U.S. initial public offering activity increased in the second quarter compared to a year-earlier period, according to a report released Tuesday by PricewaterhouseCoopers. For the three months ended June 30, 39 IPOs raised $5.1 billion compared to only 12 IPOs that raised $1.6 billion on U.S. exchanges a year earlier, the report said. Of the IPOs in the most recent period, 20 were staged on the New York Stock Exchange and 19 on NASDAQ. IPO activity in Houston was on pace with the increased number of deals completed during the quarter. Four energy IPOs came to market during the second quarter, starting off in April with Missouri City-based Global Geophysical Services (NYSE: GGS) raising $90 million. Three Houston-based companies followed up with offerings, each one raising more money than the others: PAA Natural Gas Storage LP ( $216 million); Niska Gas Storage Partners LLC (NYSE: NKA) ( $359 million) and Oasis Petroleum Inc. (NYSE: OAS) ( $676 million). However, skittish market conditions saw the total number of U.S. IPOs decline during the three consecutive months during the quarter: 17 companies came to market in April and 11 in May and June. PricewaterhouseCoopers noted that another 15 IPOs were postponed or withdrawn in May and June, showing hurdles to entering the market still exist. â¿¿While recent market swings have posed a short-term threat to companies looking to price their IPOs, the path to a successful IPO is a journey â¿¿ not a sprint,â¿ said Scott Gehsmann, capital markets partner with PricewaterhouseCoopersâ¿¿ Transaction Services. â¿¿Interim market challenges provide opportunities to reflect on the adequacy of the issuerâ¿¿s readiness to enter the public equity markets and the post-IPO strategic plan.â¿ Sixty-eight companies registered new IPOs during the quarter, and Pricewaterhouse Coopers expects small and mid-cap deals to continue to dominate the space.