The fetal circulation is identical with the venous circulation of the adult male and female

THE FETAL CIRCULATION IS IDENTICAL WITH THE VENOUS CIRCULATION OF THE ADULT MALE AND FEMALE LOUIS DROSIN, M.D. Attending Gynecologist and Obstetrician, Beth David Hospital NEW YORK,

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writers on obstetrics stiI1 express themseIves, when writing on the feta1 circuIation, that it is composed of oxygenated or arteria1 bIood when they essentiaIIy mean suffIcientIy oxygenated bIood, I find it advisabIe to show that the feta1 circuIation during the first three to three and one-haIf months is arteria1 or hyperarteria1 and that it is venous thereafter; that its circuIatory apparatus is constituted with appurtenances to carry on a Iarge scaIe venous circuIation, and that near birth and at birth the circuIation changes to arteria1 and venous variety, and that the venous circuIation is identica1 with the venous circuIation of the aduIt maIe and femaIe. “Certain structures are necessary to the performance of the feta1 circuIation, but are of no use after birth. They are as foIIows: (I) Foramen ovaIe . . . An opening between the two atria. It furnishes direct communication between them. (2) Ductus arteriosus . . . A bIood vesse1 connecting the puImonary artery with the aorta. (3) Ductus venosus . . . A bIood vesse1 connecting the umbiIica1 vein and the inferior vena cava. (4) The pIacenta and the umbiIica1 cord . . . The umbiIica1 cord unites the pIacenta with the nava1 of the chiId. The cord is made up of two arteries and a vein. The arteries are branches of the arteria1 system of the fetus and carry bIood from the fetus to the pIacenta. The usua1 distinction between arteria1 and venous bIood cannot be recognized, as the bIood of the fetus is never up to the arteria1 standard of the mother.“’ “The pIacenta is performing severa vita1 functions of the fetus aImost entireIy. It is the Iungs of the chiId.“2 INCE

YORK

From quotations and from my own observations and views I shaI1 try to show that the circuIating bIood of the fetus is strongIy venous in character with the exception of the first three and one-haIf to four months of gestation which I choose to caI1 the proIiferative or potentia1 stage of the feta1 existence. This stage embraces the period between the time of conception and that of actua1 Iife. The pIacenta during that period of feta1 existence is of a pink appearance, of a veIvety soft consistency; cotyIedons are UndistinguishabIe and when broken up its content of bIood is of a pink hue, simiIar to the color of the pIacenta1 tissue; at times even a hyperarterial bIood can be squeezed out therefrom. The bIood present is not as abundant as in a mature pIacenta. The circuIar sinus is more distinctIy and more compIeteIy formed than in a mature pIacenta and contains free bIood of a consistency and appearance of InnumerabIe fine arteria1 oxygenation. viIIi, finer and more numerous than in a mature pIacenta merge and emerge from its waIIs. Not infrequentIy a pink or soft cotyIedon is seen amidst a mature greyishblue or greyish-bIack pIacenta, a surviva1 of the feta1 proIiferative stage with a bIood content Iess venous than the rest of the pIacenta. I can best iIIustrate this phase of pIacenta1 deveIopment by quoting my own writing: “The frequent presence of immature tissue resembIing in structure and consistency the pIacenta of about two and one-haIf to three and one-half months’ gestation, e.g. soft texture, Iow density, non-caIcareous, infarct free and of a varying pink hue instead of the usua1 purpIe bIue or bIuish green. It occurs as whoIe cotyIedons or as engrafted parts at the

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circumference of any cotyIedon, and occasionaIIy at its center.“3 These facts suggest that the fetus, during the stage of prohferation, before metabolic processes are urged upon it or before the presence of so-caIIed life is manifest, is supphed with fueI of bIood of a nature arteria1 or arteria1 pIus. It also shows that some fetuses require more oxygen than others; or that nature in its wise providence supphes additional means of oxygenation, in certain cases, for future needs. As soon as the metabohc need for its wants is established, corresponding to the functiona deveIopment of the cardiac appurtenances which disappear after birth, the bIood deveIops a carbon dioxide content combined with oxygen and it, as we11 as the pIacenta, becomes more or Iess purpIe or venous. Period from End of the Proliferative Stage to Beginning and through Metabolic Stage to End of Labor. Inspection of the retro-

