83 had head circumferences less than the 10th percentile , but greater than the third percentile and were not included in the analysis . Sixty-five infants , 1.02 % of the newborns from the study period , were identified as having microcephaly .
Of the 65 infants with congenital microcephaly , 32 ( 49.2 %) had no exposures . A detailed review of these charts showed that 11 infants had recognized congenital / genetic abnormalities and 11 infants were growth retarded secondary to maternal hypertension , preeclampsia , or HELLP syndrome , while seven infants may have been adversely affected by maternal infections . Of the infants , two of the mothers had a history of chlamydia , one in the past and one in the first trimester , and two were Group B Streptococcus ( GBS ) positive with one being HSV1 positive with positive IgG for Parvovirus B19 . Another mother was positive for HSV1 and 2 IgM . Two of the microcephalic infants with no exposures were born to a mother who was positive for Toxoplasma and one who was positive for CMV IgG , but the infant ’ s CMV PCR was negative . The mother with Toxoplasma also used Wellbutrin during pregnancy . Three mothers had alcohol exposure during pregnancy , but one also had hypertension and one had preeclampsia .
The other 33 ( 50.8 %) microcephaly cases had exposures related to fetal exposures ( Table 1 ). All 33 of these infants were exposed to maternal tobacco use , 32 from cigarette smoking and one from an electronic cigarette , representing 4.8 % of the 689 babies born to mothers who smoked cigarettes from our total population of 6,343 infants . Ten infants ( 30 % of microcephalic babies ) had exposure to only tobacco , which represented 1.5 % of the 689 babies born to mothers who smoked cigarettes . A total of 23 ( 69.7 %) of these microcephaly cases were also exposed to maternal opioids , representing 6 % of the 381 babies born to mothers who were on opioids from our total newborn population . Cannabis exposure alone did not seem to be a factor in microcephaly unless its use was accompanied by tobacco and / or opioids . Eleven ( 33.3 %) of the infants with microcephaly also had maternal cannabis use , though these infants ’ mothers also used tobacco . Six ( 18.2 %) of the 11 used cannabis along with tobacco and opioids . Bivariate correlation analyses demonstrated that tobacco , cannabis , and opioid exposure were all significantly correlated negatively with head circumference percentile at birth ( p < 0.001 ). The greater number of substance exposures also correlated negatively with the circumference percentile at birth ( p < 0.02 ). These areas of significance are detailed in Table 1 . Z scores for head circumference ranged from -2.18 to -2.85 . The percentage of babies that were small for gestational age ( SGA ) ranged from 65 % to 100 %. Maternal BMI at the time of delivery ranged from 29.09 ± 6.77 to 31.63 ± 8.42 . For all of these measures , the trends were lower head circumference Z scores , greater percentage of babies born SGA , and lower maternal BMI with the combined prenatal exposures of tobacco , cannabis , and opioids , though these trends were not statistically different .
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