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Preterm birth tied to lifelong problems

March 25, 2008
Courtesy Duke University
and World Science staff

Prem­a­ture birth leads to health prob­lems much more var­ied and long-last­ing than pre­vi­ously real­ized, ac­cord­ing to a study of more than a mil­lion adults.

Re­search­ers at the Duke Med­i­cal Cen­ter in North Car­o­li­na say pre­term birth con­tri­butes to sev­er­al long-term health is­sues in­clud­ing low­er educa­t­ional achieve­ment, low­er rates of re­pro­duc­tion, and an in­crease in the like­li­hood that fu­ture off­spring will be born preterm and with com­plica­t­ions.

Prem­a­ture birth leads to health prob­lems that are more var­ied and last much long­er in­to adult­hood than pre­vi­ously real­ized, ac­cord­ing to a long-term study of more than a mil­lion adults. (Image cour­tesy Nat'l Inst. of Health)
The find­ings ap­pear in the March 26 is­sue of the Jour­nal of the Amer­i­can Med­i­cal As­socia­t­ion.

Preterm birth, mean­ing birth be­fore 37 weeks of gesta­t­ion, is the lead­ing cause of in­fant mor­tal­ity. “When a ba­by is born preterm, we tend to fo­cus on the short-term risk of com­plica­t­ions,” said Geeta Swa­my, a maternal-fe­tal med­i­cine spe­cial­ist at Duke, and lead au­thor of the stu­dy.

“While it is true that the risk of com­plica­t­ions is high­est in the im­me­di­ate time per­i­od in­clud­ing hos­pi­tal­iz­a­tion and the first year of life, that risk con­tin­ues in­to ad­o­les­cence. And the ear­li­er you’re born, the high­er the risk. Those who are born ex­tremely prem­a­turely are more likely to have com­plica­t­ions through­out their lives.”

Work­ing with col­leagues at the Nor­we­gian In­sti­tute of Pub­lic Health, Swa­my and fel­low re­search­ers used a na­tional popula­t­ion-based reg­is­try con­tain­ing birth and death da­ta to an­a­lyze how preterm birth af­fects long term sur­viv­al, sub­se­quent re­pro­duc­tion and next-genera­t­ion preterm birth. The popula­t­ion stud­ied spanned 20 years, from 1967 through 1988. Births oc­curred on or af­ter 22 weeks and through 37 weeks gesta­t­ion. 

The study found:
  • Boys born be­tween 22 and 27 weeks had the high­est rate of early child­hood death.

  • Re­pro­duc­tion rates were con­sid­erably low­er for men and wom­en born preterm when com­pared to those born at term. Re­pro­duc­tion in­creased in di­rect pro­por­tion to high­er gesta­t­ional age. 

  • Wom­en born preterm were more likely to ex­pe­ri­ence re­cur­rent preterm birth and an in­creased risk of ad­verse out­comes in their off­spring. A si­m­i­lar pat­tern was re­ported for fe­tal still­birth and in­fant mor­tal­ity among wom­en born preterm.

  • The low­er the gesta­t­ional age, the great­er the risk of hav­ing less educa­t­ion.

Gesta­t­ional age plays a very large role in over­all health, Swa­my said. Low birth weight has been the tra­di­tion­al in­di­ca­tor of how well a ba­by will do. How­ev­er, Swa­my now be­lieves gesta­t­ional age may be an even stronger pre­dic­tor. 

In ad­di­tion, she said the re­search raises an im­por­tant ques­tion con­cern­ing the long-term ef­fects of ad­vanc­es in pre­na­tal and ne­o­na­tal care. “Preterm sur­viv­al is im­prov­ing now be­cause of in­ter­ven­tions we have in preg­nan­cy and ne­o­na­tal care. How­ev­er, it may be that we’re im­prov­ing sur­viv­al while ad­versely af­fect­ing the over­all health and qual­ity of life in the long run.”

* * *

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Premature birth leads to health problems that are more varied and last much longer into adulthood than previously realized, according to a long-term study of more than a million adults. Researchers at the Duke Medical Center in North Carolina say preterm birth contributes to several long-term health issues including lower educational achievement, lower rates of reproduction, and an increase in the likelihood that future offspring will be born preterm and with complications. The findings appear in the March 26 issue of Journal of the American Medical Association. Preterm birth, meaning birth before 37 weeks of gestation, is the leading cause of infant mortality. “When a baby is born preterm, we tend to focus on the short-term risk of complications,” said Geeta Swamy, a maternal-fetal medicine specialist at Duke, and lead author of the study. “While it is true that the risk of complications is highest in the immediate time period including hospitalization and the first year of life, that risk continues into adolescence. And the earlier you’re born, the higher the risk. Those who are born extremely prematurely are more likely to have complications throughout their lives.” Working with colleagues at the Norwegian Institute of Public Health, Swamy and fellow researchers at Duke used a national population-based registry containing birth and death data to analyze how preterm birth affects long term survival, subsequent reproduction and next-generation preterm birth. The population studied spanned 20 years, from 1967 through 1988. Births occurred on or after 22 weeks and through 37 weeks gestation. The study found: Boys born between 22 and 27 weeks had the highest rate of early childhood death. Reproduction rates were considerably lower for men and women born preterm when compared to those born at term. Reproduction increased in direct proportion to higher gestational age. Women born preterm were more likely to experience recurrent preterm birth and an increased risk of adverse outcomes in their offspring. A similar pattern was reported for fetal stillbirth and infant mortality among women born preterm. The lower the gestational age, the greater the risk of having less education. Gestational age plays a very large role in overall health, Swamy said. Low birth weight has been the traditional indicator of how well a baby will do. However, Swamy now believes gestational age may be an even stronger predictor. In addition, she said the research raises an important question concerning the long-term effects of advances in prenatal and neonatal care. “Preterm survival is improving now because of interventions we have in pregnancy and neonatal care. However, it may be that we’re improving survival while adversely affecting the overall health and quality of life in the long run.”