pIacenta1 bIood of the mature or near mature pIacenta shows that the cIots are, as a ruIe, venous in nature mingled with clots of coIors arteria1, and aIso free brood combinations of unmixed and partly mixed arteria1 and venous bIood, or either entireIy venous or entirely arteria1. This arteria1 bIood points to nature’s effort to suppIy an increased amount of oxygen, when necessary, during labor. At the same time I am not unmindfu1 of the fact that the pureIy arteria1 bIood or at Ieast part of it, undoubtedly comes from the uterine waI1 after separation of the pIacenta or from a deep Iaceration of the cervix before the uterus has contracted, or from both sources, before the dehvery of the pIacenta has taken pIace. The varying cIots and the differing shades of mixed and free venous bIood most definitely emanates from the pIacenta1 cotyledons as a resuIt of breaks in continuity caused by pressure and counterpressure exerted on them during the second and third stages of Iabor. After the cord is doubIy cIamped and cut, remove the dista1 cIamp and Iet some of the bIood ffow on the white draping; then remove the cIamp from the proxima1 or

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feta1 end and repeat the same thing near the first stain and both stains wiII Iook After the chiId has identicahy venous. visibIy breathed a few times and before the bIood in the feta1 stump has coaguIated, remove the cIamp again and Iet some of the bIood fIow on the draping cIose to the previous stain, and this Iast stain wiII be bright arteria1 biood. Further observations on the mature placenta emphasizing the venous nature of the feta1 circuIation. Cut across a Iarge vein on the feta1 surface of the pIacenta and there wiII ensue a sudden copious ffow of venous blood. Now, cut across a comparativeIy Iarge artery and a reIativeIy minute quantity of simiIar or higher grade venous bIood wiII come forth. AIso, hoId the cord in an upright position and cut away the cIamped end. ImmediateIy there wiII issue a spurt of venous blood. Milk up the bIood in the cord, starting at the pIacenta1 end unti1 a11 the bIood is squeezed out. InstantIy the cord spontaneousIy and visibIy rehhs. Squeeze out a11 the bIood again and again and the same thing wiII happen. CIamp the umbiIica1 vein at the side of the cord or at its outlet and miIk up the cord and you wiII get a few minute quantities of strongIy venous bIood from two or occasionaIIy three pinhead arteriaI openings; and after a few milkings nothing wiII come forth. Now, uncIamp the umbihcal vein and miIk the cord again. You wiII again obtain the same quantity and degree of venous bIood as before; miIk the cord repeatedIy and the same degree of venous bIood wilI continue to flow. You wiI1, however, obtain no more bIood from the umbiIica1 arteries. These facts indicate that the venous circulation is activeIy upstream whiIe the arteria1 is passiveIy downward. “At caesarian sections, through intact membranes, the baby appears bIuish and Eastman’s studies show that at birth it is normaIIy cyanotic.“2 COMMENT

AI1 fetuses delivered as miscarriages and al1 fetuses during cesarean deIivery before

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the membranes are ruptured, are cyanotic; which again shows that the feta1 circuIation before it is in contact with atmosphere is strongIy venous. Soon after the membranes have ruptured or immediateIy after deIivery when the fetus is in contact with the atmosphere and its pressure, it quickIy becomes Iess venous even before it has visibIy breathed. The difference between intrauterine pressure is so great and the feta1 body so yieIding that air wiI1 be forced into the nostriIs and mouth, stimuIating the Iarynx; and through the pores of the skin which is the beginning of cutaneous respiration. This can be borne out by the fact that inspection of the chest and abdomen, just before the first gasp of respiration or the first cry, wiII show tiny, rapid movements of inspiration and expiration. They are best observed on apneic chiIdren. In a norma chiId, normaIIy born, before the cord is tied and before it has actuaIIy breathed, if its abdominothoracic region is pIaced on the paIm of the hand, it wiI1 assume a position of hyperextension-rotation, that is, instead of flexion or ffexibiIity it becomes tenseIy hyperextended and in rotation to right or Ieft through an arc ranging from 180 to 250 degrees. When I had first described this phenomenon’ I attributed it to the forces of Iabor imposing, impressing or transmitting a continuation of direction on the fetus to the period immediateIy postpartum. I now wish to add to this theory that it is aIso due to reaction of atmospheric pressure and the effects of the same. To a Iess degree this phenomenon can aIso be observed when the chiId is pIaced with its back on the mother’s abdomen. It wiI1 be observed that the chiId’s extremities are raised in a tenseIy rigid position with tendency of the spine to hyperextension. This extension-rotation usuaIIy Iasts from a quarter to threequarter minutes, when the chiId takes a deep gasping breath, reIaxes and cries IustiIy. Estimates of as high as 50 per cent of oxygenated bIood in the umbiIica1 vein as compared with the arteria1 of g5 per cent2

