Short summary

The risk of stillbirth increases after 37-38 weeks of gestation and accelerates after 40 weeks. Some subgroups of pregnant women are known to have an increased risk of stillbirth and we hypothesize that their excess risk increases further in term and postterm pregnancies. The aim of this project is therefore to study the association between perinatal mortality and maternal BMI, age, parity, smoking and a history og cesarean section.

Rationale

The rate of stillbirths at term and postterm in Denmark is about 5 ‰ although there is a wide variation between gestational weeks. In gestational week 37 the risk of stillbirth is 0,37 ‰ whereas the risk in week 41 is almost 2 ‰ (pregnancies at risk). Therefor guidelines in Denmark recommend labor induction no later than week 41+5 for low risk women, and earlier for high risk women, e.g. obese women and women of 40 years or older. Studies have suggested that this practice compared to expectant management has decreased the rate of perinatal mortality. As this practice has an impact on hospitals costs and the women's chance to give birth spontaneously more knowledge about the risk of stillbirth and perinatal mortality at term and postterm is important.

Studies have supported an association between an excess risk of stillbirth and maternal obesity, smoking and age. It has also been suggested that parity and a history of cesarean section contributes to the statistics.

Some studies have reported that the excess risk of stillbirth for obese women is increasing in postterm pregnancies. We don't know, though, if this is also the case in other subgroups of pregnancies. Therefor the aim of this project is to study the association between perinatal and neonatal mortality and maternal BMI, age, parity, smoking and a history of cesarean section.

Description of the cohort

All singleton births in Denmark, 2000-2014 delivered from gestational week 37 (about 900.000). 

Data and biological material

Data from the Danish Birth Register:

Maternal data:

Date of birth, BMI, Parity, Smoking status, History of cesarean section, Ultrasound, Hypertensive diagnosis, Diabetes

Infant data:

Sex, Date of birth, Apgar score, Weight, Height, Gestational age, Date of death, stillborn yes/no

Collaborating researchers and departments

Department of Gynaecology and Obstetrics, Odense University Hospital and Institute of Clinical Research, University of Southern Denmark:

• Student of health science, midfiwery,  Julie Anja Ribe Bagge
• Professor Ellen Aagaard Nøhr, Ph.D., MH.Sc.
• Postdoc Helene Kirkegaard, Ph.D., MH.Sc.

University of Southern Denmark

• Biostatistician and associate professor, PhD, Sören Möller