On their first date, Patrick and Dorothy Yeung talked at a Mexican restaurant for six hours. They even discussed marriage, and found they shared a desire for “as many kids as God would give,” Patrick says.

But four years into the Yeungs’ marriage, Dorothy still hadn’t conceived, although she and her husband yearned for children.

Doctors told the St. Louis, Mo., couple that their only hope for biological children was in vitro fertilization (IVF), a process they opposed as Catholics. The Yeungs began to pursue adoption, but still wanted answers about their infertility.

Patrick, who is now an OB-GYN and fertility specialist, learned about an IVF alternative called “NaProTechnology,” short for “natural procreative technology,” also referred to as “restorative reproductive medicine.” Catholic doctor Thomas Hilgers founded the method in the mid-1980s after the Vatican denounced artificial insemination and the creation of test-tube babies. It relies on meticulous tracking of a woman’s menstrual cycle, diagnostics, and treatments that address the underlying causes of infertility. The treatments range from supplements and hormonal therapy to surgery to restore female reproductive organs impeded by abnormal growths, blocked fallopian tubes, or ovarian dysfunction.

Despite little fanfare and sometimes daunting protocol, NaProTechnology is quietly gaining a following as many infertile couples seek an alternative to IVF.

One in 8 couples has trouble achieving and sustaining pregnancy, and 12 percent of U.S. women under the age of 45 have sought fertility treatment, according to the Centers for Disease Control and Prevention. In a booming fertility industry dominated by IVF services, doctors often push infertile couples toward assisted reproductive technology as their only option for biological children.

Sometimes this leaves the cause of infertility unexplained and untreated. It can also leave couples hopeless if, like the Yeungs, they opt out of IVF for religious and ethical reasons. Many couples have become concerned about IVF practices, including the freezing of surplus embryos, selective reduction, and screening procedures that weed out “abnormal” embryos. One clinic in Fort Worth, Texas, promotes NaProTechnology as a “morally acceptable system which maintains the integrity of the person.”

But others are drawn to NaProTechnology simply because IVF is invasive and expensive: The average cost of an IVF cycle (often not covered by health insurance) is $12,000, with only about 30 percent of women giving birth to a healthy baby with just one round. In contrast, NaProTechnology often leads to a “billable diagnosis” of a medical condition likely covered by insurance, Patrick says.

Looking for answers, Dorothy began charting her female cycle and had an exploratory surgery to find out why she couldn’t conceive. A laparoscopy revealed she had severe endometriosis, one of the top three causes of female infertility. After surgical treatment, doctors showed Dorothy her “obliterated ovaries” and she “cried for weeks,” believing her chances for biological children were gone. That same year, the Yeungs adopted a baby girl.

But the Yeungs were shocked six months later when Dorothy found she was pregnant. They’ve since had three children naturally. Patrick, a “restorative fertility” specialist at Saint Louis University, shares their story with his patients: “You can’t guarantee a baby. ... But we can set the table and see what happens.”