A 36 0/7 gestational age female was born to a G2P1 female with a history of preterm delivery. The mother was known to be Group B Streptococcus positive but was inadequately treated with intrapartum antibiotics because of late presentation for delivery. The infant had Apgar scores of 7 and 8, and was slightly dusky at delivery with some mild tachypnea.
The pertinent physical exam showed a small infant with growth parameters 1820 grams (<3% on Fenton Growth Chart), 30 cm head circumference (3-10%) and length of 43 cm (10%), with a Ballard score consistent with 36 week gestation. Respiratory rate was in the 40s/minute with a normal blood pressure, temperature and heart rate. Her examination showed no physical abnormalities including no murmur, or color changes
The diagnosis of of a small for gestational age, preterm infant was made. She was intermittently tachypneic so screening laboratory testing was done and antibiotics were started. The laboratory evaluation showed the capillary complete blood count with a hematocrit of 71%, hemoglobin of 22.3 gm/dL, white blood cell count of 14.6 x 1000/mm2, left shift of 9% and a platelet count of 287 x 1000/mm2. Her C-reactive protein was 0.6 mg/dl, with a glucose of 48 mg/dL. Over the next couple of hours her tachypnea resolved, she had one glucose that was 43 mg/dL which resolved with oral feeding, and her repeated venous complete blood count had a hematocrit of 62% and hemoglobin of 21.4 gm/dL.
Over the next 24 hours, she continued to do well with no tachypnea and normal glucose levels, however she was very slow feeding and breast milk supplementation was continued after every feeding as she also had a 3% weight loss. Her repeated screening laboratories were normal with no increase in her white blood cell count, left shift or C-reactive protein elevation. Her hematocrit stabilized at 61% and a hemoglobin of 21.2 gm/dL. Blood cultures were negative after 48 hours and the antibiotics were discontinued. She had poor oral intake that required supplementation as she had a maximum weight loss of 8%. After 6 days she was able to stabilize her weight and be discharged with close followup. The patient’s clinical course at 42 weeks corrected gestational age, revealed her weight at 2847 grams which was still below the 3rd percentile but was increasing.
Polycythemia is defined as a venous hematocrit of > 65% or a venous hemoglobin of > 22 g/dL. Capillary values are unreliable and any values greater than normal should be repeated with a venous sampling for confirmation. Hyperviscosity is distinct from polycythemia and “… is defined as a viscosity greater than 14.6 cP at a shear rate of 11.5 per second, or a value 2 standard deviations above the mean.” Hyperviscosity is difficult to measure in the clinical setting therefore polycythemia is often used as a proxy.
Polycythemia occurs in about ~1.5-5% of births. Risk factors for it includes infants that are small for gestation age (SGA, A review is here) and large for gestation age (LGA, A review is here ), infants of diabetic mothers (IDM, a review is here), monochorionic twins (larger twin is more at risk, A review is here), and infants with growth retardation features. Infants born at high altitudes can have polycythemia (a review is here). Polycythemia is less likely in infants < 34 weeks gestation. Other potential risks for polycythemia include acute and chronic hypoxia (e.g. placental insufficiency, preeclampsia, maternal smoking, neonatal thyrotoxicosis), intrauterine transfusion (e.g. materno-fetal, feto-feto) and genetic syndromes such as trisomy 13, 18 and 21 and Beckwith-Weidemann syndrome.
After birth, fluid moves out of the intravascular space and causes the hematocrit to peak at ~ 2 hours of age and decreases around 6 hours of life, with stabilization around 12-24 hours. Factors that influence hematocrit include altitude, postnatal age, fetal hypoxia, intrauterine growth, timing of cord clamping, relative infant and placental height at cord clamping time, and sampling site. Factors that affect viscosity include blood vessel size, hematocrit, deformity of red blood cells, white blood cell concentration, and blood pH.
After confirmation of the polycythemia by venous sampling, dehydration as a cause must be excluded and/or treated. Additionally hypoglycemia and/or other metabolic problems should also be evaluated. Patients who are symptomatic because of polycythemia are treated with partial exchange transfusion where part of the blood volume is replaced with fluids to decrease the hematocrit to try to achieve a lower hematocrit. Treatment of asymptomatic patients is more controversial. For patients with a high hematocrit (~>75%) partial exchange transfusion is usually used. For those that have a hematocrit 70-75% hydration may or may not be used. For those with a hematocrit 65-70% they are usually actively monitored, while some clinicians may also give additional fluid. In 2016, a small (N=55) but prospective study of infants 34 weeks or more gestation, with asymptomatic polycythemia with hematocrit 65-75% found normal saline supplementation did not reduce the need for partial exchange transfusion.
In 2017 a systematic review of delayed vs early umbilical cord clamping for preterm infants found that delayed cord clamping reduced hospital mortality and had “…no major differences in major neonatal morbidities…” such as intraventricular hemorrhage, mechanical ventilation, sepsis, and necrotizing enterocolitis. It also reduced the need for later blood transfusions. Delayed cord clamping also increased the peak hematocrit and the polycythemia incidence. It did not have any impact on use of partial exchange transfusion.
Clinical symptoms associated with polycythemia include:
- Echocardiographic changes – decreased cardiac output, increased pulmonary resistance
- Vascular problems – priapism, testicular infarction
- Poor suck
- Abdominal distention
- Necrotizing enterocolitis
- Abnormal blood smear
- Lethargy/poor feeding
- EEG abnormalities
- Lower intelligence quotient scores
- Motor deficits
- Hypertension, transient
- Renal vein thrombosis
- Respiratory distress
Questions for Further Discussion
1. What are indications for an exchange transfusion?
2. What are potential risks of partial exchange or exchange transfusion?
3. What are causes of anemia in different age groups?
- Disease: Polycythemia | Blood and Blood Disorders
- Symptom/Presentation: Abnormal Laboratory Test | Respiratory Distress
- Specialty: Hematology | Neonatology
- Age: Premature Newborn
To Learn More
To view pediatric review articles on this topic from the past year check PubMed.
Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.
Information prescriptions for patients can be found at MedlinePlus for this topic: Blood Disorders
To view current news articles on this topic check Google News.
To view images related to this topic check Google Images.
To view videos related to this topic check YouTube Videos.
Rosenkrantz TS. Polycythemia and hyperviscosity in the newborn. Semin Thromb Hemost. 2003 Oct;29(5):515-27.
Sankar MJ, Agarwal R, Deorari A, Paul VK. Management of polycythemia in neonates. Indian J Pediatr. 2010 Oct;77(10):1117-21.
Sundaram M, Dutta S, Narang A. Fluid Supplementation versus No Fluid Supplementation in Late Preterm and Term Neonates with Asymptomatic Polycythemia: A Randomized Controlled Trial. Indian Pediatr. 2016 Nov 15;53(11):983-986.
Fogarty M, Osborn DA, Askie L, Seidler AL, Hunter K, Lui K, Simes J, Tarnow-Mordi W. Delayed vs early umbilical cord clamping for preterm infants: a systematic review and meta-analysis. Am J Obstet Gynecol. 2018 Jan;218(1):1-18.
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa