Brooke Mueller hid two stints in rehab from doctors while she was pregnant.
The 36-year-old troubled star - who has four-year-old twins Bob and Max with 'Anger Management' star Charlie Sheen - is believed to have been battling an addiction to crystal methamphetamine while she was carrying twin boys and allegedly kept this from medical staff involved in the safe delivery of her children - who were born seven weeks early in March 2009.
A source told RadarOnline.com: "Brooke didn't tell her obstetrician that she had been to rehab twice while pregnant ... Not one member on her labour and delivery team knew she had been using crystal meth during most of her pregnancy."
Brooke and Charlie - who wed in 2008 - were both concerned that their children would be taken away from them if this was found out.
The source added: "At that point, Charlie was very protective of Brooke, and didn't say anything because they both had a real fear that the boys would be taken away from them and placed in foster care. Brooke was also extremely afraid of being criminally charged with child endangerment because of her drug use while pregnant, so nothing was said to anyone."
Charlie is believed to regret this decision and thinks it might have benefitted the children had Brooke's problems been known by staff.
This comes days after Brooke allegedly agreed to have her two young children tested to see whether they have "fetal alcohol and drug syndrome", which can cause mental and physical defects which can develop in a foetus due to high levels of alcohol consumption during pregnancy.
The source explained: "Charlie now recognizes that was a catastrophic mistake for several reasons. Perhaps if the boys had been taken away, that might have scared Brooke enough to get sober once and for all.
"Secondly, the boys would have been properly treated and assessed for fetal alcohol syndrome."