TUESDAY, July 23, 2024 (HealthDay News) -- There's a slight but significant rise in dangerous obstetric complications for pregnant women who use marijuana, new research shows.

Data from almost 317,000 pregnancies in women in California found those who used the drug had higher odds for gestational hypertension, preeclampsia, weight gain that goes beyond recommended levels and a condition known as placental abruption (when the placenta separates from uterine wall).

The researchers said the findings are important since "little is known about whether prenatal cannabis use is associated with maternal health outcomes during pregnancy."

The study was published July 22 in the journal JAMA Internal Medicine.

Numerous studies have suggested that the use of cannabis during pregnancy can raise fetal risks for low birth weight, preterm birth and the need for care in a neonatal ICU.

Nevertheless, some women "report using cannabis to help with sleep, depression, stress, morning sickness and pain during pregnancy, and many perceive cannabis to be a safer alternative to prescription medications," wrote a team led by Kelly Young-Wolff, of Kaiser Permanente Northern California.

To find out how marijuana use might affect moms-to-be, the Kaiser team looked through the medical records of more than 250,000 pregnant women living in northern California (some with multiple pregnancies recorded).

The women's level of marijuana use while pregnant -- none, or use daily, weekly or monthly -- was either self-reported or gleaned through toxicology testing.

Overall, 6.3% of the women in the study did use cannabis at some time during their pregnancy, although only a small minority said they used it on a daily (0.6%) or weekly (0.7%) basis.

Prenatal cannabis use was tied to a small but significant rise in a variety of obstetric complications, the study found.

For example, the practice raised a pregnant woman's odds for gestational hypertension (high blood pressure occurring while pregnant) by 17%, and her odds for an even more dangerous blood pressure condition, preeclampsia, by 8%, Young-Wolff's team reported.

The link to gestational hypertension was a dose-response relationship: the more often a woman used cannabis, the higher her likelihood of high blood pressure during her pregnancy.

Women who used marijuana also faced a 19% higher odds for placental abruption, which can jeopardize the flow of oxygen and nutrients to the fetus.

Marijuana use also upped the odds that a woman would gain weight during her pregnancy at a rate that was either higher or lower than that recommended.

There was one outlier to the findings: Women who used marijuana while pregnant appeared to have a slightly lower risk of developing gestational diabetes.

The exact reasons for that trend aren't clear, the Kaiser team said, but there seems to be "a complex association between prenatal cannabis use and maternal health."

Going forward, it's clear that what's needed is "non-stigmatizing care and education to support pregnant individuals in making informed decisions about cannabis use," Young-Wolff's team said.

More information

Find out more about cannabis use in pregnancy at the March of Dimes.

SOURCE: JAMA Internal Medicine, July 22, 2024