Madonna del Parto

A Madonna del Parto ("Madonna of Parturition") is an iconic depiction of the Virgin Mary shown as pregnant, which was developed in Italy, mainly in Tuscany in the 14th century. Examples include works by Taddeo Gaddi, Bernardo Daddi and Nardo di Cione, but the fresco by Piero della Francesca is considered the most famous one. The Madonna was portrayed standing, alone, often with a closed book on her belly, an allusion to the Incarnate Word. The works were associated with the devotions of pregnant women, praying for a safe delivery. Sometimes, as with a statue by Sansovino in the Basilica of Sant'Agostino in Rome, the depiction is of a Virgin and Child, but known as a Madonna del Parto because it was especially associated with devotions over pregnancy. Here the Virgin wears the Girdle of Thomas, a belt of knotted cloth cord that was a relic held in Prato Cathedral, which many depictions wear. 
Piero della Francesca.
The most famous work showing this subject is a fresco painting by the Italian Renaissance master Piero della Francesca, finished around 1460. It is housed in the Museo della Madonna del Parto of Monterchi, Tuscany, Italy.
Piero della Francesca finished it in seven days, using first-rate colors, including a large extent of "blu oltremare" obtained by lapis lazuli imported from Afghanistan by the Republic of Venice.
The fresco was at one time located in Santa Maria di Momentana (formerly "Santa Maria in Silvis"), an old country church in the hilltown of Monterchi. The edifice was destroyed in 1785 by an earthquake and the work was detached and placed over the high altar of the new cemetery chapel; in 1992 it was moved to the Museo della Madonna del Parto in Monterchi. The work was attributed to Piero della Francesca only in 1889. Its dating has been the subject of debate, ranging from 1450 to 1475. The 16th century artist and writer Giorgio Vasari wrote that it was completed in 1459, when Piero della Francesca was in Sansepolcro for his mother's death.
The fresco also plays an important role in Richard Hayer's novel "Visus", in Andrei Tarkovsky's film "Nostalghia", and in the poem "San Sepolcro" by Jorie Graham.
Piero della Francesca's Madonna has neither books nor royal attributes as in most predecessors of the image, nor does she wear the girdle. She is portrayed with a hand against her side to support her prominent belly. She is flanked by two angels, who are holding open the curtains of a pavilion decorated with pomegranates, a symbol of Christ's Passion. The upper part of the painting is lost. The two angels are specular, as they were executed by the artist using with the same perforated cartoons.
The theological symbolism behind the representation is complex. Maurizio Calvesi has suggested that the tent represents the Ark of the Covenant. Mary would be thus the new Ark of Alliance in her role as Mother of Christ. For other scholars the tent is a symbol of the Catholic Church and the Madonna would symbolize the tabernacle, as she is portrayed containing Jesus' body.