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 intervention.

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 Jul 6, 2015   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 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   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  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 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  Why some older mothers' babies have birth defects  Cerebral palsy – it can be in your genes  Baby formula poses arsenic threat to newborns  The neural basis for 'being in the mood'  Evolving a bigger brain with human DNA  Angelman Syndrome and our Circadian clocks  Reversing effects of obesity on female fertility  Parents who smoke risk diabetes in unborn child  Baby’s own genes can trigger early birth  Growing a brain in 3-D  New protein linked to gestational diabetes  Secrets of how our kidneys develop  Babies understand complex social situations  Gene differences between male and female brains  Stress in pregnancy can affect baby's weight  Turning back aging in cells  Insecticides with pyrethroids linked to ADHD  A gene vital to the central nervous system  Sleep improves infant memory Personalized treatment for intellectual disability?  Things smell good for a reason...  Effects of thyroid disorders on reproductive health  BPA and estradiol affect sperm development  Caesarean delivery may hamper sex life  Turning stem cells into bones, cartilage & stroma  New way to detect genetic errors in IVF embryos?  Blocking GnIH could eliminate stress infertility  Some men only commit when women are scarce  How the rotavirus causes infection in children  How to reverse obesity and diabetes?  More sun means fewer children and grandchildren  Quitting smoking? Women — time quitting to your cycle!  Circadian rhythms regulate skin stem cells?  When DNA gets sent to "time-out"  How a crucial protein aids learning and memory  Exposure to cold 'switches' white fat to brown fat  'Biological clock' may be able to kill cancer cells  Molecular network identified underlying ASD  Enzyme SPPL3 helps activate our immune system  Egg and sperm cells made from human stem cells  High-fat diet in pregnancy harms stem cells in fetus  Genetic mutation cause of ovarian failure  Hormone replacement therapy for younger women?  12 Genes cause rare developmental disorders  Air pollution linked to increased autism risk  Trophoblasts - the first immune cells of pregnancy?  Expectant dads have hormone changes like moms  Context memory function in preterm babies  Cracking the code of brain development   23andMe sketches USA's genetic portrait   When sperm meets egg - FIREWORKS in zinc!  Paxil — antidepressant has a hidden toxicity   Intestinal tract helps control weight Strategy for treating neurofibromatosis type 1   3-D maps reveal genes fold like 'origami'  PCBs may affect fetal brain  Discovered, stem cell code for specific tissue types Scientists identify principal sensor for touch  "Designer" genes correct Muscular Dystrophy  Sperm quality decreases with age  Boys are more likely to be stillborn than girls  Excess protein may trigger schizophrenia  Folic acid before pregnancy reduces SGA babies  Evolutionary controls seen in thousands of genes   Two-cell embryos already "talk" about their future  Women's fertility linked to selenium in diet  Mom's presence changes genes in infant brain  A gene mutation that alters the male fetus  Molecular signal turns on stem cells in brain Finding "lost" languages in the brain  A potential way to restore hearing  Making cells self-renewing The science behind Total Memory Recall   How the male brain is molded  Resetting a woman's biological clock  How cells know which way to go   Human stomach created from pluripotent stem cells  Clues to heart defects in Down Syndrome   Sugars help us differentiate seasons  Prematurity may explain some neurological risks  Constructing embryos from stem cells   Spontaneous genetic errors found to cause autism  Cash register receipts are high in Bisphenol A (BPA)  Fetal BPA exposure increases adult food allergies  Baby cries reveal cocaine exposure in pregnancy Infants pick up social cues from your eyes Down syndrome develops into Alzheimer's A kid’s genes and moms’ risk for rheumatoid arthritis 'Paradigm shift' explains potassium channels Recipe to make bone and cartilage Neurons “fine tune” themselves at gene level Broccoli sprouts show promise in treating autism  PCBs can change thyroid hormone during pregnancy Rett syndrome mice improve with diet Teens exposed to THC may 'waste' immune systems Cancer drug eases mental illness in mice How a gene change causes childhood eye tumors Virus in Utero May Trigger Childhood Diabetes Contaminated water and pregnancy complications  How tissue grows Bad signal to Sonic Hedgehog creates child brain tumors Gene error affects immunity and facial development How to place a chemical tag to control a gene Discovered, an On/Off switch for aging Don’t drink from (warm) plastic bottles!  Improving language before a baby can speak Ear 'hair' cells need precise alignment to work Green neighborhoods mean better birth weights Breast versus bottle feeding Breast milk protects infant from intestinal disorder First international standards for infants/newborns Phthalates heighten risk for childhood asthma Vitamin E critical during first 1,000 days of life  Prenatal alcohol linked to mental health problems   Mechanism may fuel Downs babies in older moms  Infant's diet creates unique immune systems  A molecular motor for human development  Key to making new muscles