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are not a standard, as it is Iess and stiI1 Iess, as an increased amount of oxygen has aIready been forced into its circuIation and its tissues by the powerfu1 contractions of Iabor, and has come in contact with atmospheric pressure even whiIe issuing through the vuIva and has breathed aIready partiaIIy or compIeteIy. These facts influence the estimates as they are invariably done after the chiId is delivered. The pIacenta1 and umbiIica1 veins carry sIightIy oxygenated bIood to the feta1 heart and tissues and after having given up their oxygen the arteries carry back pureIy venous or deoxygenated bIood. “The fetus in utero is hypotonic if not actuaIIy atonic. It Iacks we11 deveIoped mechanism to return its bIood to the heart. The uterine muscuIature substitutes for this Iack of tonus and rhythmic preIabor uterine activity assists in returning the bIood to the feta1 heart.“2 The feta1 heart then acts simpIy as a reIay station on the highway of the feta1 circulation; it is acted upon purposefully instead of acting on its own initiative. To be more specific, the feta1 heart beats not because it circuIates bIood but because, essentiaIIy, bIood is circuIated through it; or bIood is pumped through the feta1 heart instead of the heart pumping the bIood. “The fetus needs IittIe oxygen as its combustion processes are SIOW; it moves IittIe and meets with no resistance; it has no perspiration with the evaporation from the skin. It Ioses no heat.“2 The change from the nata venous circuIation to the postnatal arteriovenous circuIation is approximateIy as foIIows : The first and most important event is the onset of respiration. The effect on the newborn of the sudden change from intraabdomina1 to atmospheric pressure with the resuIting respiration I have aIready mentioned. In the aduIt the vacuum circulatory system is in cIose co6rdination with the respiratory vacuum mechanism where each one is auxiIiary to the other and each one is pacemaker or equiIibrator to the other. The initiaI start in that direction is accompIished by the stoppage of the pIacenta1

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From this moment on the circuration. child has need for more oxygen and hence gets the urge to seek its own oxygen suppIy. “AI1 the primary readjustments appear to be fairIy we11 accomphshed by the end of the first month or six weeks after birth. The Iungs are compIeteIy inflated, the red ceI1 count and the hemogIobin index are about at aduIt IeveIs, the Iumen of the ductus arteriosus is reduced to aImost nothing, and the vaIvuIa foraminis ovaIis has been puIIed tight across the foramen and cIose against the septum.“* “Last of a11 the postnata1 changes to be accomplished is the buiIding up of the left ventricuIar muscuIature. The factors which initiate the increase in weight and the power of the Ieft ventricuIar waI1 becomes operative when the new functiona baIance is estabIished in the heart with the actua1 cIosure of the ductus arteriosus and the functiona cIosure of the foramen ovaIe.“l Nature does not toIerate vacuums and the whoIe system of circuIation and some of its purposes is the tendency to vacuum formation and its prevention. The driving force and highest source of feta1 circuIation is the materna1 heart whose bIood is ampIy accumulated and reIayed through the uteropIacenta1 subsidiaries to the feta1 heart, and returns by means of the arteries through sheer gravity back to the uteroplacenta. This gravitationa flow downward creates a tendency to vacuum formation above it, and the tendency to prevent such vacuum formation stimuIates an upward venous flow. This process goes on continuaI1y. The fact that the source which gives the impetus and power to the feta1 circuIation, the materna1 heart, is higher than the fetus, adds momentum to the feta1 circuIation. The caIiber of the momentum is so constituted that it can reverse the direction of the feta1 circuIation, as in cephaiic presentation, with equa1 faciIity, in fact with superior faciIity, as the direction of the circuIation is down instead of upward. This is due to the hypotonicity or atonicity of the fetus. In the aduIt maIe and femaIe the gravi-

