Brittany Mahomes made a quick outfit change before husband Patrick Mahomes’ lavish birthday bash.

The soon-to-be mother of three swapped her vintage Chanel mini dress for a halter neck Givenchy number on Sunday night following the Kansas City Chiefs’ nail-biting win against the Cincinnati Bengals.

Brittany put her growing baby bump on display in the navy-and-white striped dress ($1,300), which she paired with minimal jewelry.

Although the blond beauty kept her hair in the same Pamela Anderson-inspired updo, she traded her Chanel-branded loafers for a pair of platform Prada sneakers ($1,120) and took off her Chanel pearl necklace.

Brittany and Patrick Mahomes
Brittany Mahomes changed into a striped Givenchy dress for husband Patrick Mahomes’ birthday party on Sunday.randimahomes/Instagram

Brittany Mahomes at the chiefs game.
She wore a chic Chanel look earlier in the day.brittanylynne/Instagram
Brittany’s mother-in-law, Randi Mahomes, shared a family photo from her son’s 29th birthday, giving fans a better glimpse at her lowkey look.

Most of the Mahomeses dressed casually for the event in white T-shirts, however, the birthday boy stepped things up with a Louis Vuitton monogrammed tee.

The NFL star paired the patterned top with tan checkered trousers and matching sneakers. He wore the same ‘fit before the big game earlier in the day.

Following the 26-25 victory, Patrick invited his close friends, family and teammates over to his palatial estate — which features a basketball court, 50-yard football field, putting green and more.

Givenchy dress.
The halter neck dress retails for $1,300.

Prada sneakers.
The WAG also swapped her Chanel loafers for a pair of pricey Prada Sneakers.
Prior to the party, Brittany gave fans a behind-the-scenes look at some of the over-the-top decor.

Guests were immediately greeted by a large black-and-red balloon arch with a sign that read, “Patrick’s 29th.” The couple also included the quarterback’s logo into the decor.

The front door was decked out with silver balloons covered with red LED lights and a mirrored “29.”

Partygoers drank from personalized cups with Patrick’s face on it and enjoyed his massive cookie cake in lieu of a birthday cake.

Brittany Mahomes and her kids
Mahomes wore her hair in the same ’90s-style updo all day.brittanylynne/Instagram

Patrick and Brittany Mahomes kissing.
The Mahomeses hosted their friends and family after their win against the Cincinnati Bengals.brittanylynne/Instagram
Throwback photos of the football star were blown up and placed throughout the mansion.

The couple also rented a photo booth for the party, which was seemingly a hit amongst guests — including Taylor Swift.

The pop star, 34, joined Sheawna Weathersby, the wife of Chiefs defensive tackle Chris Jones, and Chariah Gordon, the fiancée of Chiefs wide receiver Mecole Hardman, for a few silly pictures during the soirée.

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Patrick Mahomes' birthday party.
The couple went all out for the birthday bash.brittanylynne/Instagram

Patrick Mahomes cups
The party was complete with personalized drinkware.brittanylynne/Instagram
In the snaps shared on Weathersby’s Instagram Stories, the “Fortnight” singer posed with red cat-eye sunglasses while snuggled up to the other WAGs.

Although Brittany changed for the party, Swift seemingly stayed in the vintage Chiefs T-shirt dress that she wore to Arrowhead Stadium earlier today.

The hitmaker paired the red top with thigh-high black boots, a black Louis Vuitton purse and surprisingly affordable jewelry.