While seen as a bit "playing god" to some or "coming with grave side-effects" to others some highly developed nations have medicines and treatments to delay or even stop biological clock phenomena, and as such they have fewer kids and their populations stagnate and decline. Thus one scientist whose research is a little "under the table" was given a decent amount of grant money in order to boost the declining and aging population.
Stewart in his lab wondered how he became essentially some mad scientist quack on the government's payroll... Oh right he majored in human biology, and wrote a student paper or two on the potential triggers of the biological clock phenomena... Then when he graduated he was offered a position and now here he was working on a few mad scientist experiments that surprisingly had a decent chance of working. The first thing he made was essentially just a female version of Viagra It just boosted a woman's sex drive tremendously. Stewart had the theory originally that a woman's biological clock phenomena started with the libido which then triggered the rest of the changes... Turns out the sex drive increasing with the woman's assets was merely corollary, and yet it was still a success in a sense and was sold discretely in pharmacies or in sex stores for some women who just wanted to be able to turn on their own sex drives... Which probably helped the birth rate so the government wasn't that upset at a "failed experiment"
Stewart had pondered what could potentially trigger the "biological clock" and even wondered if it were possible to turn it on for men... also just in case he needed to he'd toy with something to turn off the phenomena. He was still messing with the exact details but he had a few ideas.
The first was a sonic emitter, a special speaker, that would emit a tone which may make the body trigger the "biological clock" phenomena. The only issue in application is you can't target any one person in particular... also the particular sound it had to emit was currently unknown. The second was essentially just a flashlight that would shine a light of a certain frequency that may cause certain changes in the eyes or skin to trigger the phenomena. The Third were subliminal messages he could put inbetween frames of high frame rate videos which may cause a subconscious trigger. Finally a mixture of hormones that could be administered via a perfume for nasal and topical application, as an ingredient if administered orally, or rectally... theoretically he could just make it into a butt medicine as he had theorized that the butt and it's glands may contain most of the triggers for the phenomena... still he'd rather test the other ways first. All those experiments were mostly conjecture though as he still didn't know WHAT exactly triggered the phenomena... But the government was starting to want more and more answers so he'd have to get to field testing soon...