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INFECTIOUS
DISEASES

We present two neonates who were born with head circumference centile), at day 50 was 37 cm (60th percentile), and at day 63 was 38
(HC) at or below the 3rd percentile for gestational age and had im- cm (66th percentile), increasing parallel to body growth.
proving head measurements at discharge from the nursery.
Discussion
Case 1: A symmetrically growth-restricted, small for gestational Accurate assessment of the fetal and neonatal head size and
age singleton female infant was born vaginally at 38 weeks and 3 days growth is essential for the diagnosis of microcephaly or of head
of gestation to a Hispanic mother who had traveled to El Salvador growth restriction. A rapid growth phase is expected in the last half
during her fourth month of pregnancy. Prenatal sonography at 13 of the pregnancy, in the absence of nutritional, medical, economic,
weeks and 4 days demonstrated an embryonic crown-rump length or care-related constraints. Early growth patterns of term infants
at 27 percent for age and was otherwise unremarkable. Prenatal are similar across human populations. Preterm growth generally fol-
sonography at 21 weeks and 2 days of gestation demonstrated a fetal lows intrauterine growth rates and shows a unique acceleration dur-
HC at 39 percent for age, a fetal weight at 37 percent for age, and ing the weeks before birth.
was otherwise unremarkable. The birth weight was 2206 grams (0.6th The Society for Maternal-Fetal Medicine recently published the
percentile) and the HC was 29 cm (0.2nd percentile). The forehead criteria and standard reference for diagnosing fetal microcephaly,
was flattened, and cranial molding was present. The infant was hos- when the HC by prenatal ultrasound is 3 standard deviations or
pitalized for 3 days because of microcephaly. Cytomegalovirus more below the mean for gestational age. Preterm and term new-
(CMV), toxoplasmosis, and rubella serologic studies were negative. born growth standards obtained from population-based studies
A brain magnetic resonance imaging showed flattening of the frontal were most recently revised by Fenton and Kim in 2013 and by the
bone. Maternal Zika immunoglobulin M enzyme-linked immunoas- International Fetal and Newborn Growth Consortium for the 21st
say was negative. Neonatal serum real-time reverse transcription century (INTERGROWTH-21st) in 2015. The US National Birth
polymerase chain reaction was negative for ZIKV, dengue, and Defects Prevention Network published prevalence estimates for mi-
chikungunya viruses. During the hospitalization, the HC increased crocephaly from 30 participating births defects databases for the
to 31 cm (1st percentile) by the third day of life. The patient was dis- period 2009 to 2013, studying more than 11 million live births. They
charged with a diagnosis of frontal bone flattening and resolving described a pooled prevalence for microcephaly of 8.7 cases per
congenital cranial molding. Her HC at 14 days of life was 32 cm (2nd 10,000 live-born babies. Prevalence of microcephaly was higher
percentile) and at 39 days of life was 36 cm (35th percentile). among newborns of Hispanics, mothers younger than 20 years,
mothers older than 40 years, preterm babies, low-birth-weight ba-
Case 2: A singleton male infant was born vaginally at 36 weeks bies, and multiple pregnancies. Though specific prevalence data for
and 1 day of gestation to a Hispanic teenager with limited prenatal cranial molding and craniofacial asymmetries were not reported,
care. The mother reported no history of exposure to ZIKV. Pre- molding was recognized as a factor complicating the accuracy of
natal sonography at 23 weeks and 2 days of gestation demonstrated diagnosing microcephaly. The authors acknowledged finding varia-
a fetal HC at 53 percent for age, a fetal weight at 50 percent for age, tion of the definition of microcephaly across the databases, with
and was otherwise unremarkable. The birth weight was 2600 grams common cut-offs for the HC at lower than the 3rd, 5th, or 10th
(35th percentile), the HC was 30 cm (3rd percentile), and molding percentile for age. In our practice, we define microcephaly as a HC
was present. The infant was hospitalized for prematurity, respiratory smaller than the 3rd percentile for gestational age, according to the
distress, head growth restriction, and feeding difficulties. Serologic 2013 Fenton growth charts for neonates. Due to the known risk for
studies CMV, toxoplasmosis, and rubella were negative. A neonatal neurodevelopmental delays among infants with asymmetric head
brain ultrasound and magnetic resonance imaging were unremark- growth restriction, we also offer comprehensive evaluation of new-
able. Maternal and neonatal ZIKV testing were declined by the local borns who have HC measurements significantly smaller than their
Department of Health due to lack of maternal exposure to ZIKV. weight measurement, as had our second patient.
During the birth hospitalization, the HC increased to 32.5cm (27th Infections of CMV, toxoplasmosis, and rubella during pregnancy
percentile) by the seventh day of life. The patient was discharged can cause fetal and neonatal microcephaly. Suspicion of an epidemi-
home on the 11th day of life with a diagnosis of improving con- ologic link between ZIKV maternal infection and fetal embryopathy
genital cranial molding. His HC at day 13 was 33 cm (26th per- occurred in 2015 during the ZIKV epidemic in Central and South
continued on page 20
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