BMJ 1997;314:775 (15 March)

Papers

Population based study of rates of multiple pregnancies in denmark, 1980-94

Tine Westergaard, epidemiologist,a Jan Wohlfahrt, statistician,a Peter Aaby, professor,a Mads Melbye, professor and head a

a Department of Epidemiology Research Danish Epidemiology Science Centre Statens Serum Institut Artillerivej 5 DK-2300 Copenhagen S Denmark

Correspondence and requests for reprints to: Professor Melbye

Objective: To study trends in multiple pregnancies not explained by changes in maternal age and parity patterns.
Design: Trends in population based figures for multiple pregnancies in Denmark studied from complete national records on parity history and vital status.
Population: 497 979 Danish women and 803 019 pregnancies, 1980-94.
Main outcome measures: National rates of multiple pregnancies, infant mortality, and stillbirths controlled for maternal age and parity. Special emphasis on primiparous women >=30 years of age, who are most likely to undergo fertility treatment.
Results: The national incidence of multiple pregnancies increased 1.7-fold during 1980-94, the increase primarily in 1989-94 and almost exclusively in primiparous women aged >=30 years, for whom the adjusted population based twinning rate increased 2.7-fold and the triplet rate 9.1-fold. During 1989-94, the adjusted yearly increase in multiple pregnancies for these women was 19% (95% confidence interval 16% to 21%) and in dizygotic twin pregnancies 25% (21% to 28%). The proportion of multiple births among infant deaths in primiparous women >=30 years increased from 11.5% to 26.9% during the study period. The total infant mortality, however, did not increase for these women because of a simultaneous significant decrease in infant mortality among singletons.
Conclusions: A relatively small group of women has drastically changed the overall national rates of multiple pregnancies. The introduction of new treatments to enhance fertility has probably caused these changes and has also affected the otherwise decreasing trend in infant mortality. Consequently, the resources, both economical and otherwise, associated with these treatments go well beyond those invested in specific fertility enhancing treatments.

Key messages

  • National rates of multiple pregnancies have risen from 1.0% to 1.7% during 1980-94 in Denmark; this rise was most pronounced in recent years

  • Multiple pregnancy rates changed particularly among primiparous women >=30 years of age, where the adjusted twinning rate increased threefold and triplet rate ninefold during 1989-94

  • The dramatic increase in the twinning rate seems to be restricted to dizygotic twin pregnancies

  • These changes are believed to be associated with the increasing use of treatments to enhance fertility


Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to StumbleUpon StumbleUpon   Add to Technorati Technorati    What's this?

Relevant Article

Comparison of academic performance of twins and singletons in adolescence: follow-up study
Kaare Christensen, Inge Petersen, Axel Skytthe, Anne Maria Herskind, Matt McGue, and Paul Bingley
BMJ 2006 333: 1095. [Abstract] [Full Text] [PDF]

This article has been cited by other articles:

  • Zhu, J. L., Basso, O., Obel, C., Christensen, K., Olsen, J. (2007). Infertility, infertility treatment and twinning: the Danish National Birth Cohort. Hum Reprod 22: 1086-1090 [Abstract] [Full text]  
  • Christensen, K., Petersen, I., Skytthe, A., Herskind, A. M., McGue, M., Bingley, P. (2006). Comparison of academic performance of twins and singletons in adolescence: follow-up study. BMJ 333: 1095-1095 [Abstract] [Full text]  
  • Beemsterboer, S.N., Homburg, R., Gorter, N.A., Schats, R., Hompes, P.G.A., Lambalk, C.B. (2006). The paradox of declining fertility but increasing twinning rates with advancing maternal age. Hum Reprod 21: 1531-1532 [Abstract] [Full text]  
  • Pinborg, A. (2005). IVF/ICSI twin pregnancies: risks and prevention. Hum Reprod Update 11: 575-593 [Abstract] [Full text]  
  • Basso, O., Christensen, K., Olsen, J. (2004). Fecundity and twinning. A study within the Danish National Birth Cohort. Hum Reprod 19: 2222-2226 [Abstract] [Full text]  
  • Obi-Osius, N, Misselwitz, B, Karmaus, W, Witten, J (2004). Twin frequency and industrial pollution in different regions of Hesse, Germany. Occup. Environ. Med. 61: 482-487 [Abstract] [Full text]  
  • Pinborg, A., Loft, A., Schmidt, L., Andersen, A. N. (2003). Attitudes of IVF/ICSI-twin mothers towards twins and single embryo transfer. Hum Reprod 18: 621-627 [Abstract] [Full text]  
  • Wohlfahrt, J., Andersen, P. K., Mouridsen, H. T., Melbye, M. (2001). Risk of Late-stage Breast Cancer after a Childbirth. Am J Epidemiol 153: 1079-1084 [Abstract] [Full text]  
  • Cheung, Y. B., Yip, P., Karlberg, J. (2000). Mortality of Twins and Singletons by Gestational Age: A Varying-Coefficient Approach. Am J Epidemiol 152: 1107-1116 [Abstract] [Full text]  
  • Andersen, A.-M. N., Wohlfahrt, J., Christens, P., Olsen, J., Melbye, M. (2000). Maternal age and fetal loss: population based register linkage study. BMJ 320: 1708-1712 [Abstract] [Full text]  
  • Jacobsen, R., Moller, H., Mouritsen, A. (1999). Natural variation in the human sex ratio. Hum Reprod 14: 3120-3125 [Abstract] [Full text]  
Access jobs at BMJ Careers
Whats new online at Student BMJ