PITTSBURGH — Women with a history of bipolar disorder have an increased risk of developing depression during and after pregnancy, based on a review of more than 2,000 pregnant women.
A history of unipolar depression also predisposed women to develop depression during the peripartum and postpartum periods, although unipolar depression was not as potent a risk factor as bipolar disorder. The findings suggest “an urgent need” for better screening and detection of bipolar-spectrum disorders in pregnant women, Adele C. Viguera, M.D., said while presenting a poster at the Sixth International Conference on Bipolar Disorders.
The results show that pregnant women with a history of bipolar disorder or unipolar depression are “ticking time bombs” for the development of peripartum or postpartum depression, Dr. Viguera, associate director of perinatal and reproductive psychiatry at Massachusetts General Hospital, Boston, told this newspaper.
Women with bipolar disorder who are treated with lithium while breast-feeding transfer a modest amount of lithium to their infant children. “Adverse clinical effects in infants exposed to lithium through breast milk were rare and clinically insignificant” in a study with 10 mother-infant pairs, Dr. Viguera reported in a second poster at the conference, which was sponsored by the University of Pittsburgh.
The prevalence of bipolar depression in pregnant women and its association with peripartum and postpartum depression was assessed in 2,340 consecutive women who sought prenatal care at the Massachusetts General Hospital during 1996–1999.
A mood-disorder questionnaire was completed by 1,814 of the study participants during their second trimester, and 526 women completed a second questionnaire when they were seen at the clinic 6 weeks after delivery.
Bipolar disorder was diagnosed in women with a self-reported history of mania with or without a history of depression. Depression during pregnancy or the postpartum period was diagnosed when women scored at least 16 on the Center for Epidemiologic Studies Depression Scale.
The average age of the entire group of 2,340 women was 32.5 years, and 61% did not have children before the index pregnancy.
The women who finished their pregnancy questionnaires had a 3.2% overall prevalence of probable bipolar disorder at some time during their lives.
In the second trimester, the prevalence of depression was about 52% among women with a history of bipolar disorder, about 34% among those with a history of unipolar depression, and about 8% among women with no history of a mood disorder. The differences between the bipolar and unipolar groups and the women with no mood disorders were statistically significant, Dr. Viguera reported.
At the sixth week post partum, the prevalence of depression was 50% among women with a history of bipolar disorder, about 32% among women with a history of unipolar depression, and about 6% among women with no history of mood disorders. Again, the prevalence of depression was significantly greater among women with a history of bipolar disorder or unipolar depression, compared with those who did not have this history.
During and after pregnancy, depression should be closely monitored, especially in women with a history of depression or bipolar disorder. These women can be treated like any other patients with these disorders, Dr. Viguera said. Patients with bipolar disorder should receive a mood stabilizer, while those with unipolar depression should get an antidepressant.
The passage of lithium from mother to child via breast milk was examined in a separate study that involved 10 mother-infant pairs. Serum and breast milk samples were obtained from both the mothers and infants at 4–12 weeks' post partum, both before a dose of lithium was administered and within 12 hours after a dose. Repeat samples were collected from five subjects.
The average maternal dose of lithium was 850 mg/day, which led to an average serum concentration of 0.76 mEq/L. The average lithium concentration in milk was 0.35 mEq/L, and the average serum level in the infants was 0.16 mEq/L.
The findings suggest a “rule of halves” for lithium: Breast milk contains about half the lithium concentration as maternal serum, and infant serum contains about half of the concentration in breast milk, Dr. Viguera said. (This means that infant serum contains about one-fourth the concentration in maternal serum.)
Nine of the 10 infants in the study showed no adverse effects from lithium exposure. One infant had an elevated level of TSH, but the level normalized within 2 weeks after lithium was stopped. All of the other nine infants had TSH levels that were within the normal range. Renal function was normal for all 10 infants, and there were no other acute effects seen. Follow-up observations and reports also showed no late developmental abnormalities.