Intrauterine fetal death and risk of shoulder dystocia at delivery.
BACKGROUND
Vaginal delivery is recommended after intrauterine fetal death. However, little is known about the risk of shoulder dystocia in these deliveries. We studied whether intrauterine fetal death increases the risk of shoulder dystocia at delivery.


METHODS
In this population-based register study using the Medical Birth Registry of Norway, we included all singleton pregnancies with vaginal delivery of offspring in cephalic presentation in Norway during the period 1967-2012 (n = 2 266 118). Risk of shoulder dystocia was estimated as absolute risk (%) and odds ratio with 95% confidence interval. Adjustment was made for offspring birthweight (in grams). We performed sub-analyses within categories of birthweight (<4000 and ≥4000 g) and in pregnancies with maternal diabetes.


RESULTS
Shoulder dystocia occurred in 1.1% of pregnancies with intrauterine fetal death and in 0.8% of pregnancies without intrauterine fetal death (p < 0.0001) (crude odds ratio 1.5, 95% confidence interval 1.2-4.9). After adjustment for birthweight, the odds ratio was 5.9 (95% confidence interval 4.7-7.4). In pregnancies with birthweight ≥4000 g, shoulder dystocia occurred in 14.6% of pregnancies with intrauterine fetal death and in 2.8% of pregnancies without intrauterine fetal death (p < 0.001) (crude odds ratio 5.9, 95% confidence interval 4.5-7.9). In pregnancies with birthweight ≥4000 g and concurrent maternal diabetes, shoulder dystocia occurred in 57.1% of pregnancies with intrauterine fetal death and 9.6% of pregnancies without intrauterine fetal death (p < 0.001) (crude odds ratio 12.6, 95% confidence interval 5.9-26.9).


CONCLUSIONS
Intrauterine fetal death increased the risk of shoulder dystocia at delivery, and the absolute risk of shoulder dystocia was particularly high if offspring birthweight was high and the mother had diabetes.
Department of Obstetrics and Gynecology, Akershus University Hospital, Lørenskog, Norway.|Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
Sandra
http://orcid.org/0000-0002-9238-5344
S
Larsen
Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
Joanna
http://orcid.org/0000-0002-5739-3699
J
Dobbin
Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
Oliver
http://orcid.org/0000-0002-5977-812X
O
McCallion
Department of Obstetrics and Gynecology, Akershus University Hospital, Lørenskog, Norway.|Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
Anne
http://orcid.org/0000-0002-2756-1583
A
Eskild
D000328:Adult; D001724:Birth Weight; D036861:Delivery, Obstetric; D004420:Dystocia / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D005313:Fetal Death; D006801:Humans; D007231:Infant, Newborn; D016015:Logistic Models; D009664:Norway; D016017:Odds Ratio; D011247:Pregnancy; D012042:Registries; D012307:Risk Factors; D012782:Shoulder
Birthweight; diabetes; intrauterine fetal death; pregnancy; shoulder dystocia