A single mummified fetus

Keywords: mummy, mummified, fetus, equine

Mummification of a single conceptus estimated to be about 120 days of age at the time of its death. 

Image size: 900 x 527px  Copyright unknown.

In the absence of luteal tissue, a single mummified conceptus is theoretically unlikely to remain in utero because a placenta is required to maintain pregnancy after accessory corpora lutea have undergone luteolysis (about day 160 of gestation). It was not known if the mare pregnant with this fetus had any luteal tissue in her ovaries. 

References:

Allen W.R. 2001 Fetomaternal interactions and influences during equine pregnancy Reproduction 121: 513–527

Holtan D.W. et al. 1975. Plasma Progestins in Pregnant, Postpartum and Cycling Mares. J. Anim. Sci 40: 251-260

Fetal maceration.

Keywords: fetus, maceration, bones, equine, prolonged gestation

Image size: 769 x647 px

An old but unique image of equine fetal maceration. The fetus was discovered during a rectal examination after a complaint of prolonged gestation. The size of its bones suggest that the fetus was in late gestation when it died.  As occurs in cases of pyometra, this mare showed no systemic signs of disease.

Treatment included tranquillization, followed by manual dilation of the cervix,  over a period of approximately 20 minutes.  When the cervix had been sufficiently dilated to admit a hand, the bones and debris were extracted and the uterus was flushed with saline and antibiotics. Oxytocin treatment followed flushing.

It is not known if this mare maintained her fertility.

 A mesenteric tear as a cause of dystocia

 Keywords: dystocia. equine, mesentry, tear

A Belgium draft mare was referred to our clinic several hours after the onset of second stage parturition. Attempts by the rDVM to deliver the foal had been unsuccessful.

During per rectal examination to ascertain the presence of possible uterine torsion, the foal was not palpable yet one could easily palpate the foal via per vagina examination. This led to some confusion and speculation on the part of the author. Amid this discussion, the owners elected to euthanize the mare.

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On postmortem examination, a large rent was discovered in the mesentery. The large bowel and mesenteric rent is shown above. The location of the body of the uterus and fetus was simulated by the author. The smooth margins of the rent have not been re-touched in this image; they were exactly as shown here.

Evidently, the mesenteric rent had occurred some time before the mare had become pregnant or during early pregnancy, allowing the uterus and part of the mesometrium to pass through this opening. The foal had developed to term, cranial to the opening.  This explained why the foal could not be palpated per rectum yet was easily palpable per vagina. During per vagina examination, the author's arm had passed into the uterus, through the opening in the mesentery. During per rectal examination however, the large bowel lay between the rectum and uterus, disguising the presence of the fetus.

It was not possible for the foal to be born because it had been constrained by the hole in the mesentery. A unique case.

Immature (dysmature or premature) Jennet

Keywords: donkey, fetus, premature, equine

Jennys (also spelled "Jennet" from French, but pronounced Jenny) have gestations that are somewhat longer than those in mares. As in mares, gestation length is highly variable but in donkeys it can be as long as 14 months.

This donkey was born dead, in a slightly immature state.

Image size: 1800 x 1213px

If the gestational age can be shown to be significantly shorter than the mean for the species, the condition is correctly referred to as "prematurity". However, if the gestation length is consistent for that species yet the neonate still appears to be immature, the correct term for the condition is "dysmaturity". Because the breeding date was not available it was not possible to determine if this fetus was  dysmature.

The signs of immaturity in this foal are indicated by arrows or circles and include its soft, floppy ears, a downy hair coat and its flaccid joints in the distal extremities, allowing hyperextension at the fetlock joints. In equids, the testicles have usually descended by birth. In this cases however, the testicles were still within the inguinal canal, the scrotum being filled predominantly by the gubernaculum.

Note: the image also shows the amnion with both intra- and extra-amnionic sections of the umbilical cord

Genital tubercles, genitalia and gonads in fetal sexing

Keywords: fetus, sexing, ultrasound, male, equine

There are many reasons to determine fetal gender in horses. These include a multitude of personal decisions by owners such as preferences for stud Thoroughbred colts, the wish to retain fillies for breeding, insurance concerns, a need for female polo ponies, male draft horses and so on.

