When was "ladyparts" first used to describe the genitalia of a woman?

It appears to be very recent slang, and hasn't yet been added to any dictionaries other than Urban Dictionary (defined in 2009 and quoted in another definition in 2006) and Wiktionary (added in 2011), as defined:

ladyparts (plural only)
(informal) The breasts and/or genitalia of a woman or women.

The earliest use found in Google Books is in a snippet from 1970, The Pretenders: A Novel by Gwen Davis, but this may be a one off rather than an indication it was well-known slang. It's also a snippet so there's a chance the 1970 date is incorrect:

Lady parts, lady's parts and ladyparts were used in Usenet posts in the '90s, for example this from 1999:

What's a 'front passage'?

A vagina, Kerry, a vagina.

Ahhhhhh

You mean the ladyparts

It was either already popular or was popularised by American sitcom The 70's Show, where it was used at least twice in 2002.

That '70s Show - "Heartbreaker" (29 Oct. 2002, season 5, episode 4):

The doctor told me I started menopause.
...
I know you wanted a baby, but I'm not really sure what to say...
mainly because I'm not really sure what menopause is.
Are you-Are you gonna, like, lose your hair?
Shut up!
She's not losing anything.
This just means that from time to time-
A woman's body- ( Clears Throat )
Kitty, explain it to the boy.
I'm just getting some juice.
Hey, Mom, maybe you should talk to Grandma about this.
Now, that's an idea.
I mean, we're just ignoramuses.
Okay, okay. Scoot.
Is it- Is it like a lady-parts thing?

That '70s Show - "Over the Hills and Far Away" (19 Nov. 2002, season 5, episode 6):

00:03:42 we need to have a talk about that horrible thing that's taken over your mother.
00:03:47 You mean, her ''change of life''?
00:03:51 Thought we were calling it ''the lady-parts problem.''
00:03:56 It goes by many names.
00:03:59 Now, we're dealing with a tricky enemy here.