Due dates help expectant mothers establish a development timeline to keep track of their fetuses’ progression. However, length of pregnancy can still vary by about five weeks, which means birth and delivery aren't always predictable. The expected labor date can be a predictor of infant health, especially when it comes to their brains.

A new study published in the International Journal of Epidemiology suggests being born either too early or too late could influence a baby's academic performance later in life.

Premature infants face a high risk of cognitive and development problems. Previous research has found full-term babies experience more brain growth during the third trimester (final 13 to 14 weeks of pregnancy) compared to premature infants, who are born before 37 weeks. During the third trimester, fetuses' brains grow exponentially, and the body shifts energy to the brain to make room for a neurological growth spurt. The brain increases four times in size, and develops critical structures and connections that will be relied upon for life.

Unlike full-term infants, preemies’ brains possess lower volumes in the cerebrum (largest part of the brain controlling speech, thoughts, emotions, learning, and muscle function); cerebellum (helps with learning and social-behavioral functions and complex motor skills), controlling the balance to stand up and to walk; and the brain stem (acts as a router, facilitating communication between the brain, the cerebellum, and the spinal cord).

With this in mind, Swedish researchers sought to examine the relationship between gestational age at birth and academic performance at age 16 by analyzing data of over 2 million live births with a pregnancy duration of 22 to 45 completed weeks between 1973 and 1994. Academic performance was measured by the final grade achieved on completing secondary education at 16.

Between 1973 and 1994, about 9 percent of Swedish births were post-term and 4.6 percent were preterm. Late preterm children (3.6 percent) were more likely to have been exposed to maternal medical risk or birth complications.

The findings revealed grades were lower for preterm and post-term babies than their control group counterparts, especially in those who showed poor fetal growth (i.e., poor nutrition during pregnancy), despite gestational age. Grades for extremely preterm births (24 weeks) were lower by 0.43 standard deviations, while grades for extremely post-term births (45 weeks) were only lowered by 0.15 deviations. In other words, being born extremely early has more cognitive consequences than being born extremely late. However, induced post-term deliveries were not linked with reduced school performance.

"Less favorable outcomes of post-term infants with poor fetal growth suggest that placental insufficiency may become particularly toxic to neurodevelopment the longer a pregnancy endures," said lead author Dr Hein Heuvelman, in a statement.

These findings suggest poor development is likely when babies are born earlier, especially if it’s an induced birth. Typically, planned births might include labor inductions or surgical cesarean section deliveries. Labor induction is vital in certain situations, like preeclampsia, when continuing the pregnancy is more of a risk to the mother or baby. Unless there’s a genuine medical reason, expectant mothers should wait to go into labor naturally to maximize their child’s chances of better brain development.

Source: Abel K, Heuvelman H, Wicks S et al. Gestational age at birth and academic performance: population-based cohort study. International Journal of Epidemiology. 2016.