Maternity dress, possibly Natural Form era, via Time Travelers Antiques.
Historical style: Maternity fashion across the ages
19th century maternity style - nightgown.jpg ~ wow, I'd get pregnant just so I could wear it ;D
Green silk maternity dress with leg o' mutton sleeves, 1895-1900, via Mode Museum.
Late 1840s, America - Maternity dress of printed cotton
This maternity dress has been made with slits at the side, forming a drop apron at the front to allow for an expanding waistline. The front-opening bodice is unusual for this period, and allows ease of movement for nursing. This dress features a cross-over, front-opening bodice, which was unusual for this period. However this high-waisted style would have been most comfortable for maternity wear, allowing ease of movement for nursing.
Day dress of Empress Alexandra Feodorovna, 1900 From the State Hermitage Museum
Now that's a maternity dress.
Afternoon maternity dress by Emile Pingat, 1880s. The bodice had been altered significantly to accommodate a larger bust, but there had been no alteration to the piping around the bottom of the bodice, suggesting that the alterations were done by the maker. There are no alterations to the skirt. Given the manner in which the dress wanted to drape, we're wondering if this was a very fancy maternity dress made for a particular event.