Infants born at night have higher mortality rate in first month of life

Jeffery Gould

Babies born at night in California have a significantly greater risk of dying within their first four weeks than do babies born during the day, according to a new study headed by a researcher at the School of Medicine and Lucile Packard Children's Hospital. The difference persists even when adjustments are made to account for differences in birth weight, pregnancy and delivery complications that might occur between night and day.

The authors speculate that the increase in mortality risk, which accounts for nearly 10 percent of neonatal deaths in California, might be due to poorer staffing coverage or a decreased availability of services at night. Identifying and correcting such problems might be a potent way to reduce the deaths of newborn infants, they said.

"If I told you I had a drug that would decrease infant mortality by 5 to 10 percent, it would be huge news," said neonatologist Jeffery Gould, MD. "We have a tremendous opportunity to improve things here." Gould, the Robert L. Hess Professor in Pediatrics, is the first author of the paper published in the August issue of Obstetrics and Gynecology.

The researchers collected birth and death data on more than 3.3 million infants born in California between 1992 and 1997. The overall neonatal mortality rate in the state was 2.08 deaths for every 1,000 live births. When categorized according to the time of day, babies born in the early night between 7 p.m. and 1 a.m. were 12 percent more likely to die within the first month than were babies born between 7 a.m. and 7 p.m. Those born in the late night, between 1 and 7 a.m., were 16 percent more likely to die.

Although several previous European studies reported that nighttime births carry an increased risk of death, those studies failed to investigate whether more high-risk deliveries occurred at night. If so, the increase in mortality could be due to more complicated deliveries and sicker babies, rather than to a correctable, nighttime-specific problem.

Gould and his colleagues found that the differences between night and day remained even when the statistical model was adjusted to take into account some common factors that can affect a newborn's health: timing of prenatal care initiation; complications such as high maternal blood pressure, diabetes, placenta previa or abruption; and the infant's gender and birth weight.

The researchers wondered whether the nighttime increase in risk was related to provider fatigue or to staffing and transport issues at California hospitals. They found that although the likelihood of death was higher in the late night than the early night, the overall difference wasn't significant enough to point a finger at overly sleepy doctors and nurses.

In contrast, when the hospitals in which the infants were born were separated by the levels of care they provide, the researchers found a striking difference. Nighttime infants born at primary care hospitals, which typically handle the least complicated deliveries, were no more likely to die than those born during the day. Those born at hospitals providing more sophisticated levels of care, however, were at a significant disadvantage at night.

In particular, those born in the late night at intermediate-level facilities (those capable of handling sicker infants but not providing ventilation) or community-level facilities (those capable of providing long-term ventilation but not major surgery) were 33 and 21 percent more likely to die, respectively. Those at regional hospitals providing the highest level of care were at 14 percent greater risk.

The researchers found that more complicated births, such as multiples or very low birth-weight infants had a lower increase in mortality than did supposedly uncomplicated single births, suggesting that physicians and support staff were able to identify and respond to high-risk situations, but may be less likely to appropriately manage emerging problems during a low-risk nighttime delivery.

The authors plan to conduct further research to determine whether the particularly large increase at intermediate care facilities is due to late night difficulties in transporting a newborn infant with breathing difficulties to a higher-level nursery at another hospital or to inadequate nighttime staffing or support services. They will also analyze the data to determine if and why some hospitals have higher mortality rates than others.

"Our findings suggest that this is something to be concerned about," said Gould. "Now that this issue is on the table, we expect people to respond."