A Medical Description
Swyer syndrome - also called 46XY complete gonadal dysgenesis (lack of development of the gonads) - is a condition in which people with one X chromosome and one Y chromosome (i.e. male) have a female appearance.  People with Swyer syndrome are usually raised as females, have a female gender identity, and have typical and fully functional external female genitalia.  Internally, the vagina and fallopian tubes are usually normally formed, but the uterus is often small and underdeveloped.  The gonads (ovaries or testes) are not functional and therefore they are infertile. 

A 10-year old girl suffering from Swyer syndrone.  Click for full image.  Warning: potentially offensive picture.

Most individuals with Swyer syndrome do not experience any symptoms of this until their early teens when they fail to enter a female puberty and don't start having menstrual periods (menarche).  In a young teenage girl, her ovaries greatly increase their production of 'female' sex hormones such as estrogen at puberty (age 12-13), triggering dramatic physical changes such as breast development.  It is possible but unusual for this to happen in a girl with Swyer syndrome without hormone replacement therapy.  She lacks ovaries, and the tiny amounts of estrogen produced by other organs is usually sufficient estrogen to trigger puberty. The lack of estrogen also means that the development of male traits resulting from having XY genes is not hampered, most obviously a growth in height to 6 feet (182 cm) or more is commonplace.

Three teenage girls diagnosed as having Swyer Syndrone.  Note the widely varying degree of breast development - roughly Tanner II, III and IV/V.  No more than one in three is likely to have reasonable breast development naturally.  Estrogen hormone treatment is often essential to trigger breast development.

Swyer syndrome is most often diagnosed age 14-15 when a young woman seeks medical assistance due to her limited development of secondary female characteristics and lack of any menstrual bleeding (medically called primary amenorrhea).  Tests can then discover that she lacks ovaries and, therefore does not have sex hormones (estrogen or progesterone) that are required to undergo puberty. For example, Kiana from Belgium says:

Kiana, age 19.  10 cm taller and far happier with her body than three years earlier.

"I was a late bloomer. Not only was I the smallest in the class, I didn't develop any breasts and I didn't have my period. Still, I was confident that my puberty would get under way. I didn't question the fact that I wasn't already falling in love or dating boys like the other girls my age. But ... the older I got, the harder it became to stay optimistic. I compared myself to my older sister, who started puberty when she was twelve, and even my seven-year-younger sister seemed to catch up with me. In the fall of 2019 (age 16), after a series of tests, I was diagnosed with XY gonadal dysgenesis, also known as Swyer syndrome.  In January 2020, I began taking hormones [and] my body is gradually starting to look a bit more feminine ... I've recently started taking additional estrogen to artificially provoke periods. In itself, menstruation has no real function for me, but it feels nice to know that my uterus is cleaned monthly."

For various reasons (ironically including preventing unwanted pregnancy!) doctors often prescribe suffers with oestrogen in the form of the contraceptive pill.  Even this small amount is usually sufficient to apparently solve problems such as rare and irregular menstruation. 

A major differentiator between AIS and Swyers is generous vs limited breast development.  Breast augmentation is often sought, as shown here.

When hormone replacement therapy is started, these girls will develop enlarged breasts, underarm and pubic hair, regular menstrual cycles and other aspects of normal development during puberty.

It is then treated with hormonal replacement therapy including replacing estrogen and progesterone that is usually begun from puberty onward. In addition to helping with normal development of secondary sexual characteristics, hormone replacement therapy can also help prevent bone loss and thinning (osteoporosis) later during life.  The undeveloped 'streak' gonads are usually removed surgically because they place affected individuals at an increased risk of developing a gonadal tumour.


Sexual Intercourse
The vast majority of women suffering Swyer syndrome have a typically female appearing vulva, the only difference being the suggestion in some studies of a larger than average clitoris.  The vagina is also normal, unlike woman suffering from AIS it doesn't lack vaginal depth and penetrative sexual intercourse is very unlikely to reveal any problem for either participant.  

Women with Swyer can climax and achieve orgasm during sexual activity.  A 2006 psychosexual study which included three women with Swyer syndrome speculated that this might be less frequent than for cis-woman, but provided no evidence for this and only recommended further research.

A review of the admittedly few on-line sources suggests that women with Swyer syndrome do seem to experience increased sexual problems and impairment of sexual function compared to cis women.  Surgical procedures such as a widening of the vaginal entrance seem common in this small and self-selecting sample.

Pregnancy
Because women with Swyer syndrome lack ovaries, they are infertile.  However, through hormone management (see the summary to the right), the uterus can achieve almost normal dimensions and is able to sustain pregnancy.  The woman can then become pregnant and carry a baby to term through egg donation and subsequent assisted reproductive technology.

The anatomic properties of the uterus and surrounding structures may not permit normal dilatation and labour, so a C-section is the normal method of delivery.

Only a small proportion of women Swyer become pregnant as it's an expensive procedure requiring extensive medical supervision.  Also, the baby will not be genetically related to the mother, unless donated by a close relative such as a sister.

Case Studies

Hayley Haynes shown pregnant and with her twin babies - Avery and Darcey.

Hayley Haynes

Halyey was raised from birth as a girl, and only learnt age 19 that she suffered from Swyer syndrome and was genetically XY male. 

After marriage to her husband Sam, she desperately wanted to bear children and received treatment from the Royal Derby Hospital in the UK. 

On 24 December 2014, age 28, she gave birth to twins.  Press reports said that extensive hormonal development had stimulated the development of her embryonic uterus, and then in vitro fertilization technology (IVF) was used to make her pregnant - donated eggs were fertilized with her husband's sperm and successfully implanted into her uterus. 

Very confusingly the press reports said that Hayley had AIS, which is very implausible as there is no record of a suffer having even an "embryonic uterus".  It was perhaps an assumption made by one reporter after some research, which was then repeated by other outlets.  I actually contacted the hospital directly about this anomoly, but never received the promised response from a member of the medical team that treated Hayley.

Sara Maria Forsberg  

Sara is a successful singer, songwriter and media personality, who also has a strong on-line presence on social media platforms.

She was born in Finland in May 1994, although her native language is Finnish she is fluent in English, having lived in both the USA and UK as a child.  She began her music career in 2013 with videos posted on YouTube channel.  Her video What Languages Sound Like to Foreigners went viral and in 2014 she was signed by her first record label.  She has since  released numerous singles and several albums, with varying success.  She has also worked extensively in the media, e.g. appearing as a judge in the Finish TV verson of  Got Talent, and the hosting the British TV show Remotely Funny.  In October 2023, Sara revealed that she was born intersex and had been diagnosed with Swyer syndrome syndrome as a teenager.  

Ali von Klan

Ali has made a very positive biographic video on YouTtube describing how age 16 she discovered that she was intersex and how she has since coped with that. Ten years later she is clearly an activist for LGBTI community, but in a positive rather than confrontational way.

Jeanne Nollmann
An interesting documentary following the battle of "mother of two" Jeanne Nollman against a "mystery disease" which proves to be Swyer Syndrome can also be found on YouTube.     

But it does have some problems in that it never explains that her children are adopted and hides the fact that after initially being diagnosed with AIS age 19, Jeanne actually knew by age 25 that she suffered from Swyer Syndrome.