Detection and examination of the genital tubercles

First, a note on accurate age determination of an equine fetus. In general stud practice, determination of the exact duration of pregnancy is not possible. Mares are commonly examined at two day intervals or over weekend at three day intervals. When a CH is first detected, it is impossible determine its age. Therefore ovulation could have occurred shortly before one's examination or close to two or three days earlier. If one assumes a two day interval between examinations and pregnancy is timed from when the follicle was last seen, a "55 day pregnancy" could be 53 to 55 days old. If the duration of pregnancy is timed from when a CH is first seen, the pregnancy could be 55 to 57 days old. This seemingly trivial point takes on critical importance when a mare is found to be pregnant with twins at "15 days" of gestation!

It is only when frozen semen is used, that the approximate time of ovulation (and the age of the fetus) is known. Even when embryo transfer is used, the exact age of the fetus is not known. Therefore all the fetal ages in this discussion must be regarded as approximate.

Early sex determination is usually done by transrectal ultrasonography, between 59 and 68 days of gestation by detecting the genital tubercle. The genital tubercle is the precursor of the penis in the male and the clitoris in the female. Around day 55 gestation it appears as a hyperechoic equal sign (=) located between the fetal hindlimbs, at an approximately equal distance between the tail and the umbilicus. As the fetus grows the relative position of the tubercle changes, becoming closer to the tail in the female and the umbilicus in the male.

The image below shows a 64 day male fetus still in its amnion. The arrow indicates the position of the genital tubercle (arrow) used for sex determination. It is highly echogenic and usually easy to locate, just caudal to the umbilical cord. In females, the genital tubercle is located under the tail i.e. in the position of the vulva in a neonate.

In this case, the remnants of the yolk (YS) can be seen, consistent with this stage of gestation.

Image size: 1000 x 717px.

The image below shows the genital tubercles (green rings) of twin fetuses aborted at approximately 60 days of gestation. The upper fetus is male, the lower one female.

Image size: 1000 x 744px. 

Detection and examination of the external genitalia, mammary glands and gonads.

A wide diagnostic window for gender determination exists between 100 and 260 days gestation. During this time, the external genitalia, mammary glands and fetal gonads themselves are examined. and multiple parameters to validate diagnosis (fetal primary sex organs), but may require a combination of trans-rectal and trans-abdominal ultrasound scanning.

The external genitalia of the fetus may be clearly identified on ultrasound as early as 100 days gestation. In the male fetus, a fully comprehensive gender diagnosis includes the identification of the penis, prepuce scrotum/testicular compartments urethra and gonads. In the female fetus, the vulva and clitoris, mammary gland, nipples and again, the gonads themselves.

In the 150 day old male fetus below, the scrotum and penis are well formed but the testicles have not yet descended into the scrotum. Each enlargement seen within the scrotum in this fetus is due to the gubernaculum, not the testicle.  This explains why the scrotal contents are relatively anechogenic  during fetal sexing (see the image below this one).

Image size: 1000 x 757px. 5 x 3.285 inches 200dpi.

In this transabdominal ultrasonograph, captured at seven  months of gestation, the anechogenic contents of the scrotum and the penis are clearly visible. Note the relatively anechogenic scrotal contents.  The penis itself is not visible here because it runs on a plane that is dorsal to the urethra and scrotum.

Image size: 820 x 614px  Author and copyright. Dr Stephanie Bucca: Doha, Qatar. stefbucca@gmail.com

At four to seven months in gestation, the vulva lips, mammary gland and teats can be used to identify a female fetus.

Image size: 2050 x 1612px  Author and copyright. Dr Stephanie Bucca : Doha, Qatar. stefbucca@gmail.com

In image A, the base of the fetal tail is visible with faint cross sections of some of the coccygeal vertebrae seen to the left of the tail base. Between the buttocks of the fetus one can see its anus, vulva lips and clitoris.

In image B, at just under five months of gestation, this fetus is in posterior presentation showing one half of the mammary gland and its nipple. One  hind limb is extended, with the femur shown in cross section. Vernix is clearly visible in the amnion but not the allantois.

