Some couples struggle to get pregnant again after having a baby. What to know about secondary infertility.

For many people who have already given birth, deciding to try for a second child comes with the assumption that pregnancy will be inevitable. After all, they successfully became pregnant before, so why not again?

But according to the Cleveland Clinic, 11% of American couples experience secondary infertility, which is roughly the same percentage of those enduring primary infertility, or the inability to conceive their first child successfully. As National Infertility Awareness Week gets underway, experts explain how secondary infertility is diagnosed, what might be causing it and why it's important to have more awareness and understanding of the challenges some people face as they try for another baby.

What is secondary infertility?

The diagnosis of secondary infertility is given to couples who have successfully conceived without medical intervention in the past, regardless of whether or not that pregnancy resulted in a live birth. The successful first conception must have occurred without any assisted reproductive technology or fertility medications.

According to Dr. G. Thomas Ruiz, lead ob-gyn at MemorialCare Orange Coast Medical Center in Fountain Valley, Calif., patients who have not had success in getting pregnant a second time after having unprotected sex for a year are considered to have secondary infertility. “For a normal, fertile couple, the probability of a pregnancy when the timing is right is anywhere from 15 to 18% depending on the patient’s age. By the end of a year, 90% of couples would have had a pregnancy within a year’s time,” Ruiz tells Yahoo Life.

What causes it — and what can be done?

Ruiz says that there are a number of causes contributing to secondary infertility, ranging from age-related issues to reproductive-organ scarring associated with a variety of illnesses. The male partner is typically tested before any further investigation of the woman to rule out low sperm count or other semen-related issues. “A lot of the time, it’s a different partner than their first pregnancy,” Ruiz notes. “They had kids, got divorced, have a new partner and he wants kids.”

Women may also be experiencing a lack of ovarian reserve, since they are born with a finite number of eggs. Other factors may be polycystic ovary syndrome (PCOS), endometriosis, pelvic inflammatory disease or other, less common conditions that can cause scarring, making conception difficult.

Treatment depends on the root cause of infertility and, according to Ruiz, can vary based on a patient's age and other factors. “In terms of treatment, we take a history, do cervical cultures to make sure there’s not an underlying infection — usually a pelvic ultrasound — get a detailed surgical history because if they had a procedure that causes scar tissue that would certainly have a negative effect,” he explains. “Then you may do things like ... check tubal patency [to see whether the Fallopian tubes are blocked], which involves injecting dye into the uterus.”

For older patients, Ruiz recommends spending less time on diagnostics before referring patients to a reproductive endocrinologist to discuss intrauterine insemination (IUI) or in vitro fertilization (IVF). Ruiz says, “Sometimes the secondary infertility is just because they are now 40 years old and trying to get pregnant.”

What it's like to deal with secondary infertility

Amy Klein, the author of The Trying Game: Get Through Fertility Treatment and Get Pregnant Without Losing Your Mind, tells Yahoo Life that going through secondary infertility after easily getting pregnant the first time around can come as a shock. The experience can feel frustrating and isolating — especially given the reactions from others that some women have received. “There’s an added sense of guilt, like this feeling you should be happy with what you have, or people telling you to be grateful that you have one [child] and to just enjoy that one instead of focusing on having more,” Klein says.

Klein has experienced this firsthand. When she was struggling to have another baby, people told her to just be grateful she was married. “I think if a woman has one child and wants a second, or has two children and still wants another, she shouldn’t feel guilty,” she says. “She should do what it takes to get there, and if it’s too hard, she can also feel OK stopping.”

But seeing celebrities — including astronaut and mom-of-one Kellie Gerardi and Married at First Sight star Jamie Otis, who is pregnant with twins after spending three years trying to give her son and daughter another sibling — open up about their own experiences with secondary fertility is refreshing, Klein says.

"When celebrities or public figures talk about their infertility, it helps destigmatize the subject — especially with secondary infertility," she says. "It’s nice to see them being so open about their journeys.”