[Foetal Mortality in Singleton Foetuses at and beyond Term - An Analysis of German Perinatal Data 2004-2013]

Abstract

Background: Foetal mortality appears to increase in postmature pregnancies. There is debate on the optimal timing of induction of labour vs. watchful waiting. The literature on retrospective analyses of secondary data is inconclusive. Different approaches to calculate foetal risk exist. Recent and relevant data are needed in order to realise an appropriate discussion.

Material and methods: Mortality in singleton foetuses in Germany, between 2004 and 2013 was analysed in relation to gestational age. Risk for foetal death is described comparing stillbirths per 1,000 births at a particular gestational age (GA) vs. stillbirths per 1,000 ongoing pregnancies ("fetus-at-risk" model). Access to German routine perinatal data was granted. We included all stillbirths in singleton foetuses with no malformations after 36+6 weeks gestational age from 2004 until 2013.

Results: 5,933,117 births fulfilled our inclusion criteria. Foetal mortality per 1,000 births during that week of pregnancy is lowest between 41+0 and 41+6 days of (0.7/1,000). Mortality then increases to 2.3/1,000 in 42+0 to 42+6 GA. With the "fetus-at-risk" model, mortality is low between 37+0 and 39+6 GA, ranging from 0.2/1,000 ongoing pregnancies, increasing to 0.6/1,000 between 41+0 and 41+6, and 2.3/1,000 in the following week. For pregnancies lasting longer than 42+6 weeks, the stillbirth risk is identical at 6.3/1,000 with both calculation methods.

Conclusion: Fetal mortality is low until 41+6 weeks of pregnancy. Interpretation of current data does not support a policy of routine IOL before this gestational age in singleton foetuses.