Sera Prognostics (SERA) said Monday it launched a proposed offering of its Class A common stock and pre-funded warrants to purchase the common stock.

The company said it intends to grant the underwriters a 30-day option to purchase up to an additional 15% of the total amount of shares sold in the offering.

Sera is offering all shares and warrants in this sale, though it has not yet disclosed the total size of the offering.

Proceeds from the offering are expected to support the company's commercial expansion in the US, preparations for entry into the European market, and further research aimed at increasing adoption of its PreTRM test, which assesses the risk of spontaneous preterm birth in certain pregnancies.

Shares of Sera Prognostics were down nearly 7% in after-hours trading.