Are Complete Blood Cell Counts Useful in the Evaluation of Asymptomatic Neonates Exposed to Suspected Chorioamnionitis?

Abstract

Radiation exposure of prepubertal, adolescent, and pregnant females may increase the risk of a low-birth-weight (LBW) infant weighing less than 2500 g. It is not clear whether radiation has direct effects on the reproductive organs or influences outcomes indirectly through altering thyroid function. Diagnostic dental radiographs deliver low radiation doses to the hypothalamus-pituitary-thyroid axis but not the reproductive structures or fetus. This population-based case-control study examined the effects of dental radiography in women enrolled in a dental insurance plan who had live singleton births in the years 1993-2000. The case group included 1117 women having live singleton births of a LBW infant. Nearly one third of these infants were born at term. The latter infants, born at 37 or more weeks gestation, had birth weights of 1501-2499 g. Each case was matched with 4 control pregnancies resulting in a normal-birth-weight term infant. The age range was 12-45 years.Dental radiography was independent of numerous risk factors for LBW infants. Exposures were more frequent for women having LBW infants than in control women. Of women delivering a LBW infant, 1.9% had received more than 0.4 mGy of radiation, compared with 1.0% of control women. The frequency of exposures exceeding 4 mGy in women delivering a term LBW infant was 3.0%, significantly higher than in the control group. This level of radiation was recorded for 1.6% of women having a preterm LBW infant and 1.0% for those having a VLBW infant (1500 g or less)-not significantly different from the prevalence in women with normal-birth-weight infants. The adjusted odds ratio for a LBW infant in women exposed to more than 4.0 mGy, compared with unexposed women, was 2.27. The figure for women exposed to 0.1-0.4 mGy was 1.20. Considering radiation dose as a continuous variable, an increase of 1 mGy correlated with a 1.83-fold greater chance of a LBW infant. Odds ratios for VLBW and preterm LBW infants were not significantly associated with radiation doses higher than 0.4 mGy. Radiation exposure was, however, strongly associated with birth of a term LBW infant. The odds ratios for VLBW infants and preterm LBW infants were 2.19 and 1.77, respectively. Compared with unexposed women, those exposed to more than 0.4 mGy had an adjusted odds ratio for a term LBW infant was 3.61, and the odds ratio for exposure to 0.1-0.4 mGy was 1.66. More than two thirds of all radiation exposures were delivered in the first trimester of pregnancy.Very low-dose radiation exposure of the maternal head/neck region during pregnancy is associated with an increased risk of having a LBW infant. It cannot be assumed that exposing nonreproductive organs to very-low-dose radiation during pregnancy is safe. EDITORIAL COMMENT(In prepubertal girls, high-dose therapeutic radiation for childhood cancers has been associated with an increased risk of future low-birthweight (LBW) offspring (Chiarelli AM, et al. ABSTRACTPregnancies after successful external cephalic version (ECV) are generally regarded a...

Role of Guidelines on Length of Therapy in Chorioamnionitis and Neonatal Sepsis

“…Overall, 18% of infants with culture-negative sepsis had a normal IT ratio as well as normal CRP at 12 hours of age. In the study by Jackson et al, 13 3 of 4 infants with positive blood culture results had no signs and symptoms of sepsis, and all 4 infants with positive blood culture results had an IT ratio ,0.2 at age 12 hours.…”

“…A massive sample size would be needed to prove that these infants do not require further treatment. Jackson et al 13 reported follow-up data on 98 asymptomatic infants with an abnormal IT ratio at 12 or 24 hours of life. These infants were discharged from the hospital with negative blood culture results after receiving antibiotics for 48 hours.…”

“…8 For interpretation of CBC, the COFN guidelines rely on data from a study by Manroe et al, 12 which is .3 decades old and has a small sample size of convenience with only a few infants with culture-proven sepsis. In a study by Jackson et al, 13 99% of infants exposed to CAM had at least 1 abnormal finding on the CBC during the first 24 hours of life. In a cohort of 3154 neonates, Murphy et al 14 found that ∼50% of infants had an abnormal IT ratio during the first 24 hours of life.…”

“…This low incidence of positive results is likely due to use of intrapartum antibiotics and is consistent with the literature. 13 Clinical signs of sepsis have been found to be a more sensitive indicator of early-onset neonatal sepsis than hematologic parameters. 4 In our cohort of 4 infants with a positive blood culture result, 3 infants were depressed at birth (2 required intubation and positive pressure ventilation, and 1 required continuous positive airway pressure) in the delivery room.…”

“…9 Replying to experts' concern, the COFN cited the study by Jackson et al, in which only 13% of asymptomatic infants had an elevated IT ratio at 12 hours, implying only a small number of infants would require additional treatment. 13,26 However, they continue to include the option of CRP analysis at 6 to 12 hours of life. Although our findings were similar regarding an abnormal IT ratio (14.9%) at 12 hours in neonates exposed to CAM, the addition of an abnormal CRP (22%) or abnormal CRP and/or IT ratio (27.6%) markedly increases the number of infants requiring prolonged antibiotics.…”