There is a condition, abbreviated CAH, that might lead to an intersex condition (genitals of both male and female). A steroid known as dex might reduce the impact of CAH (I won't make any claims to the accuracy of my summary, if you really want details, please follow the links). Thus the conjecture is that dex might heighten the feminine traits of a fetus and the girls thus born won't become lesbians. This particular line of research has all kinds of ethical issues, even if the lesbian component is ignored. I'll leave that for others to explore. I'll also set aside the irony of denying that homosexuality has a biological component while researching ways to biologically prevent it.
But this is a good opportunity to look whether preventing homosexuality is a good idea. Some of the reasons why a parent might want to make sure their child is straight.
* Spare a child the unhappiness of being persecuted for being gay.And behind all that is the desire that the little girl should grow up to be properly subjugated to a man so he can keep her barefoot and pregnant.
* Guarantee the highest probability of having grandchildren.
* Have a child more like themselves for a more complete connection with that child.
* Avoid sin.
Alice Dreger of Psychology Today provides the rebuttal:
* The drug dex is highly risky even for the things it has been approved to treat.
* Homosexuality should not be seen as a problem to be cured. The solution to persecution is to change society to make gays more accepted.
* Forcing people to conform to the most conservative social norms is anti-democracy.
* Children are inherently unpredictable. Someone who only wants a child who is a straight boy with blue eyes and a high IQ is not ready to be a parent. Being a parent isn't about living your life through your child's success.
* Puppies make wonderful grandchildren. There's also less trauma in leaving them in a kennel.