And they say women lose 90% of their eggs by age 30 ... Jennifer Aniston's newly refurbished, $21 million Bel Air mansion is a grazing site for chickens.

44-year-old Aniston and her fiance Justin Theroux just completed renovations on the sprawling 3.5-acre property -- which the couple purchased last year -- and Aniston decided to maintain the chicken coop.

FYI, Bel Air is one of the most exclusive neighborhoods on the planet ... and here's a fun fact -- the house featured on "The Beverly Hillbillies" is also in Bel Air.

Who's no spring chicken now?

But soft! What light through yonder window breaks? It's Jennifer Aniston, who continued her ridiculously hot Mexico vacation yesterday ... looking pensive in a sexy bikini and an exotic red sarong (the thing wrapped around her waist).

As we reported, Jennifer and her tatted-up fiance Justin Theroux have been kicking it in Cabo San Lucas over Christmas, and things just keep heating up.

Still unclear if Jennifer's pregnant -- but if you're wondering what it's like to get held up in Mexico ... just ask her boobs.

Who knew?  Justin Theroux is tatted neck to toe.

The pics were snapped in Cabo San Lucas, Mexico over the weekend.  Jennifer Aniston, who at 43 still looks mighty fine, and Justin were catching some rays when he stood up and revealed a back tat that looks kinda ... Asian-y.

Jennifer makes a yearly pilgrimage to Cabo around XMAS time and usually George Clooney follows suit -- this time with lucky Stacy Keibler.  And Rande Gerber and Cindy Crawford always make the trek as well.

FYI --There are reports circulating that Jennifer is pregnant.  If she's really pregnant, Jessica Simpson has been doing it seriously wrong.

Here it is ... undeniable proof that Jennifer Aniston is finally PREGNANT ... or not pregnant ... depending on if you can see a baby bump in this photo!!!

The former "Friends" actress was all smiles on her way into a spa in Beverly Hills this weekend ... with what appears to be signs of a "stomach" showing underneath her shirt.

Question is ... is her belly full of fetus??? Or perhaps she had a big lunch?? Or is she still really super-skinny and it's all just an optical illusion created by a couple of ill-placed wrinkles in her shirt?

Only Jen knows for sure ... but we should totally guess anyway -- so, we gotta ask ... 

We hate to speculate, but ...

Out on a shopping date in Beverly Hills with fiance Justin Theroux yesterday, the ageless Jennifer Aniston seemingly covered her midsection with both a shopping bag AND a jacket as she made her through a parking garage.

So we ask ...

Jennifer Aniston and boyfriend Justin Theroux are planning a wedding thousands of miles away from Hollywood ... TMZ has learned.

Sources connected with the Elounda Beach Hotel in Crete (where Aniston's dad was born, located about 230 miles south of Greece) tell TMZ ... Aniston was there recently, scoping the place out. Our sources say Aniston mentioned a July wedding.

The hotel website boasts a wedding package that includes:

-- A dedicated consultant
-- Legal, License Paperwork Requirements
-- Civil or Religious Ceremony outside of the Hotel’s Church 
-- Bridal Bouquet, Groom's Boutonniere, decoration of the club car
-- Bottle of champagne & Greek Wedding Sweets after the ceremony for the bride & groom

You get all that, plus a series of other complimentary services, for about $2,300. 

Aniston made that for roughly 2 seconds of work on "Friends." 

BTW, one of the hotel big wigs says Aniston hasn't settled on his hotel for the nuptials ... as he put it, "She has connections on the other side of the island as well."

Dressed similarly in hats, shades, black jackets, exposed belts and jeans, Justin Theroux and Jennifer Aniston roamed through NYC in the rain on Tuesday.

They are match made in hipster wardrobe heaven -- a habit Jen obviously inherited from Brad Pitt.

The same day Brad Pitt backtracked on his marriage comments by saying he was the dull one and not his ex-wife ... Jennifer Aniston showed a united front with her boyfriend Justin Theroux by walking hand-in-hand together in NYC on Friday.

Jen is definitely holding on to this man.