AITA for laughing at my gf’s pregnancy news?

A lesbian woman’s three-year relationship fell apart when her bisexual girlfriend announced she was pregnant after a long-term relationship. The couple had agreed to a threesome six months earlier to test whether she was attracted to men, and the original poster even picked her partner on Tinder.

What made the story more complicated was that the girlfriend continued the relationship in secret, citing work stress and “viruses”. The betrayal was only discovered when she couldn’t hide her morning sickness. Instead of repenting, the girlfriend asked for joint custody, which made the original poster laugh hysterically before packing up and leaving. The girlfriend’s friends and mother now call the laughter cruel, but the core issue remains infidelity and broken trust.

‘AITA for laughing at my gf’s pregnancy news?’

The relationship seemed solid until the girlfriend proposed a threesome to explore her bisexuality.

Mood shifts and morning sickness raised red flags the OP initially dismissed.

Confrontation revealed months of cheating and an unthinkable co-parenting demand.

Cheating disguised as “sexual exploration” is still cheating, period. The girlfriend took a single, mutually consenting “threesome” and turned it into a six-month secret affair, complete with lies about work stress and fake coronavirus to cover up the morning. Her audacity culminated in her asking her ex-boyfriend to take on the role of parent to a child conceived entirely outside the relationship. This is not unusual; it is betrayal masked in the language of identity.

Some might find the laughter cruel, a public humiliation in a moment of danger. However, involuntary laughter is a recognized stress response to overwhelming shock—psychologists call it “inappropriate emotion.” The ex-boyfriend was not mocking the pregnancy; she was cut off by the absurdity of being asked to co-parent her surrogate child. What made the story more complicated was that the girlfriend’s family demonized her ex-boyfriend to avoid responsibility for their daughter’s actions.

More broadly, socially: this case feeds harmful stereotypes that bisexuals cannot be monogamous. Relationship therapist Tammy Nelson explains: “Bisexuality describes who you are attracted to, not how many partners you need at once. Monogamy is a separate agreement” (source: Tammy Nelson, The New Monogamy: Redefining Your Relationship After Infidelity, 2019). The author respected all boundaries until those boundaries were erased without consent. Expecting a partner to accept infidelity, pregnancy, and parenthood under the guise of “exploring bisexuality” is emotional blackmail, not liberation.

See what others had to share with OP:

Social network users unanimously declared the OP blameless, condemning the cheating and co-parenting demand.

A couple of voices pushed back against stereotypes while reinforcing the OP’s right to walk away.

Light-hearted comments used irony to highlight the girlfriend’s audacity.

The OP entered a consensual threesome, not an open relationship, and discovered her partner had been conducting a secret affair for half a year. Laughter emerged from disbelief, not mockery, and the demand to co-parent a child conceived through deception is indefensible. Trust, once shattered by lies and a hidden pregnancy, rarely rebuilds.

Have you ever laughed in shock during a betrayal—did it help or hurt? When one partner changes the rules mid-relationship, where should the line be drawn?