BGDB Sexual Differentiation - Abnormalities

Reproductive Abnormalities

This page introduces the statistical data associated with birth abnormalities in the genital system in Australia and also briefly introduces some of these defects. For more detailed coverage look at the Genital Abnormalities Notes. Abnormalites associated with development of secondary sex characteristics including mammary development are not covered in this current practical class.

Note that some abnormalites affect physiological function, while others through mainly perturbed endocrine effects, can impact upon not only other systems but also have neurological ramifications upon sexual identity. Then finally look at the online information provided to the general public on birth defects associated with genital system development and sexuality.

Genital abnormalities fall into several categories: chromosomal, intersex, gonadal dysfunction, tract abnormalities, external genitalia and gonadal descent.

Links: Genital System - Abnormalities

Gonadal Descent

Cryptorchidism an abnormality of either unilateral or bilateral testicular descent occurring in up to 30% premature and 3-4% term males Descent may complete postnatally in the first year, failure to descend can result in sterility.

Hernia Indirect inguinal hernia is a common condition in male infants resulting from a patent processus vaginalis allowing communication between the peritoneal cavity and the scrotal sac through which portions or loops of small intestine may herniate. This is a common surgical repair operation in young children. Hydrocele a fluid-filled cavity of eiter testis or spermatic cord, where peritoneal fluid passes into a patent processus vaginalis. Hydrocele of the testis is when a very small patent processus vaginalis may not herniate, but allow fluid to pass from the periotoneal cavity leading to the collection of serous fluid between the layers of the membrane (tunica vaginalis). Normal - fluid around the testicle is absorbed Noncommunicating hydrocele - fluid remains around the testicle Communicating hydrocele - fluid flows back and forth between the scrotum and the abdomen Hydrocele of the cord - fluid is located between the scrotum and the abdomen

External Genitalia

Hypospadia most common penis abnormality (1 in 300) from a failure of male urogenital folds to fuse in various regions and resulting in a proximally displaced urethral meatus. The cause is unknown, but suggested to involve many factors either indivdually or in combination including: familial inheritance, low birth weight, assisted reproductive technology, advanced maternal age, paternal subfertility and endocrine-disrupting chemicals. Infants with hypospadias should not undergo circumcision.

Opening of the urethra (meatus) on the inferior surface (ring) not at the tip. Other regions where urethra may open to the surface (dashed line).

Hypospadias is classified by the location of the opening

Glandular hypospadias is when external urethral opening is on ventral surface of glans penis. Penile hypospadias is when external urethral opening is on ventral surface of body of the penis. Penoscrotal hypospadias is when external urethral opening is at the junction of penis and scrotum. Perineal hypospadias is when external urethral opening is located on the unfused halves of the scrotum. Epispadias - Uncommon abnormality associated with the penis, 1 in 30,000 infant males, external urethral opening on the dorsal surface of penis.

Links: Genital System - Abnormalities

Internal Genitalia

Male

Ductus Deferens

Unilateral or bilateral absence congenital unilateral absence of the vas deferens (CUAVD), Congenital bilateral absence of the vas deferens (CBAVD) failure of mesonephric duct to differentiate frequent cause of obstructive azoospermia 75% of men with bilateral absence have at least one detectable common mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene

Female

A range of uterine and vaginal anatomical anomalies based upon the abnormal development and fusion of the paramesonephric ducts and vaginal plate development.

Uterine Duplication (uterus didelphys, double uterus, uterus didelphis) A rare uterine developmental abnormality where the paramesonephric ducts (Mullerian ducts) completely fail to fuse generating two separate uterus parts each connected to the cervix and having an ovary each. Failure of fusion of lower paramesonephric ducts, with either double or single vagina.

Septate Uterus

Unicornate Uterus - failure of the paramesonephric ducts to fuse. A single paramesomnephric duct has fused with the vaginal plate and now opens into the vagina, while the other forms a diverticulum.

Cervical: cervical agenesis, cervical duplication

Vagina Absence - Failure of sinovaginal bulb development to form plate, 1 in 4,000 to 5,000 female births.

Mayer-Rokitansky syndrome (MRK anomaly, Rokitansky-Küster-Hauser syndrome, RKH syndrome, RKH) congenital absence of the vagina, dyspareunia, vaginal agenesis.

Environmental Abnormalities

DES Diethylstilbestrol or diethylstilbetrol, is a drug that was prescribed to women from 1938-1971 to prevent miscarriage in high-risk pregnancies. The drug acted as a potent estrogen (mimics natural hormone) and therefore could also act as a potential endocrine disruptor. This led to a number of developing fetal reproductive tract and other abnormalities. In the female fetus, it increased risk of abnormal reproductive tract and also carcinogenic (cancer forming). In the male fetus, it increased the occurance of abnormal genitalia. The drug was banned by FDA (USA) in 1979 as a teratogen, it had previously also been used as livestock growth promoter and could have potentially entered the human food chain. (More? Endocrine Abnormalities | Abnormal Development - Drugs)

Additional Information

Cryptorchidism in common eutherian mammals.- Species comparison of descent timeline

References

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BGDB: Lecture - Gastrointestinal System | Practical - Gastrointestinal System | Lecture - Face and Ear | Practical - Face and Ear | Lecture - Endocrine | Lecture - Sexual Differentiation | Practical - Sexual Differentiation | Tutorial

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Cite this page: Hill, M.A. (2026, November 4) Embryology BGDB Sexual Differentiation - Abnormalities. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Sexual_Differentiation_-_Abnormalities

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© Dr Mark Hill 2026, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G