What is Roe v Wade and why could abortion soon become illegal in many US states?

Roe v Wade was the landmark Supreme Court case that legalised abortion nationwide in the United States in 1973.

It was brought by Texas woman Norma McCorvey, using the pseudonym Jane Roe, who was unmarried, pregnant and wanted an abortion, but was unable to legally procure one within the state at the time.

Forty-five years ago, states were able to set their own abortion laws and it was only legal to terminate a pregnancy in Texas if it presented a serious risk to the mother's life.

But Ms McCorvey was healthy and could not afford to travel to another state for the procedure.

She argued against the defendant, Dallas County District Attorney Henry Wade, that Texas laws were unconstitutional because they were vague and violated her right to privacy.

The Supreme Court found in her favour, seven to two, and established a new national framework for abortion that all states would have to adhere to.

What was the new framework?
The court ruled that:

In the first trimester: All women in the US should have the right to terminate a pregnancy, as abortions are relatively safe during the first three months and the foetus is still underdeveloped

In the second trimester: The government has the right to regulate but not ban abortions, as the risks associated with terminating a pregnancy become much greater after 12 weeks. However, the laws must be aimed at protecting the mother

In the third trimester: The government has the right to prohibit abortions, as the risks are greatest during the final three months and the foetus is more likely to be able to survive on its own outside the womb. However, a woman should be allowed to terminate a pregnancy if it poses a risk to her life

So what does this have to do with Brett Kavanaugh?
If confirmed, Judge Kavanaugh will replace Justice Kennedy, who was often the swing vote on key issues such as abortion and gay rights.

So if he's less receptive to abortion, experts say there will be enough conservative support within the Supreme Court to overturn the Roe v Wade decision and once again allow individual states to ban abortions outright.

Does Donald Trump know about this?
Yes, and it was likely one of the key reasons he named Judge Kavanaugh in the first place.

During his election campaign, Mr Trump said abortion should be largely banned in the United States, and he would appoint anti-abortion justices to the Supreme Court who would help overturn the decision.

So how likely is all this to happen?
Immediately after Justice Kennedy announced his retirement, CNN analyst Jeffrey Toobin appeared pretty certain Roe v Wade would be overturned.

And Elizabeth Ingleson, an honorary associate at the United States Studies Centre, agreed it was becoming very likely. She said the real question was how it would all play out.

"Any chance at blocking Mr Trump's nominee would require support from all Senate Democrats and two Republicans," she said.

"There is speculation that Republican senator Susan Collins may be one such senator to block his nominee, but even this is unlikely."

What states will criminalise abortion if Roe v Wade is overturned?
If Roe v Wade is repealed, Dr Ingleson said Louisiana, Mississippi, North Dakota and South Dakota had "trigger laws" which would immediately make abortion illegal.

And according to the Centre for Reproductive Rights, 19 other states would also have a high risk of losing abortion rights.

However, Dr Ingleson said nine states had laws that would explicitly protect abortion. They are: Washington, Nevada, California, Maine, Connecticut, Maryland, Delaware, Hawaii, Oregon.