In the United States, labor and delivery practices over the past half century have been dictated by Friedman’s curve, which represents the hours of labor plotted against cervical dilation. Changing obstetric populations and labor management has brought about a need to reassess these data for contemporary labor practice. New, evidence-based definitions of labor protraction and arrest are needed. Additionally, understanding of increasing national cesarean section rates was impeded by lack of detailed labor and delivery statistics.
BBB investigators are collaborating with Epidemiology Branch (EB) researchers on studies designed to address these issues. In particular, the Consortium of Safe Labor (CSL) collected detailed information from electronic medical records in 228,562 deliveries from 19 hospitals across the United States from 2002 to 2008. BBB researchers have 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 1950s to early 1960s.
Previous NICHD research found that labor patterns are longer now than approximately 50 years ago. Researchers also have 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 these studies will help shape the future clinical care of pregnant women.
Another issue of considerable interest in assessing labor progression, complications, and adverse pregnancy outcomes is that they often recur in subsequent pregnancies. In addition to recurrence of the same complication, an adverse outcome in one pregnancy also seems to increase risk for other adverse outcomes in subsequent pregnancies. However, data are limited to assess why some women have a recurrence of complications and adverse outcomes while others do not, and whether risk factors for recurrence are modifiable. Clinically, the best information available is prior pregnancy history; however, statistical methods for predicting recurrence and assessing risk are lacking.
The Consecutive Pregnancies Study, a unique collaborative effort between BBB and EB, was designed to:
- Estimate the association between the occurrence and timing of pregnancy/labor complications among consecutive pregnancies in women
- Examine the demographic and environmental factors that may influence these associations
- Further develop statistical methodology to study associations among multiple pregnancy outcomes
Repeat pregnancy data was collected on 114,679 pregnancies from 51,086 women, delivering ≥20 weeks of gestation from 20 hospitals in the state of Utah from 2002 to 2010.
BBB: Raji Sundaram, M.Stat., Ph.D.
- For CSL: Una Grewal, Ph.D., M.P.H., and Katherine Laughon Grantz, M.D., M.S.
- For the Consecutive Pregnancies Study: Katherine Grantz, M.D., M.S., and Edwina Yeung, Ph.D.
Lee, Y., Wang, M-C., Grantz, K. L., & Sundaram, R. (2019). Joint modeling of competing risks data and current status data: an application to spontaneous labour study. Journal of the Royal Statistical Society, Series-C, 68, 1167-1182.
Ma, L., & Sundaram, R. (2018). Analysis of gap times based on panel count data with informative observation times and unknown start time. Journal of the American Statistical Association, 113(521), 294-305.
Grantz, K. L., Sundaram, R., Ma, L., Hinkle, S., Berghella, V., Hoffman, M. K., & Reddy, U. M. (2018). Reassessing the duration of the second stage of labor in relation to maternal and neonatal morbidity. Obstetrics and Gynecology, 131(2), 345-353. PMID: 29324600. PMCID: PMC5785437
Sapra, K. J., Buck, L. G. M., Sundaram, R., Joseph, K. S., Bates, L. M., Galea, S., & Ananth, C. V. (2016). Signs and symptoms associated with early pregnancy loss: findings from a population-based preconception cohort. Human Reproduction, 31(4), 887-896. PMID: 26936888. PMCID: PMC4791918
Laughon, S. K., Berghella, V., Reddy, U. M., Sundaram, R., Lu, Z., & Hoffman, M. K. (2014). Neonatal and maternal outcomes with prolonged second stage of labor. Obstetrics and Gynecology, 124(1), 57-67. PMID: 24901265. PMCID: PMC4065200
Laughon, S. K., Zhang, J., Grewal, J., Sundaram, R., Beaver, J., & Reddy, U. M. (2012). Induction of labor in a contemporary obstetric cohort. American Journal of Obstetrics and Gynecology, 206(6), 486.e1-9. PMID: 22520652. PMCID: PMC3361637
Zhang, J., Troendle, J., Mikolajczyk, R., Sundaram, R., Beaver, J., & Fraser, W. (2010). The natural history of the normal first stage of labor. Obstetrics & Gynecology, 115(4), 705-710. PMID: 20308828
Zhang, J., Sundaram, R., Sun, W., & Troendle, J. (2008). Fetal growth and timing of parturition in humans. American Journal of Epidemiology, 168(8), 946-951. PMID: 18775925. PMCID: PMC2727206