Jóhanna Gunnarsdóttir^1,2

Jónína Rún Ragnarsdóttir³

Matthildur Sigurðardóttir²

Kristjana Einarsdóttir¹

 

¹Centre of Public Health Sciences, Faculty of Medicine, University of Iceland, Reykjavik, ²Department of Obstetrics and Gynecology, Landspitali National University Hospital of Iceland, Reykjavik, ³Faculty of Medicine, University of Iceland.

Correspondence: Jóhanna Gunnarsdóttir, johagunn@hi.is

Key words: Macrosomia, large for gestational age, labor induction, diabetes, post-term birth.

 

AIM: Diabetes and prolonged pregnancy are risk factors of macrosomia. The aim was to explore the relationship between the increased rate of labor induction and macrosomia in Iceland. Changes in the incidence proportion of macrosomia was estimated by gestational age. Further, the association between labor induction and macrosomia was estimated in reference to expectant management.

MATERIAL AND METHODS: Data from the Iceland birth registry on 92,424 singleton births from 1997 to 2018 was used in this cohort study. Macrosomia was defined as birth weight more than 4.5 kg. The incidence proportion during three periods, 1997-2004, 2005-2011, 2012-2018, was calculated and stratified by gestational age. The relative risk reduction of macrosomia over time was calculated with log-binomial regression, using the first period as reference. The risk and relative risk of macrosomia compared with expectant management was estimated and adjusted for diabetes.

RESULTS: The total number of macrosomic infants was 5110 and of those only 313 had a mother with diabetes. The incidence proportion of macrosomia was 6.5% during the period 1997-2004, but 4.6% during 2012-2018. A relative risk reduction of macrosomia over time was seen for deliveries after estimated due date. Labor induction decreased the risk of macrosomia, but the association persisted after adjustment for diabetes.

CONCLUSION: The rate of macrosomia decreased in Iceland during the last two decades, but only a small proportion of macrosomic infants had a mother with diabetes. Labor induction decreased the risk of macrosomia, an association which seemed independent of diabetes.

 

Table I. The risk of macrosomi (birth weight > 4.5 kg) according to maternal demographic in Iceland from 1997 to 2018.

Table II. Factors of delivery and neonatal complications according to maternal diabetes in Iceland from 1997 to 2018.

Figure 1. Indicence proportion of macrosomia and large for gestational age neonates that were born in Iceland from 1997 to 2018.

Figure 2. Labor induction in women with and without diabetes as a proportion of all singleton deliveries from 1997 to 2018.

Table III. Number of macrosomic neonates, incidence proportion and relative risk according to birth year periods, stratified by diabetes and gestational age.

Table IV. The risk of macrosomic births after labour induction compared with expectant management in a population of singleton term cephalic births between 2012 and 2018.