We already know there are long-term health problems associated withpre-term birth, but what about babies born post-term? New researchpublished in the International Journal of Epidemiology has found that post-term birth, defined as a birth after apregnancy of 42 weeks, is associated with more behavioural andemotional problems in early childhood, especially AttentionDeficit/Hyperactivity Disorder ( ADHD ) problems. Lead author Hanan El Marroun, of the study entitled 'Post-termbirth and the risk of behavioural and emotional problems in earlychildhood', comments that "post-term children have a considerablyhigher risk of clinically relevant problem behaviour and are morethan twice as likely as term born children to have clinical ADHD.Further research is needed in order to determine the causes ofpost-term birth and to minimize the long-term consequences. It isalso important that further research is carried out in order todemonstrate a causal relation between post-term birth andbehavioural problems and longer follow ups would also beadvantageous." The research found a U-shaped association between gestational ageat birth and behavioural and emotional problems in early childhood.This indicates that both preterm and post-term children are athigher risk for problems. Post-term children were almost twice aslikely as term born children to have behavioural and emotionalproblems and were more likely to show problems in the clinicalrange on the ADHD scale. |
A linear regression analysis also showed acurvilinear relation between gestational age and behaviouralproblems for the continuous scores on the total problems, ADHD,affective problems scale and pervasive developmental problems,which suggests that children with a shorter or longer gestationhave a higher behavioural problem score compared to children bornat term. The study was embedded in the Generation R Study, a largepopulation-based prospective cohort study from foetal life onwards.Pregnant mothers who were residents of Rotterdam and due to givebirth between April 2002 and January 2006 were asked to participateby their midwives and gynaecologists. The researchers measuredgestational age using ultrasound, a method thought to be superiorto date of last period. Based on this measure, out of a total of5145 babies, 382 (7%) were born post-term and 226 (4%) were bornpre-term. A standardized and validated behavioural checklist (ChildBehaviour Checklist, CBCL/1.5-5) was used to assess the children.At both 18 and 36 months old a postal questionnaire was sent to themother of the child and the father was also sent a questionnairewhen the child was aged 36 months.
Both post-term and pre-termbabies were at higher risk of behavioural and emotional problems at18 and 36 months. Supplementary analysis found similar results when children whosegestational age was measured in the second or third trimester wereexcluded and the results did not appear to be explained by factorssuch as mother's weight and height, ethnicity, family income,alcohol consumption, smoking, education level or maternalpsychopathology in mid-pregnancy. However, the authors point outthat although they controlled for a large number of covariates,other factors, for example maternal malnutrition during pregnancy, cannot be ruled out. The authors propose several potential explanations for theirfindings.
First they discuss the higher risk of perinatal problemsknown to be associated with larger babies. However, excludingbabies that weighed over 4000 grams at birth and babies that wereinduced did not alter their findings. Second they discussuteroplacental insufficiency; the situation in which an "old"placenta offers fewer nutrients and less oxygen than required by afull term foetus. This lack of nutrients and oxygen may predisposeto abnormal foetal development which, in turn, may lead to abnormalemotional and behavioural development. However, the observationalnature of the present study did not enable the authors todistinguish possible effects of uteroplacental insufficiency fromperinatal problems.
Third they discuss potential disturbance of the"placental clock" which controls the length of pregnancy andregulates the maternal and foetal hypothalamic-pituitary-adrenalaxis (HPA-axis). It has been suggested that placental endocrinemalfunctioning or maternal stress at critical times during foetal development may influence thefoetal HPA-axis, leading to neuroendocrine abnormalities that couldincrease the child's vulnerability to emotional and behaviouralproblems later in life. Finally, they suggest that the same causemay underlie being born post-term and having behavioural problems,for example, neurodevelopmental factors related to behaviouralproblems could be involved in the complex process of birth. The authors caution that longer follow-up is necessary to establishwhether the relationship between post-term birth and behaviouralproblems persist beyond 36 months. However, they also advise thatpractitioners involved in the management of prolonged pregnancyshould take note of their findings.
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