Talk:Abnormal Development - Twinning

Mortality risk among preterm babies: immaturity versus underlying pathology.

Epidemiology. 2010 Jul;21(4):521-7.

Basso O, Wilcox A.

Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA. olga.basso@mcgill.ca Abstract BACKGROUND: Deaths among preterm births are presumably due to both immaturity and the conditions that cause preterm birth. Their relative contributions are unknown.

METHODS: Using US birth certificates (1995-2002), we estimated what portion of preterm neonatal mortality may be attributable to immaturity alone. Twins have elevated mortality, yet they usually have lower mortality than singletons at most preterm weeks. Twinning itself is a cause of early birth. Thus, at any given preterm week, singletons are more likely than twins to have pathologic causes of preterm delivery. If any such cause is associated with a mortality risk higher than that conferred by twinning, it is possible for singletons to have higher mortality than twins at some preterm weeks. Thus, mortality of twins at those weeks comes closer to describing the risk due to immaturity itself. To exclude high-risk babies, we focused on singletons and twins least likely to have suffered fetal growth disruptions (ie, those with "optimal" birth weight). At each gestational week from 24 to 36, we identified (for twins and singletons separately) the 500-gram weight category with the lowest neonatal mortality, and selected the lower of the 2 mortality rates.

RESULTS: Using the above as our best estimates of mortality due to immaturity alone, we calculated that about half the mortality of singleton preterm babies was due to the pathologies that cause early delivery.

CONCLUSIONS: Factors that cause preterm birth apparently contribute a large proportion of preterm mortality. If so, the prevention of preterm mortality requires more than the postponement of delivery.

PMID: 20407380 http://www.ncbi.nlm.nih.gov/pubmed/20407380

Temporal and territorial analysis of multiple deliveries in Spain (1900-2006).

Twin Res Hum Genet. 2010 Apr;13(2):207-16.

Fuster V, Zuluaga P, Román-Busto J, Colantonio SE.

Department of Zoology and Physical Anthropology, Faculty of Biology, Complutense University of Madrid and GEPS, Spain. vfuster@bio.ucm.es

Abstract Temporal variations in the frequency of multiple maternities in many Western European countries have been described. However, within a single country, regional differences are observed. Urban industrialized regions and rural agricultural areas have experienced in recent decades a distinct decline in multiple deliveries, which in cases have been related to maternal age and parity changes. Research on multiple deliveries in Spain is scarce and none of the studies go back to the beginning of the 20th century or consider regional variation over an extended period of time. The present paper is a yearly study on multiple deliveries in Spain since 1900 including a geographical analysis. Rather than dealing with recent changes in multi-parity, this paper is concerned with Spain's long-term national variation (between 1900 and 2006). The changing pattern of double and triple deliveries was analyzed using data from the Spanish National Statistics Institute (INE). Twinning rates in Spain are low in comparison to those of equivalent periods in other countries, and the minimum rates correspond to the 1980s decade. Results were interpreted by taking into account the influence of age at maternity and reproductive variation up to 1990. A good fit between observed and predicted rates was obtained after the application of models, which besides maternal age and parity, include their interaction. Regarding territorial variability, the values corresponding to southern, northern and insular Spanish provinces are consistent with an earlier reduction of the crude birth rate in the north-east regions and latter in the southern regions and the Canary Islands.

PMID: 20397751 http://www.ncbi.nlm.nih.gov/pubmed/20397751