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tationa1 downward flow of arteria1 bIood minus resistance of venous-Iike vaIves, backed by the siphoning contraction of the heart is power[uI enough to stimuIate and start the venous circuIation upward, assisted by respiration. These facts make the passive venous circuration so rapid, and its audibIe puIse rate is caused by its hitting the fIaps of the venous vaIves. In the fetus the venous sounds are cornpIemented by the action of the atonic heart. The venous circuIation of the aduIt as we11 as of the feta1 heart is of irreguIarIy aiternating double and single beats.:’ I shouId attempt to expIain this on the assumption that the venous valves do permit a certain refIux ffow when the quantity needed is super- or subabundant temporariIy; and this may happen at any moment in any part of the body. Since the fetus is hypotonic or atonic, the same status must apply to the heart which is being acted upon; the same refIux is undoubtedIy taking pIace therefrom. As the oxygen or the oxygen and carbon dioxide suppIy is not uniform, the same thing appIies to the bIood suppIy and there has to be periodic excesses or diminutions of the same and hence there must be regurgitation. The feta1 heart is equipped with appurtenances which disappear after birth to enabIe such regurgitation without the incidence of murmurs. The unstabiIity of the feta1 circuIation is evidentIy due to the atonicity of the fetal heart and to the fact that the vasoconstrictor and vasodiIator system of contro1 is stiI1 absent or undeveIoped in the hypo- or atonic fetus. AIthough the maternal and fetal circuIations are in a sense, independent, nevertheIess the feta1 circuIation emanates from the system of the materna1 circuIation. The fetus having origin in adults and being a potentia1 aduIt, must have its scheme of behavior and its way of Iife expIicitIy imposed on it. The Iarger system of venous circuIation than that of the arteria1 which is essentia1, and which both the adult and fetus aIike possess, the more yielding waIIs of the veins as compared

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with the arteries which make them more responsive in resisting vacuum formation, and the fact that the veins have vaIves preventing undue reff ux, and the siphoning action of the heart in the ad& are important agencies for the execution of the vacuum based feta1 circuIation. As the pIacenta is the Iungs of the fetus, the contractions of the uterus with their actions on the pIacenta are its oxygen suppIy as we11 as the reservoir suppIy of bIood of the uterine and pIacenta1 sinuses and the muItipIicity in numbers and reIative Iargeness of the pIacenta1 veins. They form a superabundance of oxygenated bIood to maintain the fetus in the stage of its vast proIiferation activity and Iater these very channeIs suppIy a mixture of oxygen and carbon dioxide sufficient to carry on its Iimited metaboIic processes required for its Iimited functions. To faciIitate the venous circuIation “the viIIi grow in the direction of the venous openings and away from the arteries, the bIood stream naturaIIy swimming then m authis direction.“2 The vacua-aspirating tomotive action of the circuIation and principaIIy of the feta1 circuIation is compIemented and faciIitated by a vermiform action of the uterine muscuIature not unIike that of the unduIating waves of the stomach or the undulation of the scrotum, the Iatter vividIy visibIe to the naked eye. The arrangements of the muscuIar Iayers of the uterus is just suitabIe for such vermiform action cuIminating in the painIess uterine contractions of the non-gravid and the gravid state and the painfu1 contractions of Iabor. Since there are periodic contractions of the uterus there has to be preIiminary or preparatory steps Iike the unduIating movements, Ieading up to these climaxes which in turn subside to the various degrees of unduIation. Crux of the Thesis. The aduIt venous puIsations, identica1 with that of the feta1 heart working through venous channeIs, can be heard in men and women and youths over parts of the body where its circuIation cannot be compressed by the stethoscope.

