Type of Delivery and Infant Brain Injury, 3/2000

In difficult labors, particularly women who have never delivered an infant ("nulliparous"), the health of the mother and of the infant is an issue of immediate concern to the obstetrician. Should vaginal delivery without assistance ("spontaneous delivery") continue to be pursued and for how long? Should vaginal delivery with assistance ("operative vaginal delivery" using either forceps or a vacuum extractor) be initiated? Should cesarean delivery be performed? What are the relative risks of injury to the infant associated with each of these alternatives? One of the hallmarks of injury to the infant brain associated with a difficult labor is intracranial hemorrhage, a prominent cause of cerebral palsy.

Dr. Dena Towner and her colleagues reviewed the records of 583,000 infants born to first time mothers between 1992 and 1994. ¹

Up to 25% of nulliparous pregnant women in difficult labor have operative vaginal delivery in which forceps or a vacuum extraction device was used. The vacuum extractor is essentially a gentle suction device attached to the infant's head and like forceps, guides the head through the birth canal. There continues to be a steady increase in the use of forceps or a vacuum device in difficult labors with a resulting controversy about whether they increase the risk of serious injury to the infant. This study was done to evaluate the complications of these various approaches for delivery in women having difficult labor.

The study showed that the rate of hemorrhage in the baby's brain is increased when vacuum extraction, forceps or caesarian section is used during labor. The rate of hemorrhage is not increased if the mother has a caesarian section before labor or has a spontaneous vaginal delivery. Thus, it is concluded that the difficult labor itself is probably one major factor in causing the infant brain hemorrhage; the type of delivery method used did not appear to have an important influence on the rate of hemorrhage in infants born to women with difficult labor.

To put it another way, the cause and occurrence of the prolonged and difficult labor (e.g. the position of the fetal head in the birth canal) may be the critical factor causing bleeding inside the fetal skull rather than the delivery procedure used.

Comment: Once a women goes into labor and the labor becomes difficult and prolonged, critical decisions have to be made jointly by the mother and the physician about what to do. A number of delivery alternatives are available, each of which is usually successful but each of which has risks--particularly to the infant. This study of a large population of pregnant women utilizing a very good database is providing some of the best information available about recent experience in the U.S.A. However, the specific reasons used by the obstetrician for choosing the particular intervention was not recorded and may be of importance in evaluating the outcome of the procedure used.

The editorial discussion accompanying the published paper re-emphasizes that in difficult labor, both caesarian section and operative vaginal delivery increase the risk of intracranial hemorrhage in the infant--but it also emphasizes again that the increased risk could very well be the result of the reasons for the difficult labor, rather than the method of delivery that was used. To quote the editorial comment: "--it appears that attempts at vaginal delivery with the use of either forceps or a vacuum device, if successful, carry no risk of fetal intracranial injury specific to the procedure used. When the chances of successful (vaginal) operative delivery are thought to be low, however, it should probably not be attempted; nor should repeated attempts at vaginal delivery be made if either vacuum extraction or forceps delivery has failed." The alternative that needs to be considered is caesarian section.

What is still lacking are definitive criteria rather than a judgement call about when to intervene in a difficult labor, and what are the specific criteria that should dictate the choice of the three available options: forceps, vacuum extraction, caesarian section. The published study is a valuable contribution, but it also identifies the need for more information.

¹ Towner D. et al. Effect of mode of delivery in nulliparous women on neonatal intracranial injury. NEJM 1999; 341:1709-1714. Editorial comment by Benedetti T.J. 341:1758-1759