Thirteen people have been arrested over a trafficking ring which saw a pregnant woman tricked into visiting the UK before being sold into a sham marriage.

The 10 men and three women, aged between 24 and 57, were detained after police and Home Office officers went to their properties in Greater Manchester on Wednesday.

The offences for which they have been arrested include trafficking people for exploitation, conspiracy to facilitate breach of immigration law, and conspiracy to assist unlawful immigration into a member state. Three people were arrested for overstaying in the UK.

The pregnant victim was forced into marrying a man in Rochdale in July, having travelled to England two months earlier on the premise of visiting her sister in Luton. A man who met her at the airport purporting to be her sister’s friend was paid between £10,000 and £15,000 by the trafficking gang to arrange the sham marriage, police said. The victim, who was 25 weeks pregnant when she arrived in the UK in May, raised the alarm at a hospital where she had been taken to have an abortion.

Detective Inspector James Faulkner said: “This is a superb result following a long and complex investigation by GMP officers and our partner organisations. This woman was brought to Manchester with the sole purpose of being married to a man who hoped to boost his immigration status. She was completely unaware of this group’s nefarious motives and by the time she realised what was going on, it was too late.”

He said there were up to 400 cases involving women being trafficked for sham marriages in the Manchester area. “That is 400 women who were brought to this country on a false premise and trapped in relationships with men they do not know, 400 women enslaved by gangs only out to make money from their predicament,” Faulkner said.

“On top of that, Home Office statistics place a cost of £40,000 on the UK economy for each sham marriage. That is a potential cost of £16m to the city of Manchester in benefits, police and council resources and other costs – a gigantic sum especially when you consider the budget cuts affecting every single household in Greater Manchester at the moment.

“Modern slavery comes in many forms and this case is just one example of the reasons why vulnerable men and women are trafficked into this country. This investigation and subsequent arrests show that GMP and our key partners are committed to destroying modern slavery in Greater Manchester, by way of supporting victims, detecting and bringing offenders to justice or providing training to those who may be exposed to the crime as a third party.”