JD Vance is accusing Tim Walz of lying about using in-vitro fertilization, or IVF, to have children − and the back-and-forth raises important points about the differences between IVF and intrauterine insemination, or IUI.

On X Tuesday, Vance, the Republican vice presidential candidate, wrote: "Today it came out that Tim Walz had lied about having a family via IVF. Who lies about something like that?" Vance also shared an interview clip of Walz in which he says that, if it were up to Vance, he "wouldn't have a family because of IVF and the things that we need to do reproductively."

Vance's post comes after a Glamour magazine article Monday, in which Walz's wife Gwen shared she conceived via IUI. Tim and Gwen Walz have two children: daughter Hope, 23, and son Gus, 17.

Gwen said in the article that recent legislation restricting IVF inspired her to speak out about how fertility procedures have impacted her. "After seeing the extreme attacks on reproductive health care across the country — particularly the efforts in Alabama that jeopardized access to fertility treatments — Tim and I agreed that it was time to formally speak out about our experience," she said.

What is the difference between IUI and IVF?

IUI and IVF are not the same. The biggest difference between them is that the former involves egg fertilization inside the body while the latter happens outside.

IVF begins with patients taking medication to stimulate ovary follicle growth, gynecologist Dr. Karen Tang previously told USA TODAY. Doctors then conduct a procedure to retrieve those eggs, during which they put the patient under anesthesia and use a long, thin needle that's inserted through the vagina.

Following this procedure, medical professionals fertilize the eggs with sperm. Then the "resulting embryos are grown and evaluated for appearance and quality," Tang added.

What is IVF?Explaining the procedure in Alabama's controversial Supreme Court ruling.

In some cases, the embryos are tested genetically, such as if one of the patients is a carrier for a serious medical condition or if they've experienced several miscarriages. The "highest quality embryos are then transferred into the uterus," Tang said.

IUI, on the other hand, may or may not require medication for follicle growth, Tang noted. Gwen Walz described to Glamour how a neighbor who was a nurse helped her administer "the shots I needed as part of the IUI process.” ("She would give me the shots to ensure we stayed on track.”)

Instead of IVF's process of retrieving eggs, fertilizing them outside of the body and re-inserting them back into the body, IUI involves inserting sperm directly through the cervix into the uterus, fertilizing the egg inside the body.

While Tang noted IVF has a higher average success rate than IUI, that doesn't mean there's a guarantee of getting pregnant the first time around with IVF.

Why is IVF controversial?

It's common in IVF procedures for unused or low quality embryos to be discarded, which is why the procedure is heavily criticized by some pro-life advocates. In February, the Alabama Supreme Court ruled that embryos created during IVF are legally protected like any other child. Alabama's constitution protects unborn children, which legally typically refers to a fetus in utero.

So why can't doctors create and transfer one embryo at a time to avoid having to store or discard embryos during IVF? Tang said it's all about giving patients their best chance at getting pregnant.

More:Lala Kent of 'Vanderpump Rules' is using IUI to get pregnant. What is that?

How long does IUI take to get pregnant?

The short answer: It depends. But the actual process of IUI has less steps than IVF.

IUI has a lower average success rate than IVF, so people may go through more cycles of IUI than IVF, Tang said. Cost can also be a deterrent in trying multiple rounds of IVF. The estimated average cost per IVF cycle is about $12,000, according to the American Society for Reproductive Medicine (ASMR). But Tang noted it can wind up a tab as much as $25,000 or more.

Contributing: Hannah Yasharoff