In image C, the fetus is in transverse dorsal presentation. Between its buttocks, the anus and vulva lips of the fetus are clearly visible. Essentially, this is the same view as in image A, but closer to the fetus

After about eight months or nine months of gestation, transabdominal ultrasonography for sexing is less predictable than earlier. Although the fetus becomes fixed in cranial longitudinal presentation, its hind quarters are encased in the pregnant horn and may be raised towards the ovaries. (The hind legs are often palpable per rectum in late gestation). In fact, at this time, fetal cardiac examination can be more fruitful than attempts to examine their genitals. Even with low frequency ultrasound, penetration may not be sufficient to examine genital areas of diagnostic interest.

Although male and female fetal gonads have a similar macroscopic appearance, they differ remarkably on ultrasonography, especially when examined by doppler flow ultrasonography.

On the right side of this image, the tunica albuginea and the clear demarcation between cortex and medulla is obvious. The medulla is peripheral to the cortex in equids (a quirk of embryology) and because of its blood supply, it is less echogenic than the cortex. The donut-like appearance of the fetal ovary is very different to the relatively homogeneous appearance of the fetal testicle (see the following image). This forms the basis for accurate sexing of equine fetuses. Approximate time windows for these examinations are between 4 and 5 months transrectally and 7 and 8 months transabdominally.

Image size: 2050 x 1612px  Author and copyright. Dr Stephanie Bucca: Doha, Qatar. stefbucca@gmail.co

When doppler flow ultrasonography is used, the accuracy of gender determination is close to 100% accurate. This because the medulla of the ovary is well vascularized, making it an ideal target for doppler flow examination. The value of doppler flow ultrasonography is easily appreciated in the image above (the scale is the same for both sub-images).

In male fetuses examined by doppler flow ultrasonography, the donut-like appearance is absent and doppler flow variation is largely restricted to the centrally located blood vessels. That appearance is shown here:

Image size: 820 x 614px  Author and copyright. Dr Stephanie Bucca: Doha, Qatar. stefbucca@gmail.co.

Some find doppler flow imaging less useful than others, deferring to the appearance of male and female gonads on B mode ultrasonography alone. This is because movement of the fetus itself can cause considerable echogenic noise during doppler flow ultrasonography.

The author wishes to acknowledge the assistance of  Drs Stephanie Bucca, Juan Samper and Carlos Pinto in creating this LORI entry.

Video (click on image and decrease page size to view at optimal resolution):

Video (PENDING) size 614 x 480px. Assembled and edited by Dr Rob Lofstedt (lofstedt@upei.ca). Copyright; Dr Carlos Pinto (tubercle files) Carlos.Pinto@cvm.osu.edu and Dr Juan Samper (gonad files) jsamper@telus.net. 

References:

1. Bucca S. 2005. Equine fetal gender determination from mid- to advanced-gestation by ultrasound. Theriogenology 64:568–571

2. Renaudin, C.D., Gillis C.L. and Tarantal, A.F.  1997 Transabdominal combined with transrectal ultrasonographic determination of equine fetal gender during Midgestation. AAEP proceedings. 43: 252-255.

3. Resende H.L. et al. 2013. Determination of equine fetal sex by Doppler ultrasonography of the gonads.Equine Vet J. 2013 Nov 15. doi: 10.1111/evj.12213. (Epub)

The reproductive tract of a 10 month equine fetus

Keywords: uterus, fetus, ovaries, equine, anatomy.

At about 90 days of gestation the fetal gonads of both sexes start to increase in size and reach maximum diameters at about 7 to 8 months of gestation. Interestingly, the growth is due to hyperplasia of interstitial tissue, not oocytes or seminiferous tubules. In fact, by 7 to 8 months the fetal ovaries are larger than the maternal ovaries. After this peak in gonadal growth, the fetal gonads decrease in size to about one tenth of fetal maximum.

Equine fetal ovaries in both sexes have long been known to be a substantial source of androgens. These androgens are aromatized to various estrogens. Increasing and decreasing estrogen production by the equine placenta during gestation (a feature often used in pregnancy diagnosis) parallels the growth and regression of the fetal gonads. However, it has only recently been shown that the gonads are also a substantial source of inhibin (not AMH) but the function of this inhibin production is not yet known.

In this ten month old equine fetus, the ovaries are still relatively massive.In the image below, the right kidney of the fetus lies between left and right ovaries. The uterine tube (fallopian tube) is shown here, crossing the ventral surface of the left ovary. The left and right horns and body of the uterus are also visible, a small fold in the caudal part of the uterine body, indicating the approximate location of the cervix.

