LAS VEGAS – Weekend deliveries were associated with a significantly increased risk of maternal-fetal morbidity and death, according to a review of all U.S. deliveries over the past decade.

“Maternal morbidity and mortality were increased on weekends, compared to weekdays, and stillbirth and neonatal morbidity were also increased in infants delivered on weekends. Both of these findings occur against a background of lower intrinsic risk among weekend deliveries,” Amirhossein Moaddab, MD, said at the annual Pregnancy Meeting sponsored by the Society for Maternal-Fetal Medicine.

“Any system that shows this sort of variation in the most important of all system outcomes is, by definition, badly broken,” senior author Steven L. Clark, MD, said in a press release about the study. “Our data suggest that a part of the overall dismal U.S. obstetric performance may be related to this systems issue.”

Study objectives included measuring both maternal and fetal mortality ratios by the day and month of death or delivery; the study also tracked maternal and neonatal morbidities according to the day of the week the delivery occurred.

Using publicly available data sets (the National Vital Statistics System and the Centers for Disease Control and Prevention WONDER online database), Dr. Moaddab and his colleagues examined all live births and all maternal and fetal deaths in all 50 states and the District of Columbia for the period from 2004 to 2014.

In total, there were 45,036,622 live births, 7,551 maternal deaths, and 275,914 stillbirths during this period.

On weekdays, the maternal mortality rate was 15.3/100,000 live births; the rate rose to 22.8 maternal deaths per 100,000 live births on the weekends (P less than .001). Fetal mortality followed a similar pattern: The weekday fetal mortality rate was 5.85/1,000 live births, compared with 7.21/1,000 live births on the weekends (P less than .001).

A wide range of maternal and fetal morbidities were also more common when deliveries happened on the weekend. For mothers, the adjusted relative risk (aRR) ranged from 1.41 for maternal transfusion to 1.166 for perineal lacerations with Saturday or Sunday deliveries. Unplanned hysterectomy, however, was less likely on the weekend (aRR, 0.810).

Neonatal morbidities with a higher adjusted relative risk included gestational age less than 28 weeks (aRR, 1.481), a 5-minute Apgar score less than 7 (aRR, 1.251), and being placed on a ventilator or admitted to the neonatal intensive care unit (aRRs, 1.219 and 1.199, respectively). The odds of having a chromosomal abnormality were lower for infants delivered on weekends (aRR, 0.864), a result consistent with the increased likelihood of planned delivery for fetuses whose chromosomal status was known, said Dr. Moaddab, a postdoctoral fellow in obstetrics and gynecology at the Baylor College of Medicine, Houston .

Examining maternal characteristics, Dr. Moaddab and his colleagues did find some significant differences between those delivering on weekdays and weekends. However, because the weekend group was healthier overall than the weekday group, these differences were not likely to account for the worse weekend outcomes.

“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 total problem with weekend deliveries is even greater,” said Dr. Clark, professor of ob.gyn. at Baylor College of Medicine.

For example, women delivering on weekends were less likely to be smokers, have diabetes or gestational diabetes, or have chronic or gestational hypertension; they were also less likely to have had a previous cesarean delivery (all P equal to or less than .0001). They were, however, more likely to be nulliparous and to have eclampsia (P equal to or less than .0001).

Dr. Moaddab said that his group’s examination of monthly variations in maternal and fetal morbidity and mortality showed no sign of the “July phenomenon,” the worsening in outcomes seen in some specialties when new interns take to the wards and clinics.

The “weekend effect,” said Dr. Moaddab, has been documented elsewhere as well. In the United Kingdom, a recent observational study of obstetric outcomes found “increases in the rates of death and other complications for both women and babies born at weekends,” he said (BMJ. 2015;351:h5774).

Though Dr. Moaddab’s descriptive study couldn’t get at underlying causes, he said that there are many possible culprits. These can include the divided physician attention and reduced provider availability that can come with weekend staffing, as well as the possibility that the experience level of both physician and nurse staff drops on weekends. Long work hours that come with call may also contribute, he said.

The study authors reported no outside sources of funding and no conflicts of interest.

koakes@frontlinemedcom.com

On Twitter @karioakes

Weekend births linked to higher maternal-fetal mortality