Despite their apparently rigid construction, 18th century bodices were actually fairly malleable when it came to accommodating pregnancy. The use of stomachers left the front of the bodice open allowing pregnant women to either use larger stomachers or forgo them entirely and fasten to bodice with ties. You can see with this quilted robe à la française from circa 1750, how widely the bodice could be expanded with the use of ties.
Fashion 18th Century ball gown dress ensemble costume circa from 1752-1775. Made from very fine silk, lace and trim with embroidered small flower floral pattern in off white woven into the pale blue background. Hat decorated with millinery flower.