Listings name polyester, a 95% rayon / 5% spandex blend, and 100% polyester as the primary materials.
Fit features that add room include empire/high waistlines, gathered/empire waists, adjustable tie-front details, and shirred backs for extra stretch.
Descriptions commonly recommend them for baby showers, maternity photoshoots, casual outings and everyday wear (including summer outings, brunch, or beach days).
Comfort comes from soft, stretchy fabrics (including a 95% rayon/5% spandex blend and at least one listing noting 4-way stretch), shirred backs for added give, and lightweight, flowy waist designs for ease of movement.
Care guidance varies by listing but most note machine washing. Drying instructions differ (tumble dry, hang to dry, or line/lay flat); one listing specifies a gentle cycle and advises avoiding high-heat ironing.
Several listings describe the fabric as lightweight, and at least one specifically calls out lightweight, breathable 100% polyester.