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It is best heard at and on the anterior superior spine of the iIium, the iliac fossa, the IumbosacraI region, the symphysis pubis, the coccyx and over the Iong bones, more so over the Iotier extremities, aIso over Poupart’s Iigaments, fibroid uterus and pregnant uterus, particuIarIy before the feta1 heart beats are audible. The venous sounds and rate are typica of the feta1 heart with the exception that they are of a Iower pitch. It may take a onequarter to one-haIf minute for the transition to take pIace from the sIower and higher pitched radia1 puIse rate to the rapid, irreguIarIy aIternating singIe and doubIe Iow pitched venous puIsations to be heard. In most instances both the arteria1 be heard and venous puIse rates can synchronousIy.6 SUMMARY

AND

CONCLUSION

I. There is a stage of feta1 existence, the proIiferative stage, before active Iife has set in, when the fetus is suppIied with arteria1 bIood. 2. The estimates of oxygen in the feta1 bIood is done after deIivery when it has acquired additiona oxygen through uterine contractions of Iabor, atmospheric pressure and actua1 respiration. 3. Because the feta1 body and consequentIy the feta1 heart is atonic or hypotonic, and not subject to the vasoconstrictor and vasodiIator influence or but sIightIy so, it does not pump bIood but bIood is pumped through it. 4. The feta1 circuIation is initiated, stimuIated and carried on by the materna1 heart and reIayed by way of the uterine contractions, uterine muscIe activity, pIacenta circuIation and fetal heart. 5. The feta1 veins and heart permit refI ux of bIood without incidence of murmurs. 6. The uterus possesses an unduIating mechanism which cIimaxes into uterine contraction, again receding to unduIations. 7. The feta1 bIood suppIy may be divided, as far as its oxygen suppIy is concerned into a triad of (I) proIiferation or potentia1 life, with arteria1 circuIation,

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(2) venous circuIation during active Iife and (3) combined arteria1 and venous circuIation during the stage of Iabor to counteract the increased content of carbon dioxide. 8. The source of retropIacenta1 cIots and free bIood and the cause for the various states of oxygenation are pointed out. g. A method of eIiciting venous circuIation in aduIts is expIained. I o. The feta1 circuIation is IargeIy stimuIated by a tendency to vacuum formation and its prevention. In aduIts the vacuum circuIatory mechanism is suppIemented by the expiratory tendency to vacuum formation and its prevention and they both form an equation: one is to the other as the other is to the one. I I. The independent circuIation in the newborn is initiated by the stoppage of the pIacenta1 circuIation causing an urge in the fetus to seek its own oxygen suppIy. It finds this urge gratified by atmospheric pressure forcing air into the Iarynx and through the skin when the feta1 body is reIeased from pressure and compression of Iabor; and together with the change of temperature (higher or Iower) they all cuIminate into the system of respiration. 12. The feta1 circuIation with its rate about twice that of the mother’s is identica1 with the venous circuIation of the aduIt maIe and femaIe. 13. WhiIe the venous circuIation is of a Iow pitch, the feta1 heart sounds, identica1 with it, are of a more intense nature

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and of a higher pitch as a resuIt of the additiona sounds caused by systoIe and diastoIe. I 4. The extension-rotation reaction of the fetus to atmospheric pressure is, as a ruIe, the first visibIe evidence of extrauterine Iife. It is aIso the first instance of extrauterine vacuum presence and the inspiratory tendency to counteract it. 15. The aduIt heart beats are about onehaIf the rate of the venous circuIation due to the rhythmic action of respiration, increased bIood pressure, absence of feta1 heart appurtenances, acquisition of muscuIar size and tonicity of the same, together with the vasoconstrictor and diIator system of control. REFERENCES

I. KIMBER, DIANA CLIFFORD, GRAY, CAROLYN E. and STACKPOLE,CAROLYNE E. Text book of Anatomv i and PhysidIogy. Pp. 313-315. New York, 1934. The MacmiIIan Company. 2. DELEE-GREENHILL. The PrincipIes and Practice of Obstetrics. 8th ed., chap. 3, p. 48. PhiIadeIphia, 1943. A’. B. Saunders Company. 3. DROSIN, Louis. Placenta1 attachment and separation as influenced by vacuum action, equilibrating force and retropIacenta1 bIood. Am. J. .%Y., 33: 52. 1935. 4. CURTIS, ARTHUR HALE. Obstetrics and Gynecology. VoI. I, p. gzf. PhiIadeIphia and London, 1934. W. B. Saunders Co. 3. DROSIN, LOUIS. EIicitation and significance of abdominal sounds during pregnancy and labor. Med. Times, February, 1925. 6. DROSIN, LOUIS. The venous circulation is audibIe throughout the system; it is also audibIe in fibroid uteri. Received for DubIication. (To be oubIished.l 7. DROSIN, LOUIS. Rotation extension of the fetus postpartum. Med. Rec., December 6, 1939. I

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