Page 167 of this reference (Hayward, Maria, Dress at the Court of King Henry VIII. Routledge, Taylor & Francis Group, London and New York. 2007) advises that this is an early portrayal of maternity dress, “In her portrait drawing done by Holbein in 1528 and the celebrated More family group, the front of Cecily’s gown is laced in such a way as to accomodate her pregnant body (a reference to a black-and-white version of this portrait follows).” In the More family group, the gold portions of Cecily’s dress are gold brocade or cloth of gold and all of both sleeves can be seen. The original of the group portrait was done around 1527 so this image is assigned the date ca. 1527.
Her terse article in thepeerage shows she suffered the same fate as Sir Thomas More, her father, by being executed for treason in 1544. She married in 1540.
From Peter's photostream on flickr. Also posted to the Early 1500s - 1470 to 1550 Album here.
The vest over-bodice could be opened to allow expansion of the bodice (shown in gold) as pregnancy proceded. Her hood has the angular notch of an English gable hood, but the top curves round like a French hood.
Keywords: 1527, Holbein - Hans the Younger, Cecily Heron, Cecily More, More family, Heron family, English, straight coiffure, French hood, veil, strap, necklace, pendant, partlet, square neckline, chemise, bodice, laced vest over-bodice, bows, full tapered over-sleeves, maternity dress