The Fetus in the Womb

At a Glance

• SubjectThe Fetus in the Womb
• Artist and contextLeonardo da Vinci (1452–1519) and his Renaissance world
• Periodc. 1511
• ImageThe fetus in the womb, recto.

Contents

1. A body folded into a page
2. Opening the hidden layers
3. The cow within the human uterus
4. What Leonardo understood
5. Where reasoning went wrong
6. A sequence spread across several sheets
7. Drawing as a test, not merely a record
8. Medicine, books and dissection around 1511
9. An intended book that never appeared
10. A compelling image and an unfinished argument

A body folded into a page

The principal fetus occupies the lower half of the recto. Its head bends forwards, the spine curves, and the crossed legs draw tightly towards the torso. The buttocks lie towards the mouth of the uterus: anatomically, a complete breech presentation. An umbilical cord loops around the legs, although its connection with the placenta is not shown. At the left margin Leonardo adds an ovary and associated vessels. ^[2]

The Royal Collection cautions that the posture was based largely on inference. Leonardo may have examined a miscarried fetus and perhaps the body of a woman who had died in childbirth, but no secure record identifies a single dissection as the source of this figure. He was puzzled by the apparent mismatch between a full-term infant and the much smaller non-pregnant uterus seen in a cadaver. On the adjacent RCIN 919101 he compares the two measurements and repeatedly curls the fetus to discover how the larger body could occupy the available space. ^{[1] [2]}

Modern imaging shows that flexion of the head, trunk and limbs is broadly plausible, and a fetus can assume a breech presentation. That does not turn the drawing into a prenatal snapshot. The proportions, surfaces and pose were assembled from incomplete opportunities, memory, observation and reasoning. Its accuracy is selective.

Leonardo's handling of the media reinforces the sense of contained life. Red chalk establishes soft volumes. Curved hatching thickens the surrounding wall and concentrates shadow around the fetus, while fine ink lines distinguish structures. The child appears modelled as a body, whereas the opened membranes behave like analytical layers. Martin Clayton describes the effect as evoking the “coiled potential” of the child, an unusual moment when Leonardo's anatomical objectivity is joined by palpable wonder. ^{[1] [2]}

The image is still a working page. Notes press against drawings. Small diagrams interrupt the reproductive studies. Some marks revise earlier lines rather than hiding them. Its visual power grew from investigation; Leonardo was not choosing between art and anatomy.

Opening the hidden layers

A uterus cannot be shown intact and simultaneously reveal the fetus within it. Leonardo answers by combining views. The outer wall is cut away, membranes open in sequence and selected parts appear in cross-section. Small sketches below the centre imagine the enclosing layers unfurling one after another, like petals. In the principal figure those layers are opened and held apart so their thickness and relation can be compared. ^[2]

This is a constructed demonstration. No single viewpoint during dissection could provide the whole image. Leonardo gathers observations made at different stages and displays them together. The method resembles his studies of machines and buildings: remove a casing, isolate a component, repeat it at another scale and show positions that cannot coexist physically.

At the upper right, enlarged details investigate how projections from two surfaces might interlock. Elsewhere, small sections test whether those structures bulge inwards, outwards or in both directions. Such drawings do more than decorate notes. They turn a verbal problem—how the fetal envelope attaches to the mother—into a visible arrangement that can be inspected and challenged.

The same page includes a geometrical diagram of a weighted sphere on an incline. Clayton reads this as an attempt to explain whether the fetus's relatively heavy head might tip the body towards a head-first position before birth. ^[2] Domenico Laurenza gives the diagram a wider interpretation: it concerns the static balance of a body suspended in fluid and belongs to Leonardo's contemporary habit of comparing the body of an animal with the body of the earth. ^[8] The readings are compatible as possibilities, but neither label was written beside the diagram as a finished explanation.

A further diagram concerns binocular vision, and notes touch on relief in painting and mechanics. Their presence is useful. Leonardo did not maintain a modern separation between obstetrics, optics, statics and art. He assembled problems when a shared geometry or analogy made them productive.

