By: Yahoo Beauty, Korin Miller

Chrissy Teigen has been open and vocal about her struggle with fertility and her subsequent choice to undergo in vitro fertilization (IVF) to have children. And now, she’s tackling critics head-on who suggest that she took the easy way out.

On Monday, Teigen tweeted, “Since this is coming up again, I said our next baby would be a boy because that is the embryo we have left. A boy. So. Yeah.” Later a user, Linda Wampler, tweeted back at her, “did you give it a minute to try naturally or are you avoiding ‘the act?’ At least no political rants!” Teigen then replied, “Hi Linda, thanks for asking, you complete witch. I tried for about 9 years. Anything else, let me know!”

The initial tweet was in response to recent comments Teigen made to Entertainment Tonight about whether she’ll give her 9-month-old daughter, Luna, a sibling soon. “A little boy is next, for sure,” she said, confirming that she and husband John Legend “have a boy on ice.” Teigen also told Extra that the couple may try to get pregnant again the spring. “[John] goes on tour, I think, all of May, so after that, I guess,” she said, adding that her future baby is “literally like, ‘Please unfreeze me.’”

About 6 percent of married women in the U.S. have difficulty getting pregnant after a year of trying — the clinical definition of “infertility” — and 12 percent of women ages 15-44 have difficulty getting pregnant regardless of their marital status, according to the Centers for Disease Control and Prevention (CDC). IVF is the most common and effective type of assisted reproductive technology, the CDC says.

Allison K. Rodgers, MD, a board-certified reproductive endocrinologist at Fertility Centers of Illinois, tells Yahoo Beauty that IVF is rarely the first thing couples opt for when they’re trying to have a baby. “It’s an option of last resort when other options are not working or have a very low chance of success,” she says. “We all would rather have intercourse to make a baby instead of having it helped along in a lab.”

Mark Surrey, MD, founding partner and medical director of the Southern California Reproductive Center, tells Yahoo Beauty that most people actually wait too long to undergo IVF. “IVF is a very effective and rapid way for many people to have successful outcomes,” he says. “We don’t see many people until they’ve been trying for many years, and then they get older and the IVF process becomes more difficult.”

But IVF doesn’t guarantee success.  A 2015 study published in the journal JAMA tracked nearly 157,000 women undergoing IVF and found that the chance of having a baby on the first attempt was 30 percent. That number was consistent until the woman’s fourth attempt, when the success rate began to rise. By the sixth attempt, the odds increased to 65 percent.

Laurence Jacobs, MD, a reproductive endocrinologist at Fertility Centers of Illinois, tells Yahoo Beauty that women typically try to conceive without reproductive aid for six months to two years before finally turning to IVF. And, he says, IVF is not the “easy way to go.” “It involves weeks of preparation, followed by two weeks of shots and bloating and swelling, followed by egg retrieval which can be uncomfortable afterward,” he says. “Stress level is very high.”

Tina Koopersmith, MD, a fertility doctor and founder of West Coast Women’s Reproductive Center, agrees, telling Yahoo Beauty that IVF is “not an easy process.” “The woman has two weeks of daily shots — on some days two to four, or even five shots per day,” she says. “The woman also needs to come to the doctor every other day or every day to have ultrasounds and blood drawn.” A patient also has to go into an operating room, have anesthesia, and then undergo a surgical procedure to remove her eggs. “Eventually, either that month or the next month, the embryo is transplanted back to the uterus — another procedure day,” she says. “So as you can see, IVF is intensive, time consuming, and procedure-heavy.”

Jacobs says that of his 37 years in practice, less than 1 percent of his patients skip everything else and go straight to IVF without trying treatment options, unless they’re age 40 or older.

Rodgers notes that she had two babies without IVF and one baby with the procedure, and that all of her children are equally valid no matter how they were conceived. “I always joke that I don’t know which of my kids are the bigger miracle — the ones I needed to work so much for or the ones I didn’t,” she says.

Teigen’s openness about undergoing IVF is important for erasing the stigma behind the procedure — and several of her fans who had undergone IVF thanked her in her latest Twitter exchange. Surrey also points out that it really doesn’t matter how a woman conceives — all pregnancies are “normal.” “This technology is only a way to identify errors in human reproduction,” he says. “It does not change the normalcy of the process.”