Baby X by Kira Peikoff

When any biological matter can be used to create life, stolen celebrity DNA sells to the highest bidder-or the craziest stalker-in this propulsive thriller.
With a vivid imagining of the future, Gattaca meets Black Mirror in Kira Peikoff's Baby X.
In the near-future United States, where advanced technology can create egg or sperm from any person's cells, celebrities face the alarming potential of meeting biological children they never conceived. Famous singer Trace Thorne is tired of being targeted by the Vault, a black market site devoted to stealing DNA. Sick of paying ransom money for his own cell matter, he hires bio-security guard Ember Ryan to ensure his biological safety.
Ember will do anything she can to protect her clients. She knows all the Vault's tricks-discarded tissues, used straws, lipstick tubes-and has prevented countless DNA thefts. Working for Thorne, her focus becomes split when she begins to fall for him, but she knows she hasn't let anything slip-love or not, his DNA is safe. But then she and Thorne are confronted by a pregnant woman, Quinn, who claims that Thorne is the father of her baby, and all bets are off.
Brilliantly plotted and terrifyingly prescient, Baby X is an unpredictable and relentless speculative thriller perfect for fans of Blake Crouch and John Marrs.