Born Small for Gestational Age : Beyond Size at Birth

Sammanfattning: Children born small for gestational age (SGA) run increased risk of perinatal morbidity and mortality, but also of long-term health impairment. Risks on long term may vary depending on postnatal growth patterns. The overall aim of the thesis was to gain further knowledge about long-term consequences of being born SGA, as well as the impact of perinatal exposures on postnatal growth patterns. The thesis is based on four register-based cohort studies.In paper I, risk of chronic hypertension was assessed in 731,008 first-time mothers. Perinatal exposure to pre-eclampsia, being born SGA and preterm were all independently associated with increased risk of chronic hypertension. The risk was further enhanced after combined exposure. The strongest association was seen in combinations including pre-eclampsia.In paper II, risk of poor school performance at time of graduation from compulsory school was assessed in 1,088,980 children born SGA at term. Being born SGA was associated with increased risk of poor school performance, following a dose-response pattern with increased risk even for birthweight for gestational age (GA) –1.01 to –2 SD. Boys with short adult stature were associated with higher risk of poor school performance than those with non-short stature.In paper III, differences in postnatal growth patterns depending on SGA status and maternal smoking habits were assessed in 32,493 children. Children born SGA with smoking mothers had a more rapid catch-up growth than those with non-smoking mothers. Compared with children born appropriate for GA (AGA) with non-smoking mothers, only children born SGA with non-smoking mothers were associated with increased risk of short stature at 1.5 and 5 years.In paper IV, differences in postnatal growth patterns until age five years, depending on SGA status and GA at birth, were assessed in 41,669 children born between 32-40 gestational weeks. Being born SGA and moderate to late preterm was associated with shorter stature and lower BMI, compared with being born AGA at term. SGA status had greater impact on growth and body proportions than GA at birth.In conclusion, children born SGA are at higher risk of chronic hypertension and cognitive impairment than children born AGA. Postnatal growth patterns vary in children born SGA, depending on intrauterine exposure to smoking and GA at birth. This may modify risks of long-term health impairment.