The small-cap stock was down 28.47% to $8.14 a share.
Sientra lost 87 cents a share in the quarter, wider than analysts' calls for a loss of 67 cents. The company has missed earnings estimates in the last four quarters. Revenue was $19.02 million, beating estimates of $17.56 million. The operating loss in the quarter was $24.39 million.
CEO Jeff Nugent remained optimistic on the future as the company has innovated its breast products.
"Last year's accomplishments were pivotal to positioning Sientra for sustainable long-term growth across both our business segments," said Nugent. "I am encouraged by the progress we have made in establishing Sientra as a leading, diversified global partner to aesthetic physicians and I am looking forward to continuing this momentum in 2019."
Analysts at William Blair downgraded the stock to market perform from outperform.
Since reaching a level of $14.83 a share on Jan. 9, the stock has shed almost half of its value.