Pregnant women with specific alterations in two genes may be at increased risk of suffering depression after giving birth, a little new study indicates.

The researchers hope they can use the findings to develop a blood test that could help spot pregnant women who are exposed to postpartum depression, which affects around 15 percent of new mothers.

Their study, reported in the May 21 issue of the journal Molecular Psychiatry, uncovered particular chemical changes in two genes that predicted which girls would develop postpartum depression with 85 percent precision.

Little is known regarding the genes, called TTC9B and HP1BP3, however they are somehow involved with action in the hippocampus, which regulates mood of the brain. According to animal research, both genes appear to be “reactive to estrogen,” said Zachary Kaminsky, a researcher at Johns Hopkins University School of Medicine in Baltimore who worked on the study.

The findings offer hints as to what makes some women susceptible to postpartum depression. But there’s still a lot of work before a screening test becomes available, according to an expert not involved with the research to be done.

“This is a first step, but I think we are pretty far off from having a blood test,” said Dr. Kimberly Yonkers, a professor of psychiatry and obstetrics and gynecology at Yale School of Medicine in New Haven, Conn.

She said the study was not large — involving just 51 women, about a dozen of whom acquired depression of giving birth in a month — so the results have to be validated in larger studies.

But beyond that, Yonkers said, there is the larger, “dicey” problem of just how much gain there would be from telling pregnant women their genes put them at heightened risk of postpartum depression.

“You may unnecessarily stress some women,” Yonkers said.

“Information is power,” Kaminsky said, and for some women, understanding they are prone to postpartum depression could offer to be able to minimize that danger: Their partner, family or friends may be particularly careful and step directly into calm some of the stress of being a new mom, by way of example.

Kaminsky recognized that if a blood test result really caused distress for an expectant mom, it could not be great. But, he said, having a blood test as a choice for women who want a concept of the risk could be precious.

Kaminsky and two of his co-researchers have filed for a patent on testing for the genetic markers.

The findings are based on 51 pregnant women using a history of depression or bipolar disorder, which raises the risk of enduring depression during or after pregnancy. One group of 19 women had major depression during their pregnancies, and 12 continued to have symptoms in the first month

Another 32 women were depression-free but 11 developed postpartum depression, during pregnancy.

Based on research with mice, the team of Kaminsky surmised that estrogen activates so called epigenetic changes in genes in the mind ‘s hippocampus. A gene’s action is altered, although with epigenetic changes, there’s no defect in the underlying DNA. The results of research conducted in mice, however, often are unable to be reproduced in people.

The researchers found that epigenetic changes in the HP1BP3 and TTC9B genes were predictive of a woman’s risk of postpartum depression.

Yonkers said one theory has been that women who develop postpartum depression may respond differently to the enormous shifts in estrogen and other hormones that happen during pregnancy and following childbirth.

Kaminsky said the new findings give some insight into that hormonal response. But he said more research is needed to really understand what is going on.

The results additionally should be validated in a larger, more varied group of women, Kaminsky said. “The girls in this study all had been formerly identified as having depression or bipolar disorder,” he said. “We really must look at this in a broad population of women too.”

In general, experts suspect that many factors come together to cause postpartum depression, including a female ‘s specific situation, such as whether she’s a great “support network,” if she has other important stressors in her life or whether the pregnancy was planned or not.

So no blood test would tell the complete narrative.

Right now, physicians may diagnose postpartum depression because a female complains of symptoms, or by way of a screening questionnaire. Yonkers said experts differ on whether new mommies must be routinely screened; the American Academy of Pediatrics, for instance, says pediatricians should screen moms for depression during checkups that were newborn.

Other groups, like the American College of Gynecologists and Obstetricians, do not counsel routine screening, but girls and say doctors should consider it.