On April 26, Ann Wachira was on her way to a burial in Kinunya village, Kirinyaga county. She never returned.
The next day her decapitated body was found in Athena area in Thika West subcounty.
Such killings prompt talk of ritual murder and witchcraft.
Three weeks ago, a head was found in Masinga Dam in Embu county.
On Tuesday, a postmortem at ThikaLevel 5 Hospital mortuary confirmed it was Wachira's head.
The mother of five was four months pregnant and has suffered injuries to her womb before she was beheaded.
When she did not return home in April, her husband he reported the matter to Kianyaga police station.T he couple had reunited in January.
Police in Thika are investigating how the body was found in Thika, yet she lived elsewhere.
Area DCIO Hussein Bakari said they were working closely with Embu and Kirinyaga counties to unearth motive for the murder and arrest the killers.
He called on anyone with information to report to the police.
