News Release

Study finds an association between day of delivery and maternal-fetal mortality

Peer-Reviewed Publication

Society for Maternal-Fetal Medicine

In a study to be presented Friday, Jan. 27, in the oral concurrent session at 1:15 p.m. PST, at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting™, researchers with the Baylor College of Medicine in Houston, Texas, presented the study titled Association between day and month of delivery with maternal-fetal mortality: weekend effect and July phenomenon in current obstetric practice.

Based on data from the Centers for Disease Control and Prevention, the United States maternal mortality ratio is three to four times higher than that of most other developed nations. The maternal mortality ratio is increasing, reaching 21-22 per 100,000 live births in 2014 (more than double from 1990.) Although much has been written about this problem, few solutions have been forthcoming.

The researchers of this study wanted to know if maternal and fetal death ratios were higher on weekends versus weekdays or during different months of the year. "We were interested in this study because we believe this data provides a valuable window into the problems with the U.S. system of obstetric care delivery," said Amirhossein Moaddab, M.D., with the department of obstetrics and gynecology at Baylor College of Medicine and the presenter of the study at the SMFM annual meeting.

The researchers analyzed more than 45 million pregnancies in the U.S. between 2004 and 2014 to determine if there are significant differences in ratios of both maternal deaths and stillborn deliveries depending on the day they occurred. Weekend delivery is also associated with differential maternal and neonatal morbidity, including increased ratios of perineal lacerations, maternal transfusions, neonatal intensive care admissions, immediate neonatal ventilation requirements, neonatal seizures and antibiotic use.

"We were able to control for pregnancy complications, and found that most women with pregnancy complications known to lead to death actually deliver on weekdays, suggesting that the actual problem with weekend deliveries is even greater," Steven L. Clark, M.D., senior author of the study explained. Researchers also looked at months of the year including "July phenomenon," the month of the year that is associated with an increased risk of medical errors and surgical complications that occurs in association with the time of year in which United States medical school graduates begin residencies. The researchers found no association between maternal-fetal mortality and July.

Clark continued, "Any system that shows this sort of variation in the most important of all system outcomes is, by definition, badly broken. Our data suggest that a part of the overall dismal U.S. obstetric performance may be related to this systems issue, that is, there may be a 'spill over' effect that is demonstrably worse on weekends but is also present on weekdays to a lesser extent. Our data does not allow us to go any further than this in terms of specifying what the problem is. However, we believe it is likely due to the fact that rarely is care of the pregnant inpatient the primary concern of the treating physician - it is almost always a distraction from office, surgery or personal activities."

The researchers determined that by addressing this study and improving the obstetric quality of care on weekends by different methods, such as expanded use of the hospitalist or laborist model, will be one important component of addressing this issue.


A copy of the abstract is available at and below. For interviews please contact Vicki Bendure at 202-374-9259 (cell).

About the Society for Maternal-Fetal Medicine

The Society for Maternal-Fetal Medicine (est. 1977) is the premiere membership organization for obstetricians/gynecologists who have additional formal education and training in maternal-fetal medicine. The society is devoted to reducing high-risk pregnancy complications by sharing expertise through continuing education to its 2,000 members on the latest pregnancy assessment and treatment methods. It also serves as an advocate for improving public policy, and expanding research funding and opportunities for maternal-fetal medicine. The group hosts an annual meeting in which groundbreaking new ideas and research in the area of maternal-fetal medicine are shared and discussed. For more information visit

Abstract 59 Association between day and month of delivery and maternal-fetal mortality: weekend effect and July phenomenon in current obstetric practice
Amirhossein Moaddab, Christina M. Davidson, Haleh Sangi-Haghpeykar, Gary A. Dildy, Michael A. Belfort, Steven L. Clark Baylor College of Medicine, Houston, TX

OBJECTIVE: To compare maternal mortality ratio (MMR) and fetal mortality ratio (FMR) by day of death or delivery and month of delivery in the United States.

STUDY DESIGN: In a population-level analysis study, all maternal deaths based on death certificates data for United States residents between 2003-2013 were extracted from the CDC WONDER. We used live births and fetal deaths data from CDC-NCHS. We calculated and compared MMR (per 100,000 live births) and FMR (per 1,000 live births) by day and month of maternal death and of stillborn fetal delivery.

RESULTS: A total of 7,210 maternal deaths, 277,886 fetal deaths, and 45,138,496 live births were reported. 1,933 deaths occurred on weekends and 5,277 deaths occurred on weekdays. During the same period of time, 65,455 and 212,431 cases of fetal demise were delivered on weekends (S-S) and on weekdays (M-F), respectively. Saturday (20.7) and Sunday (22.1) had the highest MMR while Tuesday (13.2) had the lowest MMR. MMR was significantly higher on weekends than weekdays (21.4 vs. 14.6, p<0.001) demonstrates MMR and FMR for weekdays and weekends. The probability of maternal mortality was highest in March (17.2) and December (17.1) while August (14.8) and September (15.1) had the lowest probability for maternal mortality. When compared by month, no pattern was seen; neither maternal mortality (15.7 vs. 16.0, p¼0.59) nor delivery of stillborn fetus (6.16 vs. 6.15, p=0.94) in July were higher than ratios in other months.

CONCLUSION: Our data demonstrate a dramatic increase in U.S. MMR on weekends, despite a likely systematic bias toward admission and delivery of more complex patients on weekdays. A similar phenomenon was seen for stillbirths, although this association may have been impacted by a delay between death and delivery. This data suggests that the U.S. system of obstetric care delivery itself plays a significant role in known maternal and possibly fetal outcomes disparities between the U.S. and other high income countries. No July phenomenon was found for either maternal or fetal mortality.

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