Skip Internal Navigation
EB Research - Perinatal Epidemiology
Consortium on Safe Labor (CSL)
In the past half century, labor and delivery practice has followed the Friedman curve in the United States. However, the obstetric population and labor management have changed substantially during the same period. Mounting evidence has begun to suggest that the Friedman curve may no longer be appropriate for contemporary labor practice. New, evidence-based definitions of labor protraction and arrest are needed. In addition, our understanding of the reasons behind the rising cesarean section rate was incomplete because detailed information on labor and delivery was lacking at a national level. The primary goals of this observational study were:
- Explore the underlying causes of the high cesarean rate in the U.S. population;
- Describe contemporary labor progression at the national level; and
- Determine when is the more appropriate time to perform a Cesarean delivery in women with labor protraction and arrest.
The CSL collected detailed information from electronic medical records in 228,562 deliveries from 19 hospitals across the U.S. from 2002 to 2008. The most common reason for cesarean section was elective repeat cesarean delivery due to a previous uterine scar, accounting for approximately one third of all cesarean deliveries. However, investigators also found that one out of three first time mothers was delivered by cesarean section and a high percentage of intrapartum cesarean deliveries were performed too soon before women achieved active labor. These findings mean that preventing cesarean delivery in the first pregnancy will go a long way to decrease the national cesarean delivery rate. In another major study from the CSL, labor patterns were found to be different for individual women. Many parturients did not have a clear pattern of active phase, and more importantly, the active phase of labor may not start until 6 cm of cervical dilation or later. This finding differs from the prevailing concepts established by the Friedman curve which illustrated that the active phase starts before 4 cm dilation. Researchers have also compared the differences in labor patterns using data from the CSL of women who presented in labor for delivery and compared them to women from the Collaborative Perinatal Project, another NIH sponsored study from the late 1950's to early 1960s. Labor patterns were found to be longer now than approximately 50 years ago. Researchers have also examined other factors that may affect labor progression and cesarean delivery, such as induction of labor, maternal obesity, and epidural analgesia for labor pain. Other areas of ongoing research include determining the optimal time for second stage of labor, when pushing begins, and exploring how the sociodemographic changes in the current obstetrical population have affected pregnancy complications, maternal and neonatal morbidity, and implications for clinical management including delivery timing and route. Researchers are exploring how chronic diseases such as hypertension, diabetes and asthma also affect these outcomes. Further work from the CSL study will help shape the future clinical care of pregnant women.
The CSL data is publically available via the NICHD DASH website:
Una Grewal, Ph.D., M.P.H. &
Katherine Laughon Grantz, M.D., M.S.
- Kim SS, Zhu Y, Grantz KL, Hinkle SN, Chen Z, Wallace M, Smarr MM, Epps NM, Mendola P. Obstetric and Neonatal Risks Among Obese Women Without Chronic Disease.
Obstetrics & Gynecology. 2016 Jul;128(1):104-12.
- Grantz KL, Gonzalez-Quintero V, Troendle J, Reddy U, Hinkle SN, Kominiarek M, Zhang, J. Labor Patterns in Women Attempting Vaginal Birth After Cesarean With Normal Neonatal Outcomes.
American Journal of Obstetrics & Gynecology, 2015 Aug;213(2):226.e1-6. PMID: 25935774
- Mendola P, Mumford SL, Mӓnnistӧ TI, Holston A, Reddy UM, Laughon SK. Controlled Direct Effects of Preeclampsia on Neonatal Health After Accounting for Mediation by Preterm Birth.
Epidemiology. 2015 Jan;26(1):17-26.
- Parikh LI, Männistö T, Mendola P, Sjaarda LA, Hinkle SN, Lu Z, Chen Z, Reddy UM, Laughon SK. Neonatal outcomes in early term birth.
American Journal of Obstetrics & Gynecology. 2014 Sep;211(3):265.e1-11.
- Laughon SK, Berghella V, Sundaram R, Reddy UM, Lu Z, Hoffman MK. Neonatal and maternal outcomes with prolonged second stage of labor.
Obstetrics & Gynecology. 2014 Jul;124(1):57-67.
- Mendola, P.; Laughon, S.K.; Männistö, T, Leishear, K.; Reddy, U.M., Chen, Z., Zhang, J. Obstetric complications among US women with asthma.
Am J Obstet Gynecol 208:127.e1-8, 2013.
- Männistö, T.; Mendola, P.; Reddy, U.; Laughon, S.K. Neonatal outcomes and birth weight in pregnancies complicated by maternal thyroid disease.
Amer J Epidemiol 2013; doi: 10.1093/aje/kwt031.
- Männistö, T.; Mendola, P.; Grewal, J.; Xie, Y.; Chen, Z.; Laughon, S.K. Thyroid diseases and adverse pregnancy outcomes in a contemporary obervational cohort from the United States.
J Clin Endocrinol Metabolism 2013; early release June 6, 2013. doi:10.1210/jc.2012-4233.
- Mendola, P.; Männistö, T.; Leishear, K.; Reddy, U.M.; Chen, Z.; Laughon, S.K. Neonatal health of infants born to mothers with asthma.
J Allergy Clin Immunol (In Press)
- Werder E, Mendola P, Männistö T, O'Loughlin J, Laughon SK. Effect of maternal chronic disease on obstetric complications in twin pregnancies in a U.S. cohort.
Fertility and Sterility. 2013;100(1):142-149.e2.
- Bowers K, Laughon SK, Kim SD, Mumford SL, Brite J, Kiely M, Zhang C. The association between a medical history of depression and gestational diabetes in a large multi-ethnic cohort of the United States.
Paediatric and Perinatal Epidemiology, 2013; 27:323-328.
- Bowers K, Laughon SK, Kiely M, Brite J, Zhang C. Gestational diabetes, pre-pregnancy obesity, and pregnancy weight gain in relation to excess fetal growth: variations by race/ethnicity.
Diabetologia, 2013; 56(6):1263-71.
- Reddy UM, Zhang J, Sun L, Chen Z, Raju TNK, Laughon SK. Neonatal mortality by attempted route of delivery in early preterm birth.
American Journal of Obstetrics & Gynecology, 2012; 207:117.e1-8.
- Laughon SK, Zhang J, Grewal J, Sundaram R, Beaver J, Reddy UM. Induction of labor in a contemporary obstetric cohort.
American Journal of Obstetrics & Gynecology, 2012; 206:486.e1-9.
- Laughon SK, Branch DW, Beaver J, Zhang J. Changes in labor patterns over 50 years.
American Journal of Obstetrics & Gynecology, 2012; 206(5):419.e1-9.