Washington DC - Donald Trump was back on the campaign trail Friday amid upheaval brought on by his apparent ditching of right-wing positions on reproductive rights.

The Republican presidential candidate will appear first in the battleground state of Pennsylvania for an afternoon rally, before heading to the capital Washington to speak to the powerful conservative parental rights group Moms for Liberty.

The stops come as the billionaire takes fire from both his Democratic rival, Kamala Harris, and much of his conservative base over his recent tack towards abortion access and fertility treatments such as in-vitro fertilization (IVF).

Trump has said his administration would be "great" for reproductive rights, promised to mandate free IVF treatments for those who want them, and on Thursday suggested that he would vote to overturn Florida's ban on abortions after six weeks' pregnancy, which he called "too short."

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His campaign quickly walked the Florida comments back, saying Trump did not actually specify how he'd vote when a referendum takes place in his home state in November.

But combined with his long-shifting position on abortion – and a Republican Party platform that has dropped calls for a national ban on the procedure – the comments have drawn conservative fire.

The Harris campaign pressed the attack Friday.

"The majority of Americans support abortion access, they support IVF, they support contraception. He has finally figured it out, and he'll do anything to distract from his abysmal, horrifying record on this issue," Mini Timmaraju, the president and CEO of advocacy group Reproductive Freedom for All, told reporters in a campaign call.

Harris surrogate Senator Elizabeth Warren told the same call that Trump – who stacked the US Supreme Court with justices who overturned the constitutional right to abortion in 2022 – had "opened the door for any extremist judge or extremist state legislature to ban IVF."

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Trump's running mate JD Vance dismissed the same idea on CNN as "a ridiculous hypothetical."

But earlier this year a court in Alabama ruled that frozen embryos could be considered a person or child, causing fertility clinics in the state to briefly pause IVF treatments in light of the new legal risks.

A majority of Americans say they want access to abortion, and the Supreme Court's decision to return power over the procedure to the states has seen voters turn out in state, local, and national elections to back Democrats, who have vowed to reinstate the right.

Trump's recent pivots have drawn accusations that he has abandoned the anti-abortion movement, largely made up of evangelical Christians and hard-right conservatives who for decades have formed one of the most motivated voting blocs in the Republican Party.