Antidepressants may affect fetus

A University of California, San Diego (UCSD) School of Medicine collaborative study with Boston University's Slone Epidemiology Center found an increased risk of persistent pulmonary hypertension (PPHN) in newborns of mothers who used certain commonly prescribed antidepressants in late pregnancy.

The results of the study are published in the New England Journal of Medicine.

According to the study authors, PPHN is a serious condition that typically involves severe respiratory failure in a newborn infant and requires immediate treatment. The condition occurs in about one to two per thousand babies. The new study findings indicate that pregnant women who take one of the antidepressants known as selective serotonin reuptake inhibitors or SSRIs, such as Prozac., Paxil. or Zoloft., in the second half of pregnancy have a small but significantly increased chance of delivering an infant who develops PPHN. The study found that exposure to antidepressants other than SSRIs did not pose a risk for PPHN. In addition, women who discontinued use of SSRIs in the first half of pregnancy did not have an increased risk of delivering a child with the condition.

These findings may be important for pregnant women and clinicians when making decisions about the most appropriate treatments for depression late in pregnancy.

Lead author on the study, Christina Chambers, Ph.D., M.P.H., of the Departments of Pediatrics and Family and Preventive Medicine at UCSD, worked with a team of investigators who identified at birth 377 infants with PPHN and 836 normal newborns from 97 delivery hospitals in four metropolitan centers in the U.S. and Canada between 1998 and 2003. The study was part of the ongoing Birth Defects Surveillance Program being conducted by the Slone Epidemiology Center with the collaboration of 17 San Diego County hospitals including UCSD Medical Center.

Within six months after birth, the researchers examined the records and carefully interviewed the mothers of children with PPHN and the mothers of the matched control infants selected from the same hospitals. The mothers in both groups were asked specifically about the use of any antidepressant medications during pregnancy, the names of products used, and the timing in gestation when the mother used the medication. Mothers were also queried about a wide variety of other maternal exposures, medical history, pregnancy history, and lifestyle factors.

"Based on our findings, we estimate that six to twelve mothers per thousand who use an SSRI after 20 weeks' gestation, are likely to deliver a child with PPHN," said Chambers. "Put in practical terms, the risk is relatively low -- about 99 percent of women exposed to one of these medications during the latter half of pregnancy will deliver an infant unaffected by PPHN."

"Our findings suggest that prenatal exposure to SSRIs might contribute to the pathological origin of this disorder," says Chambers. She adds that although the study cannot establish cause, several possible mechanisms suggesting an association between the use of the SSRIs and PPHN are plausible.

Although the researchers noted an increased risk of PPHN in infants whose mothers took SSRIs late in pregnancy, the research team points out that mothers may need to continue SSRI treatment during pregnancy in order to care for themselves appropriately. The findings of this study might be factored into decisions about continuing treatment with SSRIs into late pregnancy.