Think you're fully covered for childbirth? Maybe you're not.

Having a baby is a common health event, yet insurance coverage isn't always assured.

Although the federal government recently clarified that many insurance plans must cover prenatal care as a preventive service without charging patients anything out of pocket, it didn't address a crucial - and much pricier - gap in some young women's coverage: labor and delivery costs.

Perhaps this shouldn't come as a surprise. Insurers and some employers have long tried to sidestep paying for maternity care, which includes prenatal, delivery and postpartum services. Individual plans typically refused to pay for pregnancy-related services until the health law established that maternity and newborn care must be included in individual and small-group coverage.

Large employers that provide health insurance are required to cover maternity care for employees and their spouses under the Pregnancy Discrimination Act of 1978. But that protection doesn't extend to dependent children, even though children can now stay on their parents' plans until they turn 26.

"I suspect that a lot of this goes back to 'dependents' being kids," says Adam Sonfield, a senior public policy associate at the Guttmacher Institute, a reproductive rights research and education organization. "That perspective is just outdated, and was never entirely correct in terms of need for care anyway."

In May, the federal government specified that dependent children are covered by the health law requirement that preventive services, including preconception and prenatal care, be covered without cost sharing in all plans, except those that were grandfathered under the law.

Typically, prenatal care for a first pregnancy would include visits to her health care provider every four weeks for the first 28 weeks of pregnancy, then every two weeks until 36 weeks and weekly thereafter, according to the American Congress of Obstetricians and Gynecologists. In addition, the U.S. Preventive Services Task Force recommends pregnancy-related services, including screening for gestational diabetes, anemia and hepatitis B.

But prenatal care is a small portion of the cost of having a baby, and families that have to pay for an adult child's labor and delivery charges, including the hospital bill, could be on the hook for thousands of dollars.

Insurers paid $18,329 for a vaginal birth and $27,866 for a Caesarean birth, on average, in 2010, according to a study by Truven Health Analytics. Consumers paid an average of $2,244 and $2,669, respectively, out of pocket. The payment totals include all maternity care.

Hospitalization made up between 81 and 86 percent of the total cost of maternity payments, the study found. Prenatal care accounted for most of the remainder.

"The payments that are made are highly concentrated in that little window," said Carol Sakala, director of the Childbirth Connection, one of the organizations that commissioned the study. Childbirth Connection is a program of the National Partnership for Women and Families, an advocacy group.

But labor and delivery is exactly what some health plans don't cover for dependent children.

Continuing a slow upward trend, the average age at which women have their first baby was 26 in 2013. Meanwhile, the proportion of first births to teenagers continues to decline. In 2010, 19 percent of first births were to teenagers, compared with 36 percent in 1970.

Although the extent to which large-employer plans refuse to cover maternity care for dependent children isn't known, benefits experts say it's common.

In 2013, the National Women's Law Center filed sex discrimination complaints with the Office for Civil Rights of the federal Department of Health and Human Services against five employers that exclude pregnancy-related coverage for the dependent children of their workers.

The law center brought the complaints under a section of the health law that protects people from discrimination on the basis of sex, race, color, national origin, age, disability, gender identity and sex stereotypes.

"Pregnancy discrimination is, per se, sex discrimination," says Dania Palanker, senior counsel at the National Women's Law Center. The center is still awaiting a response to its complaints from the civil rights office.

The office said it can't comment on open cases or compliance reviews.

This column is produced through a collaboration between The Post and Kaiser Health News, an editorially independent news service that is a program of the Kaiser Family Foundation. To submit a question, go to kaiserhealthnews.org/contact-insuring-your-health.

WASHINGTON POST-BLOOMBERG - 06-30-15 1700ET