Spot bitcoin exchange-traded funds (ETFs) in the U.S. recorded their 13th consecutive day of net inflows on Thursday, bringing in $48.71 million. Significant fund movements were noted in bitcoin funds from Fidelity, Ark Invest, and 21Shares.

Fidelity's FBTC led with $119 million in net inflows, while Ark's ARKB experienced nearly $100 million in net outflows, marking its largest outflow since its January debut, according to SoSoValue data.

BlackRock's IBIT, the largest spot bitcoin fund by net assets, recorded $2 million in net inflows. Grayscale's GBTC, now the second largest, saw no flows. Bitwise's BITB added $26 million, while Invesco and Galaxy Digital's bitcoin ETF each reported $2 million in net inflows.

Rachael Lucas, Crypto Analyst at BTC Markets, explained to The Block that these unusual flows are influenced by investor uncertainty regarding the Federal Reserve's interest rate decisions, particularly ahead of major economic reports from the U.S. on May 31. If U.S. inflation exceeds expectations and personal income and spending rise, it could reduce investor optimism about a potential Fed rate cut in September, negatively impacting demand for riskier assets like bitcoin and related ETFs.

Over the past 13 days, U.S. spot bitcoin ETFs have seen total net inflows exceeding $2 billion, their second-longest positive streak since their listing, following a 17-day streak that began in January. However, the total volume of flows remains significantly lower than the peak seen in March, according to The Block's data dashboard.

Meanwhile, Grayscale filed an amended S-1 registration statement for its spot Ethereum fund on Thursday, a day after BlackRock’s filing. More S-1 filings are expected as the SEC has asked issuers to submit their forms by Friday.