The most important anatomical error is visible around the fetus. Leonardo covers the inner uterine surface with multiple rounded attachments, or cotyledons. That arrangement belongs to the placenta of a cow and other ruminants. A human placenta forms a single discoid organ attached to a limited area of the uterine wall; it is not distributed as many separate placental units.

Leonardo's source can be identified. Around 1508 he dissected a pregnant cow and recorded its two-horned uterus on RCIN 919055. A calf lies in one horn, and the walls carry numerous cotyledons. In his notes he tried to explain how those many attachments could unite into one afterbirth when the uterus contracted. ^[4] The later fetal sheets apply this carefully studied animal structure to a supposedly human setting. ^{[2] [3]}

The transfer was a mistake, but it was not casual fantasy. Human pregnant bodies were difficult to obtain, preservation was poor and dissection quickly altered soft tissue. Comparative anatomy offered repeatable material and a way to fill gaps. Leonardo assumed that mammalian reproductive structures shared one underlying plan, then adjusted for size and species. That assumption sometimes worked: an ox heart could illuminate much of the human heart. In placentation, species difference was decisive.

The error shows the double edge of analogy. A clearly observed bovine feature became more persuasive when Leonardo drew it with spatial precision. The details at upper right even analyse how maternal and fetal cotyledons interdigitate. Exact draftsmanship can faithfully transmit a false identification when the original specimen belongs to another animal.

Medical historians L. Cataldi and V. Fanos argue that limited access to human pregnancy forced Leonardo to supplement human material with extensive animal experience. They also distinguish the mistaken placenta from more accurate observations of vessels and pelvic relations. ^[6] The sheet should therefore be assessed structure by structure. Calling it either astonishingly modern or simply wrong destroys the historical evidence.

What Leonardo understood

Leonardo recognised that the fetus does not breathe air while immersed in fluid. This was not a trivial question in his period. Avicenna's Canon of Medicine, central to medical teaching in Italian universities, had generated extensive commentary on foetal respiration. Leonardo reasoned that ordinary breathing in fluid would cause drowning and that life must therefore be sustained through the mother. ^[5]

The first part is broadly correct: gas exchange before birth occurs through the placenta, while the lungs are fluid-filled and do not perform postnatal air breathing. His broader explanation remained incomplete, but he used the environment depicted on the page to reject a simple transfer of adult respiration into the uterus.

He also paid close attention to the umbilical vessels. In the cow studies he observed vessels branching through the fetal membranes and understood that the infant's vascular system was not a direct continuation of the mother's veins. That separation is an important insight. Modern placental exchange likewise occurs across a barrier rather than through a simple joining of maternal and fetal blood vessels. ^{[4] [6]}

Leonardo did not possess the cellular or circulatory framework needed to explain that exchange. He still had to decide what travelled through the cord, how nourishment reached the liver, what happened to waste and how maternal life animated the child. Correct observation and incorrect physiology could therefore sit in the same paragraph.

The fetus's curved position, the presence of enclosing membranes, the umbilical link and aspects of the uterine vasculature all gave him strong pieces of the problem. His achievement was to make those relationships spatially discussable. The page lets a reader move from whole posture to attachment, then to a magnified interface and a hypothetical force acting on the body.

The fetal group also marks a correction within Leonardo's own work. His earlier female situs had retained the traditional image of a rounded uterus divided into seven cells, a scheme repeated in medieval anatomy and associated with theories about the sex and position of children. In the later reproductive studies he represented one main uterine cavity. That change brought the basic human form closer to observed anatomy even while he placed bovine cotyledons on its wall. Progress was therefore uneven and local: direct study could displace one inherited structure without removing the animal analogy or the older physiology that surrounded it. ^{[2] [7]}

Where reasoning went wrong

Next to the correct statement about breathing, Leonardo writes that the fetus's heart does not beat. That is wrong. A foetal heart circulates blood long before birth. The error follows from his belief that the child was not yet living independently: if its vitality came through the mother, he reasoned, its own heartbeat might be unnecessary. ^{[2] [7]}

