Study: Prenatal tobacco, marijuana use can affect infant size, behavior

Prenatal exposure to tobacco and marijuana can affect infant size and behavior, according to a study published in Child Development. Infants who were exposed to both substances, especially during the third trimester, were smaller in length, weight, and head size, in addition to a greater likelihood of being born early, compared to infants who were not exposed to the two substances.

The study included a sample of 247 mother-infant dyads. Of these, 173 had either been exposed to just tobacco or a combination of tobacco and marijuana. The mothers in the study ranged in age from 19 to 40 (M=25.39). Maternal race was 52% African American, 30% Caucasian, and 8% other or mixed race. Approximately 44% of the mothers were married or living with their partner, 35% were in a relationship but not cohabiting, and 21% were single. Approximately 26% of the mothers had less than a high school education, 60% completed high school, 10% completed some college courses, and 4% had a vocational degree or technical training degree.

Maternal smoking status was determined through a combination of self-report and maternal saliva samples collected once per trimester. Saliva was tested by the US Drug Testing Laboratory for ∆⁹-tetrahydrocannabinol (THC), the psychoactive component of marijuana. After the infant’s birth, meconium specimens were collected from soiled diapers twice daily until the appearance of milk stool, which was tested for THC and nicotine.

The researchers found that infants with positive meconium results for both tobacco and marijuana had smaller head circumference (mean difference [M]=32.79 cm, SD=2.06), shorter birth length (M=48.61 cm, SD=3.65), lower gestational age (M=38.36 weeks, SD =2.21) and birth weight (M=2886 g, SD=576.7) compared to infants who had negative meconium results for both substances ([head circumference, M=34.42 cm, SD =1.62], [birth length, M=50.35 cm, SD=1.96], [gestational age, M=39.2 weeks, SD=1.41], [birth weight, M=3340 g, SD=532.8]). Infants who tested positive for only tobacco had smaller head circumferences compared to infants who tested negative for both (M=33.63, SD=1.76).

In addition to testing for prenatal exposure to tobacco and marijuana, the researchers also analyzed maternal anger and prenatal/postnatal stress and infant reactivity and regulation. Symptoms of maternal anger were measured using the Buss-Perry Aggression Questionnaire, which was administered during the third trimester and again when infants reached 2 months. The participants self-reported and the researchers averaged the results from the four measured scales of physical aggression, verbal aggression, anger, and hostility. Higher scores indicated higher anger. Perceived stress was assessed using the Perceived Stress Scale (5-point scale), which was also administered once during the third trimester and once when infants reached 2 months. Again, the participants self-reported and the researchers extrapolated a mean value from the results. Infant reactivity and regulation (Infant RR) was measured at 9 months using the Infant Behavior Questionnaire-Revised as well as behavioral measures through an anger frustration paradigm.

Mothers who were positive for both tobacco and marijuana also reported high aggression in pregnancy and postpartum compared to those who were negative for both. The researchers used the mean scores from the self-reported questionnaires to determine mean values (M) and standard deviation (SD).

For tobacco- and marijuana-positive mothers, mean value recorded for anger during pregnancy was 3.01, SD=0.64 and for stress during pregnancy was 24.88, SD=7.25 versus 24.60, SD-8.15 for mothers not exposed to the two substances. After pregnancy, mothers who tested positive for both substances recorded postnatal mean scores for anger of 2.66, SD=0.74 and postnatal stress of 19.63, SD=7.17. Negative-testing mothers recorded mean values for postnatal anger of 2.31, SD=0.64 and for postnatal stress of 22.21, SD=8.46. While there was no direct significant association between co-exposure to tobacco and marijuana and infant RR, there was an indirect association between the two substances and lower birth weight and size (ß=.05, 95% CI [.01, .10]).

The researchers highlighted a few strengths and limitations of the study. They noted that while accurate assessment of substance use is difficult, they incorporated multiple indices of substance use into the study, including self-reporting, interviews, and maternal saliva and infant meconium samples. They also recognize that the study did not account for maternal psychological symptoms and personality disorders, which have been associated with cigarette smoking. Infant RR was also limited to a single brief task and thus, must be generalized. The researchers believe one of the study’s major strengths was controlling for alcohol exposure. Going forward, the authors said their findings illustrate the need to focus on helping pregnant smokers reduce stress and cope with negative emotions during cessation interventions.

Note from Dr. Lockwood

"We should always be mindful of the potential for reverse causality in such studies. For example, it is possible that anxious people are more likely to smoke cigarettes and marijuana."

Is HT-NIPT cost-effective for guiding postpartum use of anti-D?

A simulation by British investigators shows that high-throughput, noninvasive prenatal testing (HT-NIPT) for fetal Rhesus D (RhD) may help save costs by reducing unnecessary treatment with routine anti-D immunoglobulin. The extent of the savings depends on the overall test cost.

Published in BJOG, the findings are based on use of a decision-tree model to simulate a population of 100,000 RhD-negative women not known to be sensitized to the RhD antigen. The model was used to characterize the antenatal care pathway in England and long-term consequences of sensitization events.

The authors derived the diagnostic accuracy of HT-NIPT from a systematic review and bivariate meta-analysis. Relevant literature sources and databases were used to estimate other inputs. Women in whom HT-NIPT was positive or inconclusive continued to receive routine anti-D immunoglobulin prophylaxis (RAADP); those with a negative HT-NIPT did not receive RAADP.

Five alternative strategies in which use of HT-NIPT might affect the existing postpartum care were considered by the researchers. Costs were in 2015 British Pounds Sterling and impact on health outcomes was expressed in terms of quality-adjusted life-years over a lifetime.

The simulation suggested that HT-NIPT saved costs but was also less effective than current practice, irrespective of the postpartum strategy the authors evaluated. The best performance was with a postpartum strategy in which inconclusive tests results were distinguished from positive results. HT-NIPT was only cost-effective if the overall test cost was no more than £26.60 (approximately $36.96).

Study: Lesbian, bisexual women at greater risk for type 2 diabetes

A study published in Diabetes Care shows that lesbian and bisexual (LB) women have a greater likelihood of developing type 2 diabetes (T2D) than their heterosexual counterparts. The researchers found that stress, along with a higher body mass index (BMI), may be the primary contributing factors to the disparity.

The study included women participating in the Nurses’ Health Study II who were aged 24 to 44 at the start of the study in 1989. The participants were prospectively followed through 2013. Self-reported clinician diagnosis of T2D was assessed every other year to identify incidence. The participants self-reported sexual orientation; 1267 identified as lesbian or bisexual and 92,983 reported as heterosexual.

The researchers found that LB women had a 27% higher risk of developing T2D than heterosexual women (adjusted incidence rate ratio [IRR] 1.27, 95% CI 1.05-1.54). At the end of the study, 6399 women had developed T2D with lesbian and bisexual women having a 22% greater risk of the disease. In addition, differences between LB and heterosexual women in risk of diabetes were greater at younger ages (sexual orientation-by-age interaction, P < 0.001). A higher BMI was an important factor contributing to the identified disparities; the IRR was completely attenuated when BMI was added to the regression model (IRR 0.85, 95% CI 0.70-1.03).

The researchers believe that disparities between LB and heterosexual women may be a result of LB women being more likely to have risk factors such as obesity, tobacco smoking, heavy alcohol drinking, and stress-related exposures. Stress could be related to discrimination, violence, victimization and psychological distress, which were reportedly higher for LB women. The researchers believe that public health and clinical efforts should be made to prevent, detect, and manage obesity and T2D among LB and more research is needed on disease management and on the overall health of lesbian and bisexual women.