The woman, 23, who has not yet been identified, was arrested with her husband in Montpellier, in the south of France.
Authorities arrested the couple after neighbours said the woman showed signs of becoming radicalised.
In a search of their home police agents found a prosthetic belly inside which was covered in tin foil.
Investigators have also said the woman told relatives that she wanted to “die a martyr.”
French counter-terrorism agents said the couple had “disturbing profiles,” according to the French media reports.
Officers searching their home allegedly confiscated material related to al-Qaeda and Islamic State (ISIS), also known as Daesh.
However, the woman claimed she bought the fake pregnancy bump on the internet so she could shoplift items from the department stores without raising alarm.
It comes as France continues to be on high alert following the Paris terror attacks on November 13 which killed 130 people. ISIS claimed responsibility for the massacre.
Earlier today an Islamic terror suspect who cut-off his boss’s head and pinned it to a fence at an industrial park killed himself in prison.
Yassin Salhi, 35, was found hanged in his cell while awaiting trial on suspicion of being an ISIS supporter.
The French government has described last month’s terror attacks as the worst atrocities on French soil since the end of the Second World War.
Global powers have vowed to take the fight to ISIS militants currently in control of parts of the Middle-East.
Earlier this month Prime Minister David Cameron won approval from parliament to conduct airstrikes targeting ISIS in Syria