Image size: 1500 x 1500px

The image below is a dorsal view of the excised tract seen above. The massive size of the ovaries compared to the rest of the reproductive tract is remarkable. The caudal part of the tract (from the cervix caudally) has been twisted anticlockwise to reveal the urethra (yellow arrow) and the clitoral sinus (green arrow). R= Rectum.  The small black arrow indicates the position of a partially perforate hymen!

The intercornual ligament (more of a feature of the bovine than the equine tract) is clearly visible here, as are the (middle) uterine arteries.

Image size: 1500 x 1130px

Selected reference:

Tanaka, Y et al. 20013. Localization and secretion of inhibins in the equine fetal ovaries. Biol.Reprod.328-335

Aging of the fetus using the fetal eye

Keywords: eye, fetus, equine, aging, ultrasound

The fetal eye is seen here as a large anechogenic circle in the skull of the foal. Its size has been used to determine the approximate age of the fetus.

Image size: 1052 x 687px

To estimate fetal age, the two largest diameters of the eye were measured and the sum of those results is plotted against a chart as shown. The chart was adapted from that originally published by McKinnon A.O. et al 1988. Note that the growth curve is curvilinear, not linear as has been suggested in earlier studies.

Newer data from Turner et al showed that the days before parturition (DBP) could be predicted with some assurance by measuring only the length of the fetal eye, centering the cursors over the lens to standardize measurements. Useful measurements could be obtained as early as 90 days of gestation. It was also emphasized that ponies had smaller eyes than those of horses at any given gestation and that allowance should be made for that fact when estimating fetal age.

Important: In cases of impending ventral rupture and neonatial isoerythrolysis etc, when foaling may need to be induced, these measurements are probably not accurate enough to decide on the correct time for induction. Milk electrolyte changes should be used instead.

In the author's experience (Lofstedt and Ireland 2000) in estimating the volume of sphere-like structures, it is more accurate to use the cubed value of the largest diameter of the structure than either the largest diameter, the sum of diameters, the circumference or the cross sectional area of the structure. Because volume is in effect, the actual size of a sphere-like structure, cubing a maximum diameter may be more useful than a simple diameter in future studies of this nature.

References:

Bucca S., Fogarty, U., Collins A. and Small V. 2005. Assessment of feto-placental well-being from the gestation to term: transrectal and transabdominal ultrasonographic features. Theriogenology. 64: 542-557

Turner, R. 2006. How to determine gestational age of an equine pregnancy in the field using transrectal ultrasonographic measurement of the fetal eye. Proc. AAEP 52: 250-255

Lofstedt R.M. and Ireland W.P. 2000 Measuring sphere-like structures using transtrectal ultrasonography. Vet Radiol Ultrasound.  41:178-180.

McKinnon A.O., Squires, E.L. and Pickett B.W. 1988. (No title) Eq. Reprod. Ultrason. Bulletin number four.  Fort Collins, Colorado State University animal reproduction laboratory. 31-40.

Severe skeletal malformation in a foal

Keywords: dystocia, equine, mare, radiograph, wryneck, fetus

A pluriparous Standardbred mare was presented for dystocia of several hours duration. The referring veterinarian reported the presence of "a severely deformed" foal that precluded normal delivery.

An epidural was given and the beta 2 agonist clenbuterol, was administered IV and the pregnancy was examined per vagina. 

A dead foal was in anterior longitudinally presentation and dorso left-ilial position. It had

Image size: 1500 x 997px

an obvious wry-neck. Wry-neck is permanent in-utero fixation of the neck in a flexed posture; unique to horses among domestic animals.  The head of the foal was also deformed. Initially, one gained the impression that there was bilateral shoulder flexion with both forelimbs retained. 

Using a fetotome, the head was removed uneventfully but when an attempt was made to locate the forelimbs, they appeared to be absent.  Because of the absence of the forelimbs, uterine tone and an inability to rotate the foal into a dorso-sacral position, the foal was delivered by cesarean section.  The mare's recovery was uneventful.

Radiology showed that both the left and right scapulae were present but only the right forelimb was present.

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Also, the right forelimb was vestigial, about the thickness of a thumb and it was also rotated on its longitudinal axis, so that the hoof faced backward. There was severe scoliosis and the head of the left femur did not articulate with the acetabulum.