Antidepressant use in expecting mothers can cause their babies to develop pulmonary hypertension, a condition that increases blood pressure in the lungs, according to a study published Thursday in the British Medical Journal.

Babies born from mothers who took the most prescribed type of antidepressants, serotonin reuptake inhibitors (SSRI) during pregnancy were twice as likely to develop pulmonary hypertension compared with mothers who did not take the medications.

The study could impact about 1.5 percent of pregnant women in the U.S. - the percentage of expecting mothers who take the antidepressants more commonly known by their brand names of Zoloft, Paxil, and Celexa and Lexapro.

Researchers reviewed records from 6 million births from 1996 to 2007 in Nordic countries and found the risk of pulmonary hypertension doubled in infants whose mothers took SSIs.

Experts said that the risk remained low.

You're doubling the risk of extremely low risk to again, an extremely low risk, Marjorie Greenfield, division director of obstetrics and gynecology at University Hospitals Case Medical Center in Cleveland, told ABC News.

The U.S. Food and Drug Administration agreed with the low risk conclusion in December by advising physicians to continue treating expectant mothers with antidepressants.

Given the conflicting results from different studies, it is premature to reach any conclusion about a possible link between SSRI use in pregnancy and PPHN [pulmonary hypertension], the FDA announced in December.

This is by far the largest study to examine SSRI use and PPHN, but the fact that women with untreated depression had a higher risk for the disorder raises new doubts about this link, Gideon Koren of Toronto's Hospital for Sick Children, told WebMD. Many doubts remain, and they should be shared with patients.

Even with that doubt, previous studies have found other risk factors that can cause infants to have hypertension, which reduces the blood flowing in the developing lungs of newborns that decreases oxygen levels and in extreme cases can cause death.

According to a 2007 study from researchers at Boston University, expecting mothers have other risk factors linked to newborn hypertension, factors that pregnant women could help reduce to help their infant, though the clinical relevancy of this hasn't been tested:

1. Lose Weight

Mothers who are either overweight and/ or resistant to insulin do not allow their fetus to develop lungs properly because the mothers induce inflammation while the delicate tissue matures. Losing weight might also help manage diabetes, another risk factor in hypertension, scientists have found.

2. Quit Smoking

Researchers know that expecting mothers who smoke damage their developing fetus and this holds true with hypertension, too. Smoking impairs the placenta which shuttles oxygen and nutrients to the fetus and keeps poisons at bay. Smoking in mothers decreases the amount of oxygen a mother gives to her developing fetus, a condition known as hypoxemia.

3. Favor Natural Child Birth

Numerous groups have found that cesarean section delivery of an infant is linked with higher incidences of a condition known as respiratory distress syndrome, which is also linked to hypertension. One reason given by experts is that doctors may miscalculate the gestation time and deliver a baby before it is fully developed prenatally. Another theory is that a baby delivered by cesarean might not become flooded wtih prostaglandin and catecholamine hormones that typically help in clearing the lungs of fluid. Cesarean delivery increases the risk of hypertension to one in 100 births. Typically, hypertension affects one to two in 1,000 births.

4. Be Aware of Racial Factors

While you can't change your race, it is important for expecting mothers to be aware of risks for their infant. Many studies have found that black and Asian infants have higher incidences of hypertension compared with white infants, regardless of socioeconomic factors such as education levels and income. Scientists still do not understand what may be underlying these differences.