Factors Affecting Fetus Development

Bartender serving a cocktail to a young woman
Drinking alcohol during pregnancy can cause problems for the fetus. (Image: XiXinXing/XiXinXing/Getty Images)

The placenta attaches a fetus to a woman's uterine wall, bringing maternal blood vessels close to fetal vessels. Important nutrients and other positive factors pass from the mother's blood into the fetal blood, helping support fetal growth and development. Although the placenta also contains a special protective filter, or barrier, some potentially negative factors can pass from maternal into fetal blood, possibly harming the fetus. If you're pregnant or thinking of becoming pregnant, talk to your doctor about how best to protect your fetus and help ensure a healthy newborn.

Mother's Nutrition

Maternal blood carries glucose that crosses the placenta, providing energy for fetal metabolism. It also contains amino acids, which also cross the placenta and help produce proteins needed for fetal development. Finally, factors called "growth factors" also cross from the mother's blood into fetal blood; they help support development of many different fetal tissues. (ref3p2)

If a pregnant woman becomes malnourished, the fetus might not get sufficient nutrients or other factors, slowing its growth and possibly resulