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Effect on infants from mothers' multiple substance use in pregnancy – SA study

Substance use during pregnancy is on the increase worldwide and is a significant public health concern, particularly in South Africa, where use of multiple substances during pregnancy is common. The associations are seen in various poorer neonatal outcomes, like decreased birthweight, preterm births, behavioural problems and respiratory issues.

In a survey of 5,232 pregnant women visiting midwife obstetric units in Cape Town, it was found that 36.9% used alcohol and drugs, 34.9% alcohol only, and 1.6% drugs only. Also in Cape Town, a sub-study of the Safe Passage Study (SPS) of the PASS (Prenatal Alcohol in Sudden Infant Death Syndrome and Stillbirth) Network, on the value of maternal serum alpha-fetoprotein measurements, found that 61% of pregnant women smoked, 55% drank alcohol, and 9% and 5% used marijuana and methamphetamine, respectively.

Methamphetamine use in pregnancy is associated with poorer neonatal outcomes, especially decreased birthweight, head circumference and body length. The effects of marijuana use during pregnancy are less clear, with reports ranging from no adverse effect with regard to the likelihood of prematurity or low birthweight (LBW) to a reduction in birthweight, length and head circumference (3) and an increase in preterm births and growth restriction (GR).

The association of marijuana use with poor perinatal outcome seems to be attributable to concomitant use of tobacco and other confounding factors. Perinatal outcome is particularly susceptible to socioeconomic conditions affecting lifestyle choices and behaviour.

Low socioeconomic status and lower educational attainment increase the risk of smoking during pregnancy significantly. Smoking is not only associated with complications such as preterm birth, GR and stillbirth, but has long-term maternal implications such as lung cancer, cardiovascular and chronic respiratory disease, oral diseases and strokes, and long-term infant implications such as respiratory problems (e.g. childhood asthma), infections, obesity, cleft lip/palate, and neurodevelopmental and behavioural problems.

Interestingly, only the effect of cocaine on birthweight remained significant after adjusting for confounding variables. It is important to note that very few pregnant women use methamphetamine or marijuana on their own; most of them also use nicotine or alcohol, or both, reported the research team from Stellenbosch University in the South African Medical Journal.

In a study of 12, 069 pregnant women, they found that 45% of marijuana users also smoked. The same applied to users of methamphetamine, of whom 78.6%, 42.9% and 39.3% used tobacco, alcohol and marijuana, respectively. Of all three health-compromising behaviours, smoking, alcohol consumption and recreational drug use, cigarette smoking has been most studied and strongly implicated in reduced foetal growth.

Their previous finding that significantly more pregnant smokers than pregnant non-smokers engaged in heavy alcohol consumption is supported by Okah et al who found that pregnant smokers were seven times more likely than non-smokers to use alcohol and/or drugs, and that the rate of heavy smoking and moderate/heavy drinking increased with the number of health-compromising behaviours.

Infants antenatally exposed to both alcohol and cigarettes had a substantially higher risk of sudden infant death syndrome compared with those who were unexposed, or exposed to alcohol or cigarettes alone.

As the information on smoking, drinking and drug use for the SPS was collected prospectively, this database was ideal to examine the interactions of substance use during pregnancy on infant outcome.

Study details
The tragedy of smoking, alcohol, and multiple substance use during pregnancy

LT Brink, PE Springer, DG Nel, MD Potter, H Odendaal.

Published in South African Medical Journal on 2 August 2022


Antenatal substance use is a significant public health concern in South Africa. Information on smoking, drinking and drug use during pregnancy was collected prospectively for the Safe Passage Study of the PASS (Prenatal Alcohol in Sudden infant death syndrome and Stillbirth) Network.

Data from 4,926 pregnant women in a community near Tygerberg Academic Hospital, Cape Town, were examined to determine whether associations between different substance use groups and postnatal infant outcomes at birth and one year were significant.

Gestational age (GA) was determined by earliest ultrasound. Maternal data were collected at enrolment or first antenatal visit. Substance use data were obtained at up to four occasions. Birthweight data were derived from medical records, and birthweight z-scores (BWZs) were specifically calculated using INTERGROWTH-21st study data. Statistical analyses were done with Statistica version 13.

Women who used more substances enrolled later, were younger, and had smaller mid-upper arm circumferences (MUACs), less education and lower monthly income than women who used no substances (control group). Infants born to women who used more substances had lower GA at delivery, birthweight and BWZ than infants from the control group. At one year, infants born to women who used more substances had a lower weight, shorter length and smaller head circumference. Education was positively associated with all infant outcomes at birth and one year. MUAC was positively associated with infant BWZ, and weight and length at one year. Income was negatively associated with BWZ, but positively associated with all one-year outcomes.

Substance use during pregnancy affects infant outcomes at birth and one year of age. The addictive properties of substance use make cessation difficult, so prevention strategies should be implemented long before pregnancy. Higher maternal education, associated with better infant outcomes at birth and one year and acting as a countermeasure to substance use, is of paramount importance.


SAMA article – The tragedy of smoking, alcohol, and multiple substance use during pregnancy (Republished under Creative Commons Licence)


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