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  Apr 2016   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? Mar 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  Feb 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  Jan 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!   Dec 2015   Increasing IVF cycles increases chances for live birth   Make impulsive choices? Blame mom and dad's genes   Multilingual babies use more cognitive control   How genes link heart and neurodevelopmental disease   Messenger RNA may fine tune protein production   A major step toward growing kidneys   Sperm pass on information about dad's weight   Sperm 'see' it hot   Human stem cells likely safe for use in regenerative medicine   Turning point in a lifetime   Antidepressants increase autism risk 87 percent   A subtle dance of atoms influences enzymes   Molecule stops brain stem cells from becoming tumors   Sleep may strengthen our immune system   Neuroscientists now can read the mind of a fly   CBD in cannabis shows promise for severe epilepsy   Four studies explore memory decline with epilepsy   'App' may improve daily function in schizophrenia   Hippocampus essential in all aspects of recognition memory   Working memory is more complex than we thought  The silence of the genes  Cells 'reach out' to build trachea   How cells in the developing ear 'practice' hearing Nov 2015   Correcting gene error restores brain function   Babies have logical reasoning before age one   How cells begin to shape a living being   Target gene identified to combat muscular dystrophy   Turning taste on and off in the brain   A master switch for brain development?   Targeting Alzheimer's disease through anti-aging   Repairing neurons with light   Our brain, more than chimp's, influenced by epigenetics   Do metabolites regulate embryo development?    Working on toddler's memory can help in high school   Batten disease may benefit from gene therapy   Prenatal blood test increases accuracy - reduces risk   A way to target Neuroblastoma   What happens if DNA cannot fit into the nucleus?   Why some genes are frequently read more than others   High stress in pregnancy may decrease baby's survival   More precise due dates for average pregnancy?   Can amniotic fluid predict time of delivery?   Singing calms baby longer than talking   Common preservative may increase breast cancer  Oct 2015 Antibiotics in children promote weight gain    Mom's preeclampsia increases risk to baby's heart   The mighty Panoramix — defender of genomes!   Splitting embryo to force twins for IVF - not advised   Dad's microRNA affects his baby's brain   How RNA regulates sex-linked disorders   Htt protein controls Rab direction on neurons   Regrow a tooth? Fish, yes! Humans, maybe ...   Sleep as reward boosts learning   Extra male brain cells remember sex more than food   Generating placental cells from skin cells   The father effect   Chromosome errors may explain brain birth defects   Gene links chromosome errors to early pregnancy loss   A gene that prevents Parkinson's disease and dementia   Ovarian transplants appear to be safe and effective   Restoring vision using pluripotent stem cells    Artificial Intelligence helps predict cancer   OB-GYN group urges prevention of chemical exposures   Global warming lowers birth weights   Kids being kids — make better parents   A hormone to break the obesity cycle?   Sep 2015   Pass the salt — How pregnancy drives food cravings   Mom's protein deficiency affects boys more   Do chemicals make us couch potatoes?   New CRISPR-Cas9 strategy edits genes 2 ways   Depression gene has a silver lining   Grieving before conception — risk to infant?   Decoding cell division   Two genes play major role in growth and cancers   The grandmother hypothesis   The black box at the beginning of life   A new method to turn genes off and on   New molecule found to prevent preterm birth   What steers evolution? Genes, then nature, then genes..   3-D printed organoids - first step to building organs   Come here, and be quiet!   How neurons branch   Childhood Vaccination Reduces Leukemia Risk   Fats help organize spinal cord    'Brainbow' reveals a surprising visual connection   Obesity and stillbirth  Arsenic in drinking water links early puberty and obesity   Do sperm wield tiny harpoons?  Aug 2015   Building a safer stem cell   How zebrafish rebuild their amputated fins   Batting practice in the genome   Algorithm identifies gene movement around the clock    About that Paleo diet, eat some carbs!   Infertility of middle-aged mice can be reversed   Pre-pregnancy factors affect two generations   Engineering a solution to genetic diseases   Ultrasound has potential to detect preterm labor   One protein keeps cells both static and moving!   What controls our waking up and going to sleep?   How can labor contractions keep growing stronger?  