Women who have depression symptoms during pregnancy may be more likely to deliver early, a new study suggests.
Researchers found that of more than 14,000 pregnant women, those who screened positive for possible clinical depression had an increased chance of preterm birth: 14 percent delivered before the 37th week of pregnancy, versus 10 percent of other women.
The findings, reported in the American Journal of Obstetrics & Gynecology, do not prove that depression directly leads to preterm birth.
The researchers were able to account for some other factors — like a mother's race and age — and depression was still linked to preterm birth risk.
But there are other variables the study could not weigh, like moms' smoking and drinking habits during pregnancy, and their pre-pregnancy weight. So there could be other explanations.
Still, the findings jibe with past studies that have found a link between prenatal depression and preterm birth, said senior researcher Dr. Richard K. Silver, of the NorthShore University HealthSystem and University of Chicago in Illinois.
And with depression being a form of serious stress for moms, a link to preterm birth is also "biologically plausible," Silver told Reuters Health.
Some studies have found that women who use antidepressants during pregnancy have a higher risk of preterm birth — though that does not prove the medications are to blame.
And Silver said he thinks it's more likely that medication use is serving as a "proxy" for potential effects of depression itself.
The current findings are based on more than 14,000 women who were screened for prenatal depression between 2003 and 2011. Nine percent screened positive, which meant they were at risk of clinical depression and were referred for a full evaluation.
Overall, those women went on to have a higher rate of preterm birth. Silver's team then accounted for certain other factors, including the mom's age, race and history of preterm birth.
Even then, women with depression symptoms were 30 percent more likely than symptom-free women to deliver early.
The findings do not prove cause-and-effect, nor that treating depression will prevent preterm births.
Silver said he's not aware of research suggesting that depression treatment — whether it's medication or talk therapy — improves women's pregnancy outcomes.
"That's to be determined," Silver said.
It's a tricky thing to study, he noted, since researchers cannot ethically conduct a clinical trial where they withhold treatment from some depressed pregnant women while treating others.
So researchers have to rely on studies that, for example, look back at women's medical records and see if those who were treated for depression had different pregnancy outcomes than pregnant women whose depression went untreated. And again, those types of studies leave questions about cause-and-effect.
In the meantime, Silver said pregnant women with depression should be educated on the potential warning signs of preterm labor.
Those include pressure in the pelvis that feels like the baby pushing down; vaginal bleeding; and cramps or contractions that come every 10 minutes or more often.
In some cases, medications can be given to stop early labor or at least delay birth.
As for depression treatment, many women do not want to take medication of any kind during pregnancy, Silver noted.
"Talk therapy" or support groups are also options, he said — though the availability can be limited, and insurance coverage spotty. (Neither Silver nor his colleagues report any financial ties to antidepressant makers, and the study had no industry funding.)
All of the women in the current study were screened for depression as part of a universal screening program. According to the American College of Obstetricians and Gynecologists, depression screening can benefit pregnant women, new moms and their families, and should be "strongly considered" by women and their doctors.
But in practice, doctors vary in whether they screen. Silver said his guess is that fewer than half of pregnant women in the U.S. are screened for depression.