diabetes Perception of constant stress is passed on...   Snail shells help solve origins of body symmetry  Trimmer snips jumping genes  Mom's high alcohol level disrupts neonatal brain  Amino acids help kids overcome fetal malnutrition  Mar 2016   Zika virus linked to stillbirth, loss of brain tissue  How to regenerate peripheral nerves  How the nervous system trims its branches   Teaching stem cells to build muscle  'Pump' mechanism splits DNA for copying by RNA Stressed dads give offspring high blood sugar Cell division errors: infertility, disorders and cancers Copper key to brain cell development Bioelectric signals influence facial symmetry   Potential to treat hypertrophic cardiomyopathy   Fluorescent proteins light up living cells Tuning the volume on gene expression  Linking fetal to adult brain disorders  A quick, simple way to generate neural crest cells  New drug target for Rett syndrome  RNA quick — Protein slow   Mitochondria trigger cell aging  How to precisely regulate RNA polymerase? New app helps doctors predict preterm birth   Found - protein that turns off biological clock   Virus in pregnancy causes autism-like behavior Feb 2016    A gene that allows for a new species?  3 Autism-linked molecules wire up neurons   Donor's genome impacts iPS cell outcomes  What you eat can influence how you sleep  Brain receptor regulates fat burning in cells Diverse gut microbes increase infection resistance  Zika virus, linked to birth defects, is spreading   Eat fish in pregnancy to improve baby's brain   Turning epigenetic marks OFF!  Cell signal strength turns on early stem cells   Slow stem cell division causes small brain?   Healing muscular dystrophy with CRISPR   Of protein kinases, embryos and cancer  Can having more children slow down aging? Uterine microorganisms may set stage for disease   A mathematical model for animal stripes   Physics attempts to explain why stem cells move  Epigenetic change leads to cerebellum circuitry   Id tags define developing neural circuits   Mechanism for how organs branch found   How to multiply teeth!   Jan 2016