Obado, who initially denied having an affair with Otieno, was arrested after DNA testing confirmed he was the father of the seven-month-old foetus that died with her.
A post-mortem showed that Otieno had likely been raped, strangled and stabbed multiple times before dying.
“Sharon and her unborn baby lost their lives in a gruesome and horrifying manner in the hands of her killers,” Kenya’s chief prosecutor Noordin Haji said in a statement.
Haji alleged that Obado and Otieno had been in “an intimate relationship” and that when Otieno became pregnant Obado was “unhappy about it”.