Mortality of twins and singletons by gestational age: a varying-coefficient approach.

This study used data from the Swedish Medical Birth Registry between 1982 and 1995 to address the question of whether there is higher mortality in twins in relation to singletons of the same gestational age and to examine the optimal gestational age range for twins. A "varying-coefficient approach" was adopted to estimate the gestational age-specific relative and absolute risks of mortality in twins and singletons, adjusting for size at birth and risk factors of short gestational duration. The models showed that twins born between 29 and 37 weeks of gestation had lower mortality than did singletons of the same gestational age. Twins born at older gestational age had higher mortality than did their singleton counterparts, because longer gestational duration was more advantageous to singletons than to twins. Without adjustment for size at birth, there was an upturn of mortality in twins born after 38 weeks. It is postulated that twins have better health than singletons initially, but they could not enjoy the benefit of a longer gestational duration as much as singletons could. The optimal gestational age for twins appeared to be 37-39 weeks according to neonatal and infant mortality.

[1]  D. Caine.  The Cambridge Encyclopedia of human growth and development , 2000 .

[2]  S. Cnattingius,et al.  Preterm birth and maternal smoking: risks related to gestational age and onset of delivery. , 1998, American journal of obstetrics and gynecology.

[3]  A. Figueiras,et al.  Regression models: calculating the confidence interval of effects in the presence of interactions. , 1998, Statistics in medicine.

[4]  R. Platt,et al.  How small is too small in a twin pregnancy? , 1998, American journal of obstetrics and gynecology.

[5]  U. Hogberg,et al.  Early dating by ultrasound and perinatal outcome. A cohort study. , 1998, Acta obstetricia et gynecologica Scandinavica.

[6]  J. Martin,et al.  What are the fetal growth patterns of singletons, twins, and triplets in the United States? , 1998, Clinical obstetrics and gynecology.

[7]  F. Malone,et al.  Neonatal Morbidity and Mortality Associated With Triplet Pregnancy , 1998, Obstetrics and gynecology.

[8]  J. Kiely,et al.  What is the population-based risk of preterm birth among twins and other multiples? , 1998, Clinical obstetrics and gynecology.

[9]  J. Olsen,et al.  Low birth weight and preterm birth after short interpregnancy intervals. , 1998, American journal of obstetrics and gynecology.

[10]  H. Oosting,et al.  Term and postterm twin gestations. Placental cause of perinatal mortality. , 1997, The Journal of reproductive medicine.

[11]  U. Hogberg,et al.  Early dating by ultrasound and perinatal outcome , 1997 .

[12]  S. Craigo,et al.  A comparison of neonatal outcomes of age-matched, growth-restricted twins and growth-restricted singletons. , 1997, American journal of perinatology.

[13]  M. Segal,et al.  Maternal smoking during pregnancy and birth outcomes with weight gain adjustments via varying-coefficient models. , 1997, Statistics in medicine.

[14]  Kramer Ms.  Preventing preterm birth: are we making any progress? , 1997 .

[15]  M. Melbye,et al.  Population based study of rates of multiple pregnancies in denmark, 1980-94 , 1997, BMJ.

[16]  H. Minakami,et al.  Date of Delivery in Multifetal Pregnancies-Reply , 1996 .

[17]  R. Goldenberg,et al.  The Origin and Outcome of Preterm Twin Pregnancies , 1995, Obstetrics and gynecology.

[18]  J. Kiely,et al.  The risks confronting twins: a national perspective. , 1994, American journal of obstetrics and gynecology.

[19]  B. Luke,et al.  The ideal twin pregnancy: patterns of weight gain, discordancy, and length of gestation. , 1993, American journal of obstetrics and gynecology.

[20]  R. Tibshirani,et al.  Varying‐Coefficient Models , 1993 .

[21]  B. Luke,et al.  The Role of Fetal Growth Restriction and Gestational Age on Length of Hospital Stay in Twin Infants , 1993, Obstetrics and gynecology.

[22]  P. Buekens,et al.  Why do small twins have a lower mortality rate than small singletons? , 1993, American journal of obstetrics and gynecology.

[23]  H. Rydhström.  A birthweight‐for‐gestation standard based on 4737 twins born in Sweden between 1983 and 1985 , 1992, Acta obstetricia et gynecologica Scandinavica.

[24]  J. Rodis,et al.  A Comparison of Pre‐Discharge Survival and Morbidity in Singleton and Twin Very Low Birth Weight Infants , 1992, Obstetrics and gynecology.

[25]  D. Hosmer,et al.  Applied Logistic Regression , 1991 .

[26]  J. Fryer,et al.  An Update of the Swedish Reference Standards for Weight, Length and Head Circumference at Birth for Given Gestational Age (1977‐1981) , 1991, Acta paediatrica Scandinavica.

[27]  J. Kiely.  The Epidemiology of Perinatal Mortality in Multiple Births , 1990, Bulletin of the New York Academy of Medicine.

[28]  B. Källén,et al.  A Quality Study of a Medical Birth Registry , 1990, Scandinavian journal of social medicine.

[29]  D. Guilkey,et al.  People are not passive acceptors of threats to health: endogeneity and its consequences. , 1990, International journal of epidemiology.

[30]  M. Kramer.  Intrauterine growth and gestational duration determinants. , 1987, Pediatrics.

[31]  K. Leveno,et al.  Fetal lung maturation in twin gestation. , 1984, American journal of obstetrics and gynecology.

[32]  A. Ericson,et al.  Pregnancy Outcome and Social Indicators in Sweden , 1984, Acta paediatrica Scandinavica.

[33]  R. Creasy,et al.  Fetal Growth and Perinatal Viability in California , 1982, Obstetrics and gynecology.

[34]  K. Benirschke,et al.  Multiple pregnancy. 1. , 1973, The New England journal of medicine.

[35]  Tx Station.  Stata Statistical Software: Release 7. , 2001 .

[36]  F. Johnston,et al.  The Cambridge encyclopedia of human growth and development , 1998 .

[37]  S. Kilpatrick,et al.  Perinatal mortality in twins and singletons matched for gestational age at delivery at > or = 30 weeks. , 1996, American journal of obstetrics and gynecology.

[38]  F. Parazzini,et al.  The epidemiology of multiple pregnancies. , 1994, Acta geneticae medicae et gemellologiae.

[39]  David W. Hosmer,et al.  Best subsets logistic regression , 1989 .

[40]  J. Schenker,et al.  Advanced ultrasonic placental maturation in twin pregnancies. , 1987, American journal of obstetrics and gynecology.

[41]  S. Campbell.  Fetal growth. , 1974, Clinics in obstetrics and gynaecology.