DISCUSSION
Babies are born with small heads for a variety of reasons . A head size less than the third percentile is always troublesome as it may portend smaller brain size , with the potential for long-term neurodevelopmental problems . From our data , over 50 % of these infants had small heads that may be related to fetal exposures that could be toxic to a developing fetus . Unlike previous reports , 7 , 8 our results suggest opioids alone may not be the sole factor , but rather multiple exposures may play an important role in poor head growth in-utero . Tobacco exposure is a common thread for these findings . From the 2016 natality data file of the National Vital Statistics System , the CDC reports the prevalence of maternal smoking at any time during pregnancy to be 7.2 %. 13 Opioid and tobacco exposure were lower than what has been previously reported for WV . 5 This may be a function of a higher socioeconomic status in north central WV , compared to that of the southern and eastern parts of the state , where these exposures are likely much more prevalent . North central West Virginia enjoys a higher socioeconomic climate with lower unemployment , higher standard of living , and higher educational levels , 14 all of which may account for this difference . Regarding opioids , the majority of the mothers were in opioid addiction programs ( buprenorphine and buprenorphine / naloxone , rarely methadone ). In the period reviewed , 11 % of our mothers were smoking during pregnancy , higher than national averages , but lower than the rate reported for WV at 23.8 %. 5
A limitation of this study is the retrospective nature of the data collection . Additionally , dependence on various observers measuring HC without a dedicated team to decrease variability may have led to missing some cases coded as normal and could contribute to data errors . Having a single neonatologist review all births provides some assurance of accurate data recording . Also , we cannot comment on socioeconomic factors that may play a role both in ongoing substance use and general prenatal / perinatal health of the mother that may specifically impact brain growth .
Our primary goal was to determine the contribution of antenatal substance exposure , including opioids , cannabis , and tobacco , to congenital microcephaly . We chose to look at all infants with microcephaly and looked at the prevalence of substance exposure with opioids , cannabis , and tobacco .
While only opioids appeared to contribute to small head size ( less than the 10thth percentile ) in the TN studies , 7 , 8 in our population there appeared to be a stronger association of tobacco use with a HC of less than the third percentile . Of note , in both reports from the TN group the rate of tobacco exposure was very high . They reported 73.2 % of mothers of NAS infants and 51 % of control infants ’ mothers smoked cigarettes . Notably , the TN researchers report a rate of smoking in pregnant women that is much higher than the 12.2 % reported for TN by America ’ s Health Rankings . 5 Perhaps the population studied and reported by the researchers in TN was unique and not repre-
West Virginia Medical Journal • December 2022 • 35