He then extends the dependence into natural philosophy. One soul, he suggests, governs mother and child; her desires, fears and pains can be imprinted on the infant, and sudden terror can kill both. Ideas about maternal imagination had a long life in European medicine and culture. Here they are not detached superstition pasted onto an empirical picture. They form part of Leonardo's attempted explanation of bodily connection, revealing where observation could not resolve a metaphysical question. ^{[2] [5]}

Another error concerns urine. On RCIN 919101, Leonardo notices that a heel appears to press near the fetal perineum and imagines that ordinary urination is obstructed. He proposes a passage from the bladder through the umbilicus and cord, combining the real urachus with a false account of fetal waste leaving for the uterus. Monica Azzolini places this proposal in an existing dispute. Galen and Mondino had described separate channels for food and urine; Leonardo and the surgeon Berengario da Carpi argued for one route, although Leonardo still assigned it incompatible functions at different times. ^[5]

The episode is valuable because it shows how he reasoned. A visible posture created a mechanical problem. A known embryonic structure suggested a route. He then made the route perform the function his model required. The chain is intelligible even though the conclusion is false.

His placental error developed in a comparable way. Bovine dissection supplied real cotyledons; the desire for a universal mammalian plan moved them into a human uterus. In each case the page records both the strength and risk of reasoning by analogy.

The verso rarely appears in popular reproductions, yet it changes the character of the object. Notes on generation surround smaller figures. A fetus appears with its cord. Several drawings study the fetal liver, stomach and umbilical vein, shifting attention from the enclosing uterus to changes inside the developing body. Sketches explore an embryo and its membranes; another note concerns light and shade. ^{[1] [7]}

Leonardo was asking about development rather than merely depicting a late-stage fetus. Elsewhere he planned an ordered account beginning with the first formation of the child, following each part through the stages of pregnancy and explaining nourishment. He proposed learning from hens' eggs and urged himself to examine a hatched egg. The programme was never completed, but it widened embryology from a static anatomy to a sequence in time. ^{[5] [7]}

On the verso, changes in organ size become part of that sequence. Laurenza observes that Leonardo drew the early liver as relatively symmetrical, then considered how its left part would diminish as the spleen occupied more room. The interpretation links development, changing weight and the body's balance in fluid. ^[8] It is a striking hypothesis, although Leonardo lacked the serial human specimens necessary to produce a modern developmental account.

Plants entered the comparison as well. In the related RCIN 919103, he likened the umbilical connection of animals to the stalk connecting seed and parent plant. Hazelnuts, pistachios, pods, eggs, cows and women belonged to a search for common processes of generation. ^[2] This broad comparison could reveal functional similarities, but it could also flatten anatomical differences.

Recto and verso thus operate at three scales. The principal image asks how the entire fetus fits and rests. Details ask how fetal and maternal tissues meet. The reverse asks how internal organs form and change. The sheet is less a portrait of pregnancy than a map of unresolved questions.

A sequence spread across several sheets

RCIN 919102 belongs to a compact group rather than standing alone. On RCIN 919101, Leonardo turns a fetus through several views without enclosing it in a fully drawn uterus. That sheet makes the problem of fit explicit: a newborn's length, he notes, is about one braccio, while the uterus observed in a dead woman is only about a quarter of that in its greatest dimension. He uses repeated flexed poses to investigate how expansion and folding could reconcile the apparent contradiction. ^[2]

The same sheet includes proposed muscles around the pelvis and abdomen. Leonardo renders some broad abdominal structures as long, narrow crossing bands and misunderstands their mechanical relation to the pubis. The error is instructive. He was trying to make childbirth and bodily support into problems of opposed forces, but a familiar engineering vocabulary could distort the soft, sheet-like structures he had not resolved by dissection. ^[2]

