It has been a few years since there was an active market for digital health IPOs. But that's changed now. Chronic health care management company Livongo Health Inc. has raised $355 million in an IPO, following last month's $609 million public debut for health care workflow management software company Change Healthcare Inc.

IPOs in the United States may be lagging overall, but in med-tech we have seen a flurry of IPO activity, sparking some long overdue optimism regarding the health of the industry. Most recently, Natera, a California-based company, began trading (NASDAQ: NTRA) this past Thursday at $22.10 after pricing 10 million shares of its common stock at $18, the high end of the expected $17 to $18 range. Natera is a genetic testing company that develops non-invasive methods for analyzing DNA. ConforMIS, a Massachusetts-based company, also received a warm welcome from investors when it began trading last Wednesday (NASDAQ: CFMS) at...