Resurrecting ancient viruses to improve gene therapy   Skin stem cells coaxed to become Schwann cells    How a single genetic mutation can cause autism   Surprising light on genetic causes for cerebral palsy   Drinking at conception boosts diabetes risk for baby   Altered brain growth in autism spectrum disorder    Stem cells one step closer to curing genetic disease    Simple flip of a genetic switch begins aging   Stressed birds stop looking to parents, turn to flock   July 2015  'Miniature brains' from skin cells explain autism Birth order not meaningful to personality or IQ   Genetic roots of scoliosis   Reverse hearing loss?   Mind the gap!  Bad genes don't always lead to same outcomes  How is temperature affecting mammal moms?  Sialic acid is key to unlocking brain disorders   Metformin does not reduce baby birthweights  Binge-eating cavefish share gene mutation with us   Hippo dances to hormones  How good is your eyesight? CEP63 Gene key to brain development and fertility  Geometry of brain’s surface matches gene heritage 'Avandia' to be clinically tested for preeclampsia  Determining the front and back of a cell  Long-term memory maintained by prion-like proteins  Autism affects neural pathways and brain shape Fine tuning the brain  REM sleep critical to young brain development   Brain size/intelligence controlled by a single gene   Stressed moms alter babys' gut and brain   Placenta-on-a-chip    June 2015  Educate mom, reduce unintended pregnancies  Picky eaters — a serious problem for some New Noninvasive and effective Prenatal Testing Strong working memory can reduce teen sex?   Gene mutation triggers lymphoblastic leukemia  Sun's coronal gases may harm our health  Cat videos make you 'feel-good' and boost energy!  Humans, we may have a built-in GPS in our nose  Low glycemic index diet reduces autism symptoms   Common pesticide linked to ADHD — in boys  Artificial intelligence regenerates planaria  Egg or sperm? That is the question...  Mutations can spontaneously occur in early embryos  Progeria syndrome truly a disease of aging  Infant brains develop faster than we thought  The Secret to a Longer Life? Be Female   Motherhood permanently alters your brain  Genes can predict a woman's first birth  Genetic mutation link to autism might be undone  Why and how to barcode thousands of cells  Clues to how human neurovascular unit forms    Mothers coo while fathers say cool   May 2015  Supplement may prevent alcohol-related defects  Alcohol damage before mom knows of pregnancy  Hydrogels boost stem cells to heal brains  Mom's obesity compromises infant immune system  Risk of preterm delivery for women born preterm Acetaminophen can lower testosterone in fetal boys  DNA reveals impact of malnutrition on fetus  Taking immortality out of cancer  Genome editing could cure sickle cell anemia  Brain cells are capable of switching "careers"  C-section knocks out infant gut microbiome   Placenta protects baby with transporter proteins  Shedding new light on reproductive disorders  How our brain plugs in vision stabilization  How to stop "jumping genes" in stem cells  Parent training reduces autism behavioral problems  Replace 1 sugar drink a day - cut risk of diabetes  Engineering new blood vessels is closer to reality  Cell mitochondria are key to stem cell development  How come we are warm-blooded?  Most People Carry Recessive Disease Mutations   April 2015  Link between physical forces and limb deformities  Genetics behind fetal overgrowth syndrome found  Mitochondrial genes and disease inheritance How young cells learn to communicate How oxytocin makes a mom  Stem cell based birth defect can repair facial bones   How zinc deficiency affects embryo and adults  Found — proteins critical for DNA repair   Breast cancer and the fountain of youth  Newborn brain is altered by mom's use of cocaine Dad's sperm may hold clues to autism  How electrical charges move through DNA  When using our brain muddles solving a problem  Autism's early 'neighborhood'  Food allergies can be transmitted through blood  A method for blocking pregnancy loss?  Why we are becoming myopic  How do lifeforms know how to be the right size?  New clues on origin of Hirschsprung's disease   About Congenital Diaphragmatic Hernia  Some birth defects due to shattered chromosomes  March 2015 Why we need to make neurons from stem cells  A link between autism and higher intelligence  Solving the "obstetrical dilemma"  Inducing pluripotent stem cells to reprogram  Radical vaccine against herpes viruses  Leukemia cells changed into harmless immune cells  Infant leukemia results from one rearranged gene  Mom's age at childbirth affects boy baby as adult   How dieting and fasting turn off inflammation  A mutation that can cause male infertility   How to build a gene location APP  Bioelectricity key in brain development and repair  Low Omega-3 and Vitamin D affects brain serotonin  DNA-binding protein critical to normal embryo  Developing a sense of taste  Mechanical stress is key in cell to cell fusion  New hormone mimics the effects of exercise  Detecting mutations in IVF embryos  Master switch' error causes CHOPS syndrome  Epigenome orchestrates embryo development   Tobacco smoke and preemies with lung disease  Exercise ball decreases labor time and C-sections