An Illinois woman faces at least 15 years in prison after pleading guilty to doping her 6-year-old twin girls with cough syrup and taking nude pictures of them with her boyfriend.

The 30-year-old mother pleaded guilty Wednesday in federal court in Wisconsin to creating child pornography. Her boyfriend pleaded guilty last month to sexually exploiting children. Both are due for sentencing in September.

The mother is pregnant, and U.S. District Judge Barbara Crabb ordered her placed at a prison medical center until sentencing.

The twins are living with their father. The pictures were taken at the woman’s home in west-central Illinois.