• Scientific Evidence
• Helpful actions - what can you do?

A recent study (Wals M 2003) reported that within a population of offspring with one bipolar parent (140 children, 86 bipolar parents), low birth weight was independently associated with increased risk for the development of both mood and non-mood disorders during adolescence. The correlation remained even after the data was corrected for familial loading (number of first and second degree relatives, other than parent, with affective, psychiatric, or substance abuse disorders) and socio-economic status of the family.

This is one of the only studies to date that has identified low birth weight as a specific risk factor for bipolar disorder. However, a very convincing study (Van Os 2001) involving 1520 pairs of mono- and di-zygotic twins documented low birth weight as an independent, causal risk for child problem behavior by age 10. The authors identified a linear correlation between low birth weight and increasing degree of behavior problems; moreover, they reported that the greater the degree of difference between birth weight of the twin pairs (both identical and fraternal), the greater the difference between child problem behavior scores for the offspring at age 10. Because this difference was seen for both monozygotic (genetically identical) and dizygotic (genetically different, but sharing the same uterine environment) twin pair, the authors concluded that the association between birth weight and behavioral problems was not due to either a shared genetic or a shared environmental factor.

In the study above, "child problem behavior" was not a diagnostic measure; instead, it documented the degree of general behavioral and emotional psychopathology. Therefore, although the data from Van os (2001) appears to give evidence to a relationship between low birth weight and later psychopathology, it does not make a specific link between low birth weight and bipolar disorder. However, the same article cited other studies showing that childhood behavioral characteristics can affect the number of negative life events, and/or stressful events, in adulthood. Subjects with bipolar disorder have been shown to have increased experiences of negatiive or stressful life events.

Helpful Actions:

If you know that psychiatric disorders run in your family, you may want to take extra precautions to maintain a normal weight for your fetus during pregnancy. Factors shown to influence fetal weight include: low maternal weight (affected by maternal nutrition), older age of mother, heavy smoking, multiple births, various types of obstetric complications (including premature membrane rupture, bleeding during early/late pregnancy, and preeclampsia).

Moms-to-be might reduce the risk of having a low birth-weight infant by getting early and quality prenatal care, and making sure to get adequate nutrition during pregnancy (pre-natal vitamins may be helpful). Women over the age of 35 have a higher risk of delivering prematurely, or having an underweight infant at full-term.

The CBS News recently ran a segment entitled What Should Moms-to-Be Eat?, that included key foods for women to include during pregnancy for optimal fetal development and growth. One recent study also suggested that drinking pomegranate juice during pregnancy can help reduce fetal stress from low oxygen and decreased blood flow, both of which can lead to premature births. Another recent study preliminarily suggested that nitrous oxide treatment to low-weight babies can help increase oxygen circulation, which can reduce brain cell damage.

Two large studies out of Britain (2004) and Denmark (2002) both suggest that pregnant women who eat a diet rich in fish, particularly during the later terms, are less likely to have underweight babies or pre-term births.

Authors of the British study, which included 11,500 women and their infants, hypothesized that the Omega-3 fatty acids in fish may improve placental blood flow, thus speeding fetal growth. The results of the study showed that, discounting confounding factors such as age, height, weight, and smoking habits of the mother, intaking a higher-than-average amount of fish (the average of this cohort being about 33g of fish per day, the equivalent of 1/3 of a small can of tuna) can increase birth weight by as much as 70-80 grams.

Are all fish equal? Not for pregnant women, says the FDA and EPA.

Guidelines for Fish Intake During Pregnancy (FDA/EPA recommendations, March 2004)

* 2-3 servings a week, not to exceed 12oz total per week
* Eat a variety fish, avoiding those known to contain high levels of mercury
* Good choices for pregnant women: wild salmon, flounder, canned light tuna, catfish, shrimp, pollock
* Avoid: swordfish, mackerel, shark, tilefish, farm-raised salmon. Limit intake of bottom-feeders and shellfish (such as clams)

Scientific Studies:

• Impact of birth weight and genetic liability on psychopathology in children of bipolar parents. J Am Acad Child Adolesc Psychiatry. 2003 Sep;42(9):1116-21.
• Prenatal life and post-natal psychopathology: evidence for negative gene-birth weight interaction. Psychol Med. 2002 Oct;32(7):1165-74
• A prospective twin study of birth weight discordance and child problem behavior. Biol Psychiatry. 2001 Oct 15;50(8):593-9.