RCIN 919103 joins fetal studies to drawings of arm rotation. It analyses the biceps and pronator muscles before moving to membranes opened around a smaller fetus. The juxtaposition is not as arbitrary as it first appears. In both subjects Leonardo reduces thickness, isolates attachments and compares states of motion. One set asks how a forearm turns; the other asks how envelopes attach and unfold. His drawing method migrated between parts of the body even when their functions differed. ^{[2] [3]}

Taken together, the three sheets make a progression of questions rather than a narrative of one pregnancy. RCIN 919101 concentrates on bodily fit, position and pelvic mechanics. RCIN 919102 synthesises fetus, uterus, cotyledons and membranes, then pursues organ development on the reverse. RCIN 919103 tests the enclosing layers and their attachments alongside another study of movement. The sequence is conceptual; later mounting and cataloguing do not guarantee that the leaves preserve their original order.

This distinction protects the page from a common visual shortcut. Reproductions sometimes combine figures from the group under the plural title Studies of the Fetus in the Womb. That title is useful for the series, but it can make several physical sheets look like one designed composition. RCIN 919102 alone has its own material history, reverse and arrangement. The other leaves help explain it without becoming missing panels from it.

The accepted English title also uses “fetus” even though the older route says “embryo.” In modern developmental terminology, embryo normally names the earlier stage and fetus the later period after the main body plan has formed. Leonardo's principal curled figure is clearly intended as a relatively advanced child, so fetus is the more precise label. His studies elsewhere extend backwards to embryos and eggs, and the inherited route can remain while the article keeps the stages distinct. ^[7]

Drawing as a test, not merely a record

The cluster reveals that Leonardo did not draw only after reaching a conclusion. Drawing generated questions. When he repeats a flexed body, he can compare the space occupied by different arrangements. When he opens membranes like petals, he can test their order. When he enlarges cotyledons, he can imagine how two tissues interlock. When he reduces a weighted fetus to a sphere on an incline, he can ask whether balance predicts a change in orientation.

Each operation also carries a risk. Repetition can make a guessed pose appear observed. A clean section can imply boundaries softer or less regular in a specimen. An exploded view can separate tissues that function through continuous contact. A geometrical model can turn a biological process into a problem governed by one force. The page's clarity must therefore be read as an argument rather than a photograph.

That is why the small drawings matter as much as the celebrated child. They disclose alternatives, corrections and routes not followed. The large figure gives the inquiry a compelling centre, but the surrounding marks preserve the uncertainty that a finished anatomical plate would usually suppress. Leonardo's visual authority is greatest when the viewer can still see him testing it.

Leonardo's reproductive studies emerged from a crowded intellectual field. Medieval and Renaissance physicians had long debated conception, sex difference, nourishment, respiration, ensoulment and the uterus. Taddeo Alderotti, Tommaso del Garbo, Jacopo da Forlì and Mondino de' Liuzzi belonged to an Italian university tradition that treated the hidden site of generation as a major philosophical and medical problem. Galen and Avicenna supplied authoritative texts whose claims could be interpreted, contested or fitted to new observations. ^[5]

Leonardo knew parts of that world without holding a university medical degree. By the winter of 1510–11 he was probably working at Pavia in proximity to the anatomy professor Marcantonio della Torre. A reminder on RCIN 919102 mentions a book on water for “Messer Marcantonio,” and one passage on fetal membranes may be in another hand. These clues support collaboration, but they do not allow every statement or drawing to be divided securely between the two men. ^{[3] [8]}

Dissection itself was not categorically forbidden by the Church. Italian medical schools staged public dissections, and doctors performed autopsies in certain circumstances. Access, status, season, the supply of unclaimed bodies and the rapid decay of tissue imposed practical limits. ^[3] Pregnant human material was especially rare, helping to explain the dependence on cows and other animals.

The date c. 1511 places the main campaign after Leonardo's intensive work on bones and muscles in Anatomical Manuscript A. The reproductive sheets carry forward its disciplined use of multiple views and sections, but their questions are less easily answered by pulling a tendon or exposing a bone. Some scholars argue that Leonardo added notes to RCIN 919102 during his Roman years, after the main Milanese drawing campaign. ^[8] The page may therefore preserve more than one moment of thought.

