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 Most people know that heavy drinking of alcohol, smoking marijuana, cigarette smoking, and using methamphetamine during pregnancy should be avoided because they can have negative effects on the developing fetus. However, this study found that each of these also had a distinct negative effect on the placenta, suggesting that "different mechanisms mediate their effects on placental development". From Science Daily:

Effects of alcohol, methamphetamine, and marijuana exposure on the placenta

In the United States, prenatal alcohol exposure (PAE) is the most common preventable cause of developmental delay. Animal studies have shown some of the adverse effects of PAE on placental development, but few studies have examined these effects in humans. This is the first study to examine the effects of prenatal exposure to methamphetamine, marijuana, and cigarette smoking on human placental development.

Researchers collected placentas from 103 Cape Coloured (mixed ancestry) pregnant women recruited at their first antenatal clinic visit in Cape Town, South Africa. Of these, 66 heavy drinkers and 37 non-drinkers were interviewed about their alcohol, cigarette smoking, and drug use at three antenatal visits. A senior pathologist, blinded to exposure status, performed comprehensive pathology examinations on each placenta using a standardized protocol. In multivariable regression models, effects of prenatal exposure were examined on placental size, structure, and presence of infections and meconium.

Results show that alcohol, methamphetamine, and marijuana were associated with distinct patterns of pathology, suggesting that different mechanisms mediate their effects on placental development. Alcohol exposure was related to decreased placental weight and a smaller placenta-to-birth weight ratio. By contrast, methamphetamine was associated with larger placental weight and a larger placenta-to-birth weight ratio. Marijuana was also associated with larger placental weight. In addition, alcohol exposure was associated with an increased risk of placental hemorrhage. Finally, alcohol and cigarette smoking were associated with a decreased risk of intrauterine passing of meconium, a sign of acute fetal stress and/or hypoxia; methamphetamine, with an increased risk. These findings may be important in the long-term teratogenic effects of prenatal alcohol and drug exposure.

Some recent research on sperm quality and implications for fertility. All from Science Daily:

Exposure to aluminum may impact on male fertility, research suggests

Research from scientists in the UK and France suggests that human exposure to aluminum may be a significant factor in falling sperm counts and reduced male fertility.Fluorescence microscopy using an aluminum-specific stain confirmed the presence of aluminum in semen and showed aluminum inside individual sperm.And the team of scientists, at the universities of Lyon and Saint-Etienne in France and Keele in the UK, found that the higher the aluminum, the lower sperm count.

Professor Exley said: "There has been a significant decline in male fertility, including sperm count, throughout the developed world over the past several decades and previous research has linked this to environmental factors such as endocrine disruptors"..."Human exposure to aluminum has increased significantly over the same time period and our observation of significant contamination of male semen by aluminum must implicate aluminum as a potential contributor to these changes in reproductive fertility."

Stress degrades sperm quality, study shows

Psychological stress is harmful to sperm and semen quality, affecting its concentration, appearance, and ability to fertilize an egg, according to a study. It is not fully understood how stress affects semen quality. It may trigger the release of steroid hormones called glucocorticoids, which in turn could blunt levels of testosterone and sperm production. Another possibility is oxidative stress, which has been shown to affect semen quality and fertility.

Twenty hours of TV a week linked to almost half sperm count of those who watch little TV

Healthy young men who watch TV for more than 20 hours a week have almost half the sperm count of men who watch very little TV, indicates a new study.

Cell phones negatively affect male fertility, new study suggests

Men who keep a cell phone in their pant pocket could be inadvertently damaging their chances of becoming a father, according to a new study. Previous research has suggested that radio-frequency electromagnetic radiation (RF-EMR) emitted by the devices can have a detrimental effect on male fertility. Most of the global adult population own mobile phones, and around 14% of couples in high and middle income countries have difficulty conceiving.

In control groups, 50-85% of sperm have normal movement. The researchers found this proportion fell by an average of 8 percentage points when there was exposure to mobile phones. Similar effects were seen for sperm viability. The effects on sperm concentration were less clear. 

Moderate weekly alcohol intake linked to poorer sperm quality in healthy young men

Moderate alcohol intake of at least 5 units every week is linked to poorer sperm quality in otherwise healthy young men, suggests research. And the higher the weekly tally of units, the worse the sperm quality seems to be, the findings indicate, prompting the researchers to suggest that young men should be advised to steer clear of habitual drinking.

Sperm size, shape in young men affected by cannabis use

Young men who use cannabis may be putting their fertility at risk by inadvertently affecting the size and shape of their sperm, according to new research. In the world's largest study to investigate how common lifestyle factors influence the size and shape of sperm, a research team found that sperm size and shape was worse in samples ejaculated in the summer months, but was better in men who had abstained from sexual activity for more than six days.