Ms Reeves reportedly asked Mr Corbyn's office to intervene on her behalf, but was turned down.
Her case was also raised at Monday night's meeting of the Parliamentary Labour Party, as well as at Tuesday's meeting of the Shadow Cabinet.
Labour’s deputy Labour Mr Watson tweeted on Wednesday: "A small group of members are trying to bully another pregnant MP out of the Party.
"This reprehensible behaviour cannot be tolerated. We will not accept bullying and threats in our ranks. The entire shadow cabinet will want to publicly condemn this too.”
Shadow Health Secretary Jonathan Ashworth tweeted: “My friend Ellie Reeves is a socialist, an ex-trade union lawyer who fought against injustices for working-class people.
"She’s campaigned against oppression internationally, eg trade unionists in Colombia for years. An excellent MP. Ludicrous no-confidence motion should be binned.”
Mr Williamson's readmission the party lasted only 48 hours. He was readmitted was readmitted last Wednesday by a panelpanel that ruled he should only be reprimanded but was suspended again on Friday amid a growing backlash.
One MP told the JC: "I thought the left had reached a new low with the treatment dished out to Luciana (Berger).
“But it seems like they still haven’t learnt their lesson and now they are attempting to bully a second pregnant MP out of the party.”
Young Labour chair Miriam Mirwitch tweeted: “MPs who are pregnant or on maternity leave should be automatically reselected. It’s wrong when bosses sack workers who are pregnant or on maternity leave. The same applies to MPs.”
A Labour party source said: “No motion has been formally moved or tabled. And in any case, motions of no-confidence have no formal standing and do not result in trigger ballots.
"Any MP who is on parental leave will not undergo reselection processes until they return from leave.”
