Simplicity 4506 vintage sewing pattern, dated ca. 1962:

Maternity One-Piece Dress, Top and Shorts:

Dress and top have bateau neckline and back 6" zipper closing. V. 1 has front drawstring. V. 1 and 3 have set-in sleeves with self ruffle at lower edge. V. 2 and 4 are sleeveless and have self ruffle at lower edge. Shorts have side zipper and front drawstring. Front inset may be self fabric or purchased stretch panel.

Size 14:

Bust 34 inches /  87 cm

Waist 26 inches / 67 cm

Hip 36 inches / 92 cm

Pattern is unprinted, checked complete. Pieces A and C have some pieces of old tape, potting, small holes. Other pieces have spotting. Envelope is yellowed, has spotting and shelf wear.

More vintage maternity patterns here:

https://allthepreciousthings.com.au/collections/maternity