American women are having only half as many babies as they did 50 years ago, but fertility technology is becoming a bigger and bigger business.

The big picture: The number of babies born per U.S. woman has dropped from 3.58 to 1.89 in the last half century. But women still want help getting pregnant — and answers about their health outside the doctor's office.

So dozens of companies are crowding a market projected to reach $30 billion in annual sales in five years, introducing tracking apps, wearable tech and at-home fertility tests.

• Andreesen Horowitz recently invested in Glow, a company that raised $23 million. Glow makes apps that track menstruation, fertility and pregnancy.
• Union Square Ventures put money in Clue, which makes a competing app and raised $29 million.
• Sequoia led funding for Maven, a virtual women's health clinic.

Other innovators in fertility tech include Meet You, a Chinese fertility tracker app that doubles as a social network; Ava, a wearable device that tracks fertility through physiological metrics like body temperature and breathing rate; and Quanovate, a device that gives real-time feedback on a woman's fertility based on urine samples.

• "There's potential for this area to really grow," says Ja Lee, an analyst at CB Insights. "You have half the population that wants this, but there are not consumer-friendly solutions that are easy to understand."

Between the lines: Many younger women are using these new apps not to pursue pregnancies, but to avoid them, Lee says. "Even if they may not want to have kids ... it gives women info about their general health."

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