Mothers who smoke marijuana while nursing their child transfers a small amount of cannabis's psychoactive ingredient in the breast milk, a new study finds.

Researchers, from the Texas Tech University Health Sciences, conducted a controlled study of eight anonymous nursing women who regularly use marijuana. The purpose of the study is to determine if the breast milk samples will test positive for Delta-9-tetrahydrocannabinol or THC.

The milk samples were tested 20 minutes after ingestion, followed by one, two, and four hours post-ingestion state. It was given to infants aged three to five months.

The study, published in the journal Obstetrics and Gynecology, showed that approximately 8 micrograms of THC per kilogram per day were present in the milk. It translates to about 2.5 percent of the amount of THC the mother took.

Controlled Intake

Lead author Dr. Tom Hale, a professor of pediatrics and the executive director of InfantRisk Center, said that not all of the THC content will be absorbed by the baby.

"The levels are low in the milk, and even less would be absorbed by the infants," Hale said.

Experts said it would usually take two hours for the body to absorb THC and at least 20 hours to be expelled. However, the study warrants further investigation due to the absence of blood work.

The researchers said collecting blood samples would add a whole new perspective to the study because then, they will be able to identify and measure THC levels.

Hale said what sets their study apart from others is that they have controlled the amount of cannabis given to the participants. Each subject smoked 0.1 gram of marijuana with 23.18 THC concentrations.

Lower levels of cannabis were given after examining previous studies where participants smoked 0.6 of cannabis with 3.55 percent of THC.

"The study was carefully controlled. We knew exactly what they smoked and when they smoked it," Hale said.

Neurological Effects

Hale emphasized that although they were able to measure the THC level in breast milk, the study did not explore its effects on the child's neurological development.

Dr. Ronald Marino, chief of the pediatrics division at NYU Winthrop Hospital in New York, said that although the study showed minimal THC exposure, it is best for babies not to acquire this ingredient.

"Your baby's brain is developing so much in the first year of life, you want to give them every chance to have a high function. Try to stay as pure as you can when breastfeeding - [avoiding] marijuana, alcohol or even herbal remedies," Marino said.

More than a dozen states in the United States have legalized the use of cannabis for medical and recreational purposes. Just like alcohol, Hale said marijuana is not advisable for pregnant or nursing women even if the law allows its use.

The American College of Obstetricians and Gynecologists also discourages the use of marijuana among pregnant and breastfeeding women due to its unknown effects on the mother and the child.

"[B]ecause of concerns regarding impaired neurodevelopment, as well as maternal and fetal exposure to the adverse effects of smoking, women who are pregnant or contemplating pregnancy should be encouraged to discontinue marijuana use," ACOG advised.

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