M

son that the fetus becomes. Fetal physiology adapts to starvation to make the most of whatever nutrients are available. Insulin resistance changes to compensate for lack of muscle tissue. Circulatory changes shunt blood to vital organs. Starvation also causes stress hormone levels to rise, arteries to stiffen, and too few kidney tubules to form. These changes set the stage for type II diabetes mellitus, hypertension, stroke, and coronary artery disease. Paradoxically the infant is scrawny, but the child tends to be obese, and difficulty losing weight persists throughout life.

Many epidemiological investigations have linked IUGR to these conditions. One study of individuals who were fetuses during a seven-month famine in the Netherlands in 1943 documented increased incidence of spontaneous abortion, low birth weight, short stature, and delayed sexual development. Fifty years later, inability to maintain glucose homeostasis was common among these people. Other investigations on older individuals suggest that the conditions associated with what is being called "small baby syndrome" typically manifest after age 65. Experiments on pregnant rats and sheep replicate the spectrum of disorders linked to IUGR, and also indicate that somatostatin and glu-cocorticoid levels change with starvation in the uterus.

Occupational Hazards

Some teratogens are encountered in the workplace. Increased rates of spontaneous abortion and birth defects have been noted among women who work with textile dyes, lead, certain photographic chemicals, semiconductor materials, mercury, and cadmium. We do not know much about the role of the male in environmentally caused birth defects. Men whose jobs expose them to sustained heat, such as smelter workers, glass manufacturers, and bakers, may produce sperm that can fertilize an egg and possibly lead to spontaneous abortion or a birth defect. A virus or a toxic chemical carried in semen may also cause a birth defect. ■

Small head circumference

Low nasal bridge Eye folds

Short nose Small midface

Thin upper lip

Small head circumference

Low nasal bridge Eye folds

Short nose Small midface

Thin upper lip

Figure 23B

Figure 23B

Fetal alcohol syndrome. Some children whose mothers drank alcohol during pregnancy have characteristic flat faces (a) that are strikingly similar in children of different races (b-d). Women who drink excessively while pregnant have a 30% to 45% chance of having a child who is affected to some degree by prenatal exposure to alcohol. Two mixed drinks per day seems to be the level above which damage is likely to occur.

Genital tubercle Urogenital fold

Labioscrotal fold

Labioscrotal Embryonic tail iolds

Genital tubercle

Urogenital folds

Labioscrotal Embryonic tail iolds

Developing penis

Developing penis

Glans penis

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

Get My Free Ebook


Post a comment