Around 1.7% of women ages 15 to 49 years old have tried a procedure called artificial or intrauterine insemination to start a family, the most recent data from the Centers for Disease Control and Prevention suggests.

Among them was the wife of Minnesota Governor Tim Walz, the running mate of Vice President Kamala Harris, as part of what she describes as an “incredibly personal and difficult experience.”

“The only person who knew in detail what we were going through was our next door neighbor. She was a nurse and helped me with the shots I needed as part of the IUI process,” said Gwen Walz in a statement shared by a campaign spokesperson.

The Walzes have two children, Hope, 23, and Gus, 17.   

The Trump campaign has accused Walz of lying about starting a family with another type of fertility treatment called in vitro fertilization, or IVF.

IVF has become a key campaign issue amid calls from groups like Susan B. Anthony Pro-Life America for Republican-led legislatures to tighten restrictions and state laws that threatened to curb access to this fertility treatment. 

Congressional Democrats have also petitioned to force a bill prohibiting limits on IVF nationwide out of a House committee, in hopes of bringing it to a vote.

What has Tim Walz said about his family and IVF?  

Before this week, Walz has discussed the infertility treatments undergone by his wife as being “like IVF.” 

“Gwen and I have two beautiful children because of reproductive health care like IVF,” Walz wrote on Facebook after a ruling by the Alabama Supreme Court determined that embryos created through IVF should be considered children, which potentially subjects them to laws governing the wrongful death of a minor. “This issue is deeply personal to our family and so many others. Don’t let these guys get away with this by telling you they support IVF when their handpicked judges oppose it.” 

The Harris campaign defended the times Walz suggested their family had used IVF, saying he “was using commonly understood shorthand for fertility treatments” and that “attacks on reproductive rights are putting all fertility treatments at risk.”

“The Trump campaign’s attacks on Mrs. Walz are just another example of how cruel and out of touch Donald Trump and JD Vance are when it comes to women’s healthcare,” said Mia Ehrenberg, a spokesperson for the Harris-Walz campaign.

Why are there objections to IVF but not IUI?

IUI works by collecting semen from the male partner, which is then cleaned and concentrated. Then when the female partner is ovulating, the provider can insert the semen into the uterus using a catheter, improving the chances that sperm can reach the egg. 

By contrast, IVF involves a number of steps to take eggs out of a woman and fertilize them in the laboratory with sperm from a man. 

The Southern Baptist Convention voted earlier this year to condemn “the way IVF is routinely conducted now,” echoing calls from other groups for bans on “practices which encourage couples to harvest and fertilize more eggs” than they plan to use.

“Though it does not necessarily occur in the womb, the willful destruction of fertilized embryos conducted in the typical practice of IVF is not theologically different from abortion,” the church’s Ethics and Religious Liberty Commission wrote.

Meanwhile, IUI has not drawn the same outcry from some abortion rights opponents. While fertility treatments used in IUI yield more eggs, that results in a higher chance of multiple pregnancies — for twins or more.

Denominations like the Lutheran Church Missouri Synod that have rejected other approaches like surrogacy have not objected to IUI.

“Artificial insemination is implicitly accepted, given that the sperm and egg belong to the married man and woman, but it is viewed with some skepticism as adults may be tempted to use this method in lieu of addressing other underlying issues,” Emma Waters of the Heritage Foundation wrote earlier this year. 

How are fertility medications used in IUI?

Fertility medications like the ones Gwen Walz mentioned in her statement are also commonly given in hopes of improving the chances of success with IUI, either as oral medications or injections.

Common options to produce this “ovarian stimulation” are either tablets of clomiphene citrate or treatment using shots of hormones called gonadotropins to make more eggs.

These shots generally work over a few days to stimulate the growth of eggs, followed by a shot of another kind of hormone to “trigger” ovulation to begin.

Patients can prepare and inject shots themselves at home, though the Food and Drug Administration approved the first premixed injection pens in 2004 as an alternative.

Why do some choose IUI over IVF?

IUI is often a “first-line treatment option” offered by providers for couples struggling to have a child around the world, though success rates are lower than with IVF. The procedure is less invasive or costly than IVF and usually painless.

Average costs of IUI can be up to $2,000 per cycle, the Society for Assisted Reproductive Technology says, lower than the around $11,000 or $12,000 that IVF can cost. Not all states require coverage of fertility services like IUI or IVF, according to the Kaiser Family Foundation. 

During each cycle, IUI can be successful as much as 20% of the time if the procedure is done monthly, the National Institutes of Health says. 

For most couples who fail to conceive after three or four cycles of IUI, the American Society for Reproductive Medicine recommends trying IVF – though experts have suggested that IVF could be a first-line treatment for some patients.