How do I make a sprite expand from its center using pygame.transform.scale?

Question

I am making a game where I am trying to have an enemy grow in the air then drop like a bomb. For the most part, everything works well. The only problem I have is that it is while it is growing, it is moving down and right.

Here is the code I am using

import pygame

            
class BloodyTear(pygame.sprite.Sprite):
    def __init__(self):
        super().__init__()
        self.sprite=pygame.image.load('image')
        self.image = self.sprite
        self.rect = self.image.get_rect()
        self.rect.x =500
        self.rect.y = 50
        self.size1 = 10
        self.size2 = 10
        self.mask = pygame.mask.from_surface(self.image)
        self.size = self.size1, self.size2      
        
    def update(self):
        
        if self.size1 < 135:
            self.size1 += 1
            self.size2 += 1
            self.size = self.size1, self.size2
        self.image = pygame.transform.scale(self.sprite, self.size)
        if self.size1 == 135:
            self.rect.y += 3
            self.mask = pygame.mask.from_surface(self.image)
        if self.rect.y >= 500:
            self.kill()
        
    def collide(self, spriteGroup):
        if pygame.sprite.spritecollide(self, spriteGroup, True, pygame.sprite.collide_mask):
            pass




pygame.init()
blood = BloodyTear()
window = pygame.display.set_mode((800, 800))
clock = pygame.time.Clock()




bloddsprite = pygame.sprite.Group()



bloddsprite.add(blood)
run = True
while run:
    clock.tick(60)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

   
    bloddsprite.update()
    
    window.fill(0)
    
    bloddsprite.draw(window)
  
    pygame.display.flip()

pygame.quit()
exit()


           

        

I tried using get_bounding_rect() but it didn't seem to change anything. I'm not sure exactly how to fix this.