FORTUNE — Dear Annie: I was half-heartedly looking for a new job, but now I’m stepping up my search. The last straw was spending Mother’s Day at the office, because of looming trial deadlines at the law firm where I work.

When I took this job right out of law school four years ago, the partner who hired me assured me that I’d have flexible hours and would be able to get home to see my son — who was two years old at the time — in the evenings and on weekends. It hasn’t worked out that way. I believe the firm’s intentions are good regarding work-life balance, but when push comes to shove, everyone here works around the clock, and ducking out “early” (say, 9 p.m.) means letting the team down.

I know there is lots of information online about family-friendly companies, but how do I know it’s accurate? I’m expecting a second child, and I’d like to avoid making the same mistake again in choosing my next employer. — Once Burned

Dear OB: As you may know, you’ve got plenty of company. Nearly three-quarters (71%) of women with kids under 18 are in the workforce now, according to the Bureau of Labor Statistics, and many of them have small children: 64% of moms with children under six years old are working outside the home, as are 57% of women with infants under a year old.

It’s no wonder, then, that many companies see promoting their efforts to accommodate parents as a boon to recruiting and retaining talent and, as you note, the ones with stellar reputations in this regard are pretty easy to find.

For instance, Fortune’s own annual Best Companies list features a ranking of the 10 best employers for work-life balance. Working Mother magazine has been publishing a yearly list of the most family-friendly employers for 25 years, taking into account such perks as telecommuting, flextime, and job sharing. Two companies, IBM (IBM) and Johnson & Johnson (JNJ), have made that list every year for the full quarter century.

Great, but like most things, family-friendliness is relative, if you’ll pardon the pun. Consider: Just last week, career site Glassdoor.com came out with the results of a poll identifying the best 25 U.S. employers for work-life balance. The top three: Nestle Purina PetCare, MITRE, and SAS Institute.

Yet even among those 25 winners, there are signs that parents — especially new moms — may be struggling. Only one in 10 employees in Glassdoor’s survey, for example, reported that they have the option to return to work gradually after childbirth or adoption.

In the job market as a whole — particularly since the recession, with its attendant waves of layoffs — finding a truly family-friendly spot can be like looking for the proverbial needle in a haystack.

Daniel Greenberg, chief marketing officer at job-search portal SimplyHired, notes that many companies know job hunters want a life outside the office, and have worded their job postings accordingly.

Since 2009, Greenberg says, SimplyHired has seen a 100% jump in the number of job ads containing the word “flexibility,” and a 166% leap in those mentioning telecommuting.

Even so, SimplyHired’s analysis shows that, of the 5.3 million U.S. job listings currently on the site (8 million worldwide), “only about 5.4% are mom-friendly,” says Greenberg. To help people like you pinpoint those jobs, the site developed algorithms that work in part by parsing job ads for family-friendly keywords and created a handy tool that allows you to narrow your search to just those jobs.

The most telling feature on SimplyHired, though, is a link labeled “Who do I know?” that connects to LinkedIn and Facebook and shows a list of job postings at companies where you already have social-media contacts.

“Current employees are the most reliable source of information” for getting the straight skinny on how family-friendly an employer really is, Greenberg notes. Anybody can toss the word “flexibility” into a job ad, after all, but if someone you know on LinkedIn tells you she hasn’t been home in time to tuck her kids into bed in months, beware.

Beyond that, Greenberg has a couple of suggestions for you. First, if you haven’t already done so, try sitting down with higher-ups at your firm and expressing your dissatisfaction with your workload. “Getting more flexibility depends partly on your status in the company. “Stars” have more leverage. But in general, directness is worth a try,” he says.

Before you embark on a full-scale job search, “try to work something out,” Greenberg adds. “Employers really value experienced people, and they would rather not have to replace you. So it may be a lot easier to negotiate more work-life balance where you are now than to go somewhere else where no one knows you — and where you may end up putting in long hours, at least at first, to prove yourself.”

And second, in sounding out prospective employers for flexibility, Greenberg adds, choose your words with care: “Tread lightly on asking directly about long hours. You don’t want to give the impression that your work ethic is lacking. But it is okay to ask about the company culture and especially about what a typical work day entails.” It also couldn’t hurt to request an informal meeting (maybe over lunch, away from the office) with a potential coworker or two, just to see what insights you can gather.

One more thought: You don’t mention whether you’re contemplating moving to another law firm or broadening your search to include other kinds of companies. When it comes to work-life balance, a few law firms do get it. A good source of detailed information about some of them: “When Work Works,” a guide to family-friendly employers from the Families and Work Institute and the Society for Human Resource Management.

Neveretheless, you might do better to cast your job search net as widely as possible, looking way beyond traditional law firms with their notoriously grueling schedules. A great book I’ve mentioned in this space before that might help spark some ideas for you is Deborah Arron’s What Can You Do With a Law Degree?: A Lawyer’s Guide to Career Alternatives Inside, Outside, & Around the Law.

Good luck!

Talkback: How family-friendly is your company? Have you ever changed jobs in order to get better work-life balance? Leave a comment below.