To achieve a snug fit and lift the breasts, the fabric used for a push-up bra should be elastic and supportive, like nylon, spandex, or polyester. The cups or straps could be made out of lace or other ornamental textiles to give them a more feminine feel. 

Types of Fabric For Push-up Bra:

Depending on the manufacturer and design of the bra, several fabrics may be utilised for push-up bras. However, the following materials are frequently employed in push-up bras:

Nylon: Nylon is a strong, long-lasting, and lightweight synthetic material. It is frequently used in push-up bras because it is cosy, stretchy, and offers strong support.

Spandex: Stretchy apparel frequently uses this type of elastic fibre. To create a fabric that is elastic and supportive, it is frequently combined with other materials like nylon or polyester.

Polyester: Polyester is a supple, wrinkle-resistant, and lightweight synthetic fabric. It is frequently used in push-up bras since it is simple to maintain and offers strong support.

Background information : https://femposh.com/4-types-of-febric-for-push-up-bra