Now, this is odd: they made a specific point of Nice DI Vanessa tenderly touching the 'couple' photo of her and Soldier Halfpenny pinned to the fridge...the only thing pinned to the fridge (unlike the jumble stuck all over most people's fridges).
The same fridge Andrew would've opened to spike the juice.
Admittedly, the woman in her photo could've just been her best friend, or sister. But surely there'd be other 'coupled' pics around the house, too, and he would've had ample time to rifle through her personal stuff.
Maybe he got the shock of his life by twigging she was in a same-sex relationship and pregnant before he raped her, abandoned his original plan to claim she had 'consensually' slept with him, and proved even worse bastardish and sick behaviour by deciding to cause loss of baby instead. Don't even want to think how.

Payback for her subjecting him to police investigation and making it clear she's onto him and believing Laura/ payback for rejecting his offer of a date/ payback for her daring to prefer women and not find him irresistible in the first place.
Theory full of holes and unlikely, I realise! Because, assuming he wore a condom, he'd still need to ensure nothing remained to indicate a SA had taken place...and he'd either have to prevent her from seeking medical help at all, or guarantee he was in charge of any treatment.