Women Born Preterm or with Inappropriate Weight for Gestational Age Are at Risk of Subsequent Gestational Diabetes and Pre-Eclampsia

Introduction: Low birthweight, which can be caused by inappropriate intrauterine growth or prematurity, is associated with development of gestational diabetes mellitus (GDM) as well as pre-eclampsia later in life, but the relative effects of prematurity and inappropriate intrauterine growth remain uncertain. Methods: Through nation-wide registries we identified all Danish mothers in the years 1989–2007. Two separate cohorts consisting mothers born 1974–1977 (n = 84219) and 1978–1981 (n = 32376) were studied, due to different methods o

Defining Smallness for Gestational Age in the Early Years of the Danish Medical Birth Registry

Background: Being born small for gestational age (SGA) is associated with decreased insulin sensitivity and increased blood pressure in childhood, but the association with clinical disease in early adulthood is less certain. The Danish Medical Birth Registry has registered all births in Denmark since 1973, but due to variable data quality, data is most often used only from 1981 onwards, and birth registers in other countries may have similar problems for the early years. We wanted to examine whether the data can be used for identification of children born SGA and used in future research. Methodology/Principal Findings: All persons born between 1974 and 1996 were identified in the Danish Medical Birth Registry (n = 1.704.890). Immigrants and children without data on gestational age and birth weight were excluded, and a total of 1.348.106 children were included in the analysis. The difference between the different variables used in the history of the registry were examined, and the quality of data in the birth registry from 1974-1981 was examined and compared to subsequent years. Data on birth weight and gestational age in the early years of the registry is inconsistent, and the identification of children born SGA is inaccurate, with 49 % false-positives. The biggest source of error is due to the rough and inaccurate intervals used for gestational age. By using –3 standard deviations as a cut-off for the identification of children born SGA, the number of false-positives was reduced to 9%, while the amount of false-negatives were increased. Conclusion: Choosing –3 standard deviations for identifying children born SGA is a viable, though not optimal solution fo

Estimation of SGA misclassification of children born in 1974–77.

<p>The births in 1979 with gestational age 38–45 were classified as SGA using - 2SD and - 3SD thresholds. The week specific thresholds (expected SGA) as well as common 40 week thresholds (observed SGA) were used. Use of the - 2SD threshold yielded both false positives and false negatives. Use of the - 3SD threshold greatly reduced the number of false positives. Week 44 and 45 are not shown due to the small amount of children born these weeks.</p

Percentage of children born SGA.

<p>Percentage of children born SGA.</p

Expected and observed number of children in each gestational age interval group, children born 1974–1977.

a<p> <i>Compared to observed values in 1978.</i></p

Birthweight on children with and without data on gestational age.

<p>Birthweight on children with and without data on gestational age.</p

Histograms of birthweight in 1979 and 1996.

<p>Values divisible by 50 and 100 continued to dominate in spite of coding of birthweight was done in 1-gram intervals since 1992.</p

Mean birthweight of children born 1974–1977 in each gestational age interval group.

a<p> <i>Given the distribution of birthweight in 1978.</i></p

Mean BW per year.

<p>Gestational age specific birthweight in the period 1974 to 1996. A gradual increase is seen. Gestational age was coded in the variable <i>fuldb</i> during the years 1974 to 1977. <i>fuldb0</i> meant ≥40 weeks and <i>fuldb1</i> meant 39 weeks. In reality, it appears that the mean gestational age of the children coded 35 years ago as <i>fuldb0</i> was almost exactly 40 weeks and the children coded as <i>fuldb1</i> was between 37 and 38 weeks.</p