Three men, aged 53, 38 and 20 years old from the St Brides area of Newport, have been arrested on suspicion of slavery and servitude offences, Gwent Police said.
Four other suspects remain in custody and are assisting officers with their enquiries after the granting of a further 24 hours in custody by a District Judge.
More top news
The controversial procedure involved nuclear DNA from the mother, mitochondrial DNA from a donor, and the father's sperm.
The move comes amid a boycott of the paper in Liverpool due to its controversial coverage of the 1989 Hillsborough disaster.
Glasgow East MP Natalie McGarry has been charged in connection with alleged fraud offences.