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Prognosis for Spontaneous Labor in Women with Uncomplicated Term Pregnancies
Abstract & Commentary
By John C. Hobbins, MD, Professor and Chief of Obstetric, University of Colorado Health Sciences Center, Denver, is Associate Editor for OB/GYN Clinical Alert.
Synopsis: Maternal and fetal morbidity in low-risk patients entering the hospital in spontaneous labor at term is extremely low and this can be kept in mind when patients are considering planned cesarean section for non-medical reasons.
During the last two months an unusual number of papers were published which, while not having earth-shaking scientific value, should have some clinical impact. Although the OB/GYN Clinical Alert format requires reviewing one article, I have decided this month (only) to attempt three "quick hits" so that more than one message can be conveyed.
Let's start with a no-brainer. In the April issue of Obstetrics & Gynecology, a group from Dallas studied 103,566 low-risk patients delivering between 1988 and 2006 who were at term (37-41 weeks) and who entered in spontaneous labor. Ninety-six percent had vaginal deliveries. Not surprisingly, nulliparas had higher rates of forceps deliveries (8% vs 1%), cesarean deliveries (8% vs 2%), and third- and fourth-degree lacerations (13% vs 2%), while multiparas had a higher rate of macrosomia (9% vs 4%).1
Most importantly, the overall perinatal mortality rate was only 0.3 rate per 1000 births in this group of low-risk patients. Low five-minute Apgar scores were very rare (1.5 per 1000), as were cord blood pH < 7.0 (3 per 1000) and admissions to the NICU (4 per 1000).
The authors pointed out that "virtually all of the above women" (representing about 4 out of 10 deliveries at Parkland Hospital) "can anticipate safe vaginal deliveries for themselves and their infants."
The second study, published in the April 2009 issue of the American Journal of Obstetrics & Gynecology, demonstrated the value of adding glucose to IV fluids during labor.2 Since skeletal muscle works better when individuals undergoing prolonged exercise are adequately hydrated and loaded with carbohydrate, the authors postulated that the smooth muscle of the uterus would respond similarly during labor. The group randomized 300 women in labor with IV drips in place to one of three groups: normal saline (84), 5% dextrose/saline (D/S) (76), or 10% dextrose/saline (72).
The length of the second stage of labor almost doubled in those without the glucose (106 min vs 69 min with 5% D/W and 62 min with 10% D/S). Also, the incidence of prolonged labor (> 12 hrs) was much higher in the saline-only group (22% vs 9.3% and 6.8%, respectively).
Lastly, in other OB/GYN Clinical Alerts, the evils of smoking in pregnancy have been touched upon, as well as the benefits of quitting — even when using nicotine substitutes. In a recent issue of the British Medical Journal, a group from New Zealand and Australia published a collaborative study comparing outcomes in women who were nonsmokers (1992), stopped smoking before 15 weeks (261), and continued smoking (251).3
The results were dramatic. Those who stopped smoking before 15 weeks had no difference in rates of preterm birth and intrauterine growth restriction (IUGR), compared with nonsmokers (4% vs 4% and 10% vs 10%, respectively). However, there were statistically significant differences in these outcomes between those who quit smoking compared with those who did not. Smokers had rates of preterm birth of 10% (vs 4%) and IUGR of 17% (vs 10%).
The Dallas group acknowledged in their paper that their population has a lower percentage of "uncomplicated" pregnancies (37%) than the 50% incidence estimated by the CDC or from data from the state of Massachusetts between 1995 and 2005. The authors point out that these women who do not have a compelling medical reason for having a cesarean section are the ones who might be considering a planned primary section, a practice that occurred in 20% of low-risk women in the United States in 2006.
At the recent meeting of the Society for Maternal-Fetal Medicine, Olson et al presented data from a California state database showing that those low-risk women who had planned cesarean sections had a 10- to 20-fold increase in cardiac complications, a 4- to 8-fold increase in major maternal infection, and a 3-times greater risk of anesthetic complications.4 Also, there was a higher rate of combined neonatal morbidity, which included increased rates of RDS and transient tachypnea of the newborn (TTN). When one considers that there is a tendency now to plan elective deliveries earlier (37% of elective repeat cesarean sections in 2007 were carried out before 39 weeks5), then there is even greater potential for unnecessary maternal and neonatal morbidity. The Dallas data can serve as a guideline for patients to use for comparison when considering elective primary cesarean section.
Regarding the paper on intravenous dextrose in labor, I have no idea how many hospital use saline alone for maternal hydration, but this article strongly suggests that there is benefit of 5% D/S, but no real advantage to 10% D/S.
We have had many women who quit smoking after the first trimester, and yet, on ultrasound scans, their placentas in the second and third trimester often are heavily laced with calcium. It is heartening to know that, despite this observation, some neonatal outcomes are no worse than those seen in nonsmokers.