Its mixture of empirical and philosophical language was typical of the problem, not evidence that Leonardo suddenly abandoned observation. The fetal body forced him to reason about processes that were hidden, gradual and difficult to reproduce. Drawing became the place where sparse specimens, books and analogy met.

An intended book that never appeared

Leonardo repeatedly planned an illustrated treatise on anatomy. His sheets developed conventions that later seem familiar: sectional views, transparent layers, repeated viewpoints, exploded arrangements and diagrams of force. Had they been ordered, translated from private mirror-written notes and published, they could have made an extraordinary contribution to anatomical illustration. ^[3]

They were not published. After Leonardo's death in 1519, his papers passed to Francesco Melzi. The sculptor and collector Pompeo Leoni later reorganised many drawings into albums, separating them from parts of their original notebook context. An album containing most of the anatomical material entered the Royal Collection by about 1670. The sheets were admired but remained effectively unavailable to medical readers until facsimile publication and translation in the late nineteenth century. ^{[3] [9]}

That history establishes an essential limit. RCIN 919102 did not found modern embryology, guide Renaissance obstetric practice or begin a continuous research tradition. Later anatomists reached their knowledge through other dissections, publications and instruments. The drawing's modern celebrity is an afterlife, not evidence of contemporary influence.

Its historical importance rests elsewhere. Few surviving pages show so clearly how a Renaissance investigator built an explanation when direct access was fragmentary. Leonardo combined a possible human fetus, the placenta of a cow, authoritative medical questions, mechanical diagrams and extraordinary draughtsmanship. The result preserves error in a form precise enough to diagnose.

A compelling image and an unfinished argument

The fetus in the womb remains compelling because it holds several kinds of truth together without resolving them. The folded body is spatially persuasive. The opened membranes demonstrate a powerful method for showing hidden layers. The bovine cotyledons are beautifully described and wrongly assigned. The statement about breathing approaches the physiology of fetal dependence, while the absent heartbeat and shared soul lead away from it.

Leonardo's achievement was not that every conclusion anticipated modern medicine. It was his ability to make difficult questions visible. He asked how a fetus fits, turns, receives nourishment and changes internally; how two vascular systems meet without simply joining; and how a living body can remain immersed before birth. Each question generated a different graphic device.

Both sides of RCIN 919102 should be read as an unfinished argument. The famous recto supplies the memorable synthesis, but the reverse reveals continued analysis and doubt. The page belongs to comparative anatomy, natural philosophy, mechanics and the history of drawing at once. Its errors define the limits of available bodies and inherited concepts; its visual intelligence shows how far one investigator could travel within those limits.

Continue exploring Leonardo

• Leonardo's Anatomical Studies
• Leonardo and Science
• Leonardo and Mathematics

Frequently Asked Questions

References

1. Royal Collection Trust, “The fetus in the womb; sketches and notes on reproduction,” RCIN 919102. View Source
2. Martin Clayton and Ron Philo, Leonardo da Vinci: Anatomist (Royal Collection Trust, 2012), catalogue no. 71. View Source
3. Martin Clayton, “Leonardo's Study of Anatomy,” Royal Collection Trust. View Source
4. Royal Collection Trust, “The uterus of a gravid cow,” RCIN 919055. View Source
5. Monica Azzolini, “Leonardo inside out,” Thinking 3D. View Source
6. L. Cataldi and V. Fanos, “Leonardo da Vinci and his studies on the human fetus and the placenta,” Acta Biomedica 71, supplement 1 (2000), 405–406. View Source
7. E. C. G. A. Fernandes et al., “The Renaissance of Reproductive Science: Leonardo da Vinci's Anatomical Contributions,” Reproductive Sciences (2025). View Source
8. Domenico Laurenza, “Un caso non noto dell'analogia micro-macrocosmica in Leonardo,” Mefisto 5, no. 1 (2021), 75–84. View Source
9. Royal Collection Trust, “Leonardo in the Royal Collection”. View Source

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