As part of the hagadah there is an extensive discussion where various verses are discussed in depth. One of the verses, Devarim 26:7, says that "God heard our pain" (וירא את ענינו), this is interpreted in the hagadah as refraining from martial relations. In the Venice 1629 edition of the hagadah this is illustrated by having husband and wife sleeping in separate beds.[As you can also see, for some reason the text of this edition has two yuds in the word ענינו I don't know why.]
Also, you can see in the top left hand corner of the illustration (click on the picture for a more detailed view) a lamp is lit as well. I assume this was also to show the lack of marital relations. The law on Yom Kippur is that one needs to have a light on, according to one understanding this is so one will not come to have relations with ones wife. Perhaps this was used here for the same effect. This understanding is bolstered by the fact the Talmud in Yoma learns the prohabition against marital relations on Yom Kippur from the Eygptian slavery. (Yoma, 74b)
According to one scholar, Israel Yuval, this understanding of the verse is polemical in nature. He explains that when the Jews were prohibited from martial relations this was "pain" as this "counteracts the claim of Jesus' miraculous birth." If one could have a child born through miraculous means, then it would mitigate the effect of abstinence. Consequently, we are emphasizing the Jewish view is that such abstinence is harmful.
[However, some have questioned Yuval's emphasis on finding Christological elements in the hagadah.]
Sources: Yerushalmi, Haggadah and History, plate 50; Joshua Kulp, The Origins of the Seder and Haggadah, Currents in Biblical Research, 4.1(2005) 109-134 (discussing Yuval and summarizing the state of the current literature); Safrai and Safrai, Haggadah of the Sages, 136-138.