Study shows Baby Temperament affected by Maternal Sensitivity

A recent study published reveals that a child's temperament may be influenced by maternal postpartum depression, maternal sensitivity, and family functioning. Maternal depression was associated with difficult temperaments in infants when maternal sensitivity was low, but not when maternal sensitivity was high. Family functioning similarly moderated these links.

The findings suggest that family factors play a critical role in shaping the trajectory of an infant's behavioral style as it unfolds over development.

For example, even when dealing with depression, mothers who consistently and appropriately respond to their infants' needs, which are hallmarks of sensitive parenting, may more effectively teach their infants how to regulate their negative emotions than mothers who respond less sensitively. Similarly, a highly functioning family unit characterized by effective communication and high interpersonal involvement among family members may support an infant's emotion regulation even when the mother is depressed.

“Maternal postpartum depression was only associated with persistently difficult infant temperament when other family risk factors were present," said Dr. Stephanie Parade, lead author of the Child Development study. "This work underscores the importance of supporting families in the postpartum period."

During pregnancy

In a Johns Hopkins University study, researcher Janet DiPietro concluded, “the human brain requires sufficient, but not overwhelming, stress to promote optimal neural development both before and after birth.”

Pietro and colleagues studied pregnant women who were mentally healthy, well-educated, and had low-risk pregnancies. Midway through the pregnancies, Pietro measured the level of the mothers’ psychological distress (stress, anxiety, or depression). After the babies were born, she tested their development at six weeks and then again at the two-year point. She found that babies whose mothers had mild-to-moderate distress were more advanced in their physical and mental development. Another study showed that the babies’ brain development benefited from a little prenatal stress, maturing a bit faster, with quicker connectivity among neurons.

Does that mean that women should welcome stress in order to boost their fetus’ development?

Absolutely not. According to DiPietro, the normal stresses of modern life are enough already. “The last thing a new mom needs is to head into newborn baby care stressed and exhausted.” In other words, healthy women leading reasonably normal lives can “stop worrying about worrying.”

Stress Factors

On the other hand, when women experience severe stress during pregnancy, their babies can be at risk for serious problems. What kinds of stresses are harmful?

In studies on pregnant women, significant stress can mean any event, ranging from loss of a loved one to violence, natural disasters like a flood, and the end of a relationship. These stresses have been linked to subsequent miscarriage or low birth weight in infants. Stress that is chronic—like poverty, homelessness, racism, and discrimination—can also lead to low birth weight, as well as later physical and psychological problems.

Newborn babies of mothers who were depressed during pregnancy are four times more likely to have a low birth weight than babies born to mothers who are not depressed. When women are depressed during pregnancy, there’s also a greater likelihood that they’ll suffer postpartum depression, which can become a major challenge for the whole family. Not only does the mother suffer, but research shows that depression in the primary caregiver is one of the strongest predictors of poor developmental outcomes in children. These children simply do not receive the normal interpersonal feedback they need in order to grow in emotionally healthy ways.

Fetal temperament

Psychologists have long known that babies enter the world with different temperaments. For example, some babies seem easy and sociable while others are more reactive, difficult to soothe, and are more sensitive to their environment. Until recently, scientists thought babies were “just born that way,” with temperaments that were part of their makeup, or “inherited” from parents.

But the new research on fetal development changes that theory, with a more complete understanding of the interplay between biology and environmental influences—even before birth.

Catherine Monk, Professor of Medical Psychology in Psychiatry and Obstetrics and Gynecology at Columbia University Irving Medical Center, and her colleagues study the long reach of prenatal influences, especially among women who suffer from depression, stress, and anxiety. They found that some fetuses register mothers’ stress, and that fetal reactivity correlates with infant temperament at four months.

Monk and her colleagues brought 50 pregnant women into the lab and monitored the fetal heart rate while the women completed the Stroop Test, a mildly stressful mental task. Fetuses of women who were clinically depressed or anxious showed they registered the performance stress of their mothers, by the changes in their heart rates during the task. Later, when the babies were four months old, researchers assessed their temperaments by watching how reactive they were to a range of new stimuli (sounds, sights, smells), and some important patterns emerged. In particular, fetuses who had greater heart rate changes during their mothers’ task were more likely to be highly reactive at four months of age.

Follow-up have shown while the heart’s reaction to stress is important and how quickly the heart returns to baseline—is also predictive. A quicker heart-rate recovery in the fetal period predicts an easier temperament and even more prosocial behavior later in childhood.

But a baby isn’t born with a thermostat set to some pre-determined level. Instead, a fetus is programmed to listen for cues about their future environment and adaptation begins in the womb.

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