One such factor may be hormones, the radical hormonal changes in the body of a transwoman, to approximately female norms after orchidectomy or SRS, might give a push towards a heterosexual orientation.

Observers often consider that on average transsexual women are more "female than [genetic] females" in their life style and social beliefs, and a few (usually those that transition in middle age) do seem to be almost a living stereotype of the feminine ideal.  Some transwomen undoubtedly strongly feel that as a woman they should only want to have sexual relations with a man, and in this instance any residual sexual attraction to women rather than men becomes both unimportant and something to be suppressed.  Going further, for a few transsexual women (like for some genetic women), marriage and even motherhood via the adoption of children becomes their overriding goal, and perhaps an ultimate symbol and proof of their womanhood.  Indeed, the Stepford Wives may be still be alive and well - albeit transsexuals!

While most heterosexual transwomen are heterosexual for reasons of choice and preference, it seems likely that in some instances the adoption of a heterosexual orientation is closely related to the transsexual woman's success in passing and assimilating herself as a woman.  Based upon the limited available evidence it can be suspected:

A) The younger a woman's age at SRS, the more likely a heterosexual female orientation will be, the obvious corollary being that the greater the woman's age at SRS, the more likely a lesbian or bisexual orientation is. 

B) The more "passable" a woman is (which is partly linked to her age at the time of SRS), the more likely a heterosexual orientation is.  It seems that for a variety of reasons about half of the women who were once heterosexual man (i.e. were exclusively sexually attracted to women) before their SRS, are heterosexual women afterwards (i.e. are exclusively attracted to men).

Social conformance even in the twenty-first century encourages the successfully passing transwoman to enter in to "normal" sexual relationships with men as far as she is physically capable, while intimate relationships with other women would risk "rocking the boat" and perhaps getting people asking some undesired curious questions.  

Entering into a committed relationship with a man undoubtedly tends to pull a transwoman away from any open acknowledgement of her transsexuality and male past, and encourages an apparently heterosexual orientation in public - what ever her secret inclinations might still be.  As the table above shows, many heterosexual transsexual women hide their male past from partners and even their husband, feeling (unfortunately often correctly) that the relationship may not survive this becoming known to him.  Even if the partner knows about and accepts the woman's transsexuality, their friends and his family might not be so open minded, and external pressures and prejudice could eventually destroy the relationship. 

Lesbian or Non-Sexual Transwomen
When a post-SRS transwoman enters in to lesbian relationships, or becomes non-sexual - avoiding any intimate relationships - the reasons tends to fall in to one of a few main categories:

1. Continuation of a relationship with a former wife or female partner on a sexual or non-sexual basis;

2. Continuation of a sexual attraction to women, if strong this may lead to a drift in to lesbian relationships, if weak it may lead to an avoidance of any sexual activity at all;

3. Sexual relationships with other transsexual women.  [see below]

Non-sexuality can also be caused by:

1. A genuine lack of sexual urges;

   Kimberley Langley legally married her lesbian partner after having a sex reassignment surgery.

2. Poor surgical results - for example lack of vaginal depth, poor appearance of the vulva, or intercourse is painful;

3. Failure to attract desirable partners, for example due to an inability to pass convincingly;

4. A conscious suppression of inconvenient or undesired sexual urges, e.g. due to having AIDS or fear of possible discovery during intercourse;

5. Participation in a relationship in which the other partner doesn't want to engage in sexual relations.

Bisexual Transwomen
A relatively high percentage of transwomen enter sexual relationships with both men and women.  The reasons are varied, for example: one night stands; curiosity; and social conformance (e.g. a public relationship with a man but secret lesbian relationships).

Transcouples
It is not unusual for a transsexual woman to enter in to a relationship with a another transsexual, usually another male-to-female MTF) woman but occasionally a female-to-male (FTM) man.  An important, though perhaps not overriding, benefit of such a relationship is the couples shared experiences, support and understanding about each others transsexuality, something which a relationship with a non-transsexual person can not provide.  Also, the transcouple do not need to face the risks and worries of going stealth in order to establish and maintain the relationship with their partner.

A significant proportion of transsexual women admit to being attracted to other transsexual women, indeed one small survey found that half of the respondents were strongly attracted to other transsexual women.  Naturally this attraction often leads to relationships, both of a "one night stand" and of a more permanent nature.  Sexually, these are technically lesbian relationships, but interestingly the partners are frequently not attracted to non-transsexual genetic women.

When a MTF woman enters in to a relationship with a FTM man, generally both partners are insistent that it is a conventional, heterosexual relationship.

Young Transsexuals
Unlike older transsexuals, the sexual orientation of young transsexual women (meaning those who transition and start treatment before age 20) is rarely in doubt, they are usually as fervently interested in boys as any teenage girl! 

Tamalah, who transitioned at age 18, says "I knew from as early as I can remember that I was a girl.  I didn't consider myself gay, I considered myself a heterosexual female."  Both before and after the surgery, she presented herself as a woman and was often asked out by men. "I figured what they didn't know wouldn't hurt them, as long as I didn't sleep with them."

To please her boyfriend, Maxine had breast implants at age 17.  He moved on, but she had her SRS three years later.

Maxine notes "At age 14 I experienced my 'first time' while on holiday ... [he was] six foot tall, wash board belly, unbelievably sexy.  He chatted me up on the beach and we went to his hotel room.  He slowly undressed me.  It was beautiful.  There was nothing I wanted more that night than to be a whole woman."

A few years later Maxine had a relationship with a strongly heterosexual man: "Omar was a beautiful man but everything had to remain secret.  The first time was very sensitive - however he missed me not having a bosom.  He got a terrible complex, ... deep down he believed that I was really another man.  I wanted to be the perfect partner for Omar, and dreamt of us having a family.  I longed to be a woman, and as I fell in love with him I resolved that it was Maxine or nothing."

Getting Physical
Almost inevitably there is some degree of correlation between sexual satisfaction and successful physical feminisation, including high quality surgery.  Good physical feminisation results in more relationships with attractive and 'sexy' partners, and hopefully more enjoyable physical sensations during everything from petting and nipple sucking, to clitoris stimulation and vaginal penetration.  However, it is very difficult to divide physical feminisation decisions made primarily on sexuality grounds from those made on other very important grounds such as increased pass'ability and self image. 

Individual priorities vary dramatically, as the requests made of surgeons in relation to constructing or enhancing the female secondary sexual characteristics of transsexual women show.  Good breasts (the definition of which vary from girl to girl) are a clear top priority, while the development and subsequent maintenance of a vagina suited to accommodating a penis can be a surprisingly low priority - for older women in particular there seems to be a divergence between intensions at SRS and the reality a few years afterwards.  A reasonable speculation is that some transwomen would prefer having a natural looking vulva area or a sensitive clitoris over good vaginal depth, for sexual reasons that include lesbianism and masturbation desires.