This past March, a source exclusively told RadarOnline.com that Duff was desperate to have another child, and "begging" Koma to get her pregnant!
In December she spoke glowingly of reconciling with her beau.
Duff is already mother to her 6-year-old son, Luca, whom she shares with ex-husband Mike Comrie.
For his part, Koma, 31, shared the same photo, writing, "We made a baby girl!"
Former Lizzie McGuire star Hilary Duff, has some more exciting new on the horizon! "She will be as attractive and sweet as her mother", he wrote on Instagram, adding, "another incredible chapter begins".
Revealing she was back on with Matthew for the third time, Hilary said at the time: 'It's going so great'. "My new niece has arrived!" He's the best.' I'm like, 'I'm here. "She was like, 'I just love him". I exist, you know? "Third time's a charm!" during an appearance on The Talk. However, she hasn't always been so confident about showing it off.