Pregnant women who use marijuana or breathe in second-hand smoke are up to 1.5-times more likely to have pregnancy complications, alarming study finds

Marijuana use or exposure to second-hand smoke during pregnancy significantly increases the risk of stillbirth and low birth weight, a study suggests.

Researchers from the University of Utah found that exposure to cannabis during pregnancy is associated with a 1.5-fold increased risk of low birth weight.

There was also a 30 percent increased risk of medically induced preterm birth, stillbirth and pregnancy-related high blood pressure in expectant mothers.

When a person ingests marijuana during pregnancy, tetrahydrocannabinol, also known as THC, and other chemicals pass to the baby through the mother's placenta, which provides nutrition and oxygen to the baby through the umbilical cord.

Dr. Robert Silver, professor of obstetrics and gynecology at the university, said: 'Cannabis use is not safe… you should not use cannabis during pregnancy.'

The researchers examined multiple urine samples from more than 9,000 expectant mothers across the country to obtain an accurate measure of cannabis exposure.

Using medical records, they then compared the marijuana exposure to the complications the baby suffered.

The researchers found that the more cannabis consumed, the greater the risk of negative consequences for the baby.

These include low birth weight, which is defined as a baby born weighing less than five pounds and which can increase the risk of stunted growth and cognitive development, as well as chronic disease and obesity later in life.

Other risks included premature birth, stillbirth and pregnancy-related high blood pressure in the women.

They found that overall the risk increased by almost 30 percent in those who used cannabis during pregnancy.

When the researchers looked at the results individually, they found a 50 percent increase in the risk of low birth weight.

Although there was a higher risk of stillbirth, admission to the neonatal intensive care unit, and neonatal complications and death, these associations were not statistically significant, meaning they may simply have been due to chance.

The research was published in JAMA.

About 24 states allow recreational use of marijuana and 38 states allow its medical use.

In some cases of miscarriage or stillbirth where the expectant mother used marijuana, they can be found guilty of “chemical endangerment of the fetus,” with a prison sentence of up to 99 years.

It adds to existing findings, including an extensive study conducted in Canada that found pregnant women who smoke cannabis have a 70 percent increased risk of having a baby with a serious birth defect and a 15 percent increased risk of stillbirth.

In 2013, the US government-run National Institutes of Health found a 2.3 percent increased risk of stillbirth among women who used cannabis during pregnancy.

Women who used marijuana during pregnancy were also 85 percent more likely to have a premature birth, which can lead to health complications down the road, including learning disabilities, vision problems and behavioral problems.

They may also have difficulty eating or gaining weight, and are more prone to respiratory problems or infections.

A 2022 study published in JAMA Pediatrics found that prenatal exposure to cannabis after five to six weeks of pregnancy is associated with attention, social, and behavioral problems that persist into early adolescence.

Cannabis is the most commonly used federally illegal drug among pregnant women in the United States, with use among this group doubling between 2002 and 2017, the latest year of data is available.

In some parts of the US, up to a quarter of pregnant women use marijuana during pregnancy, according to a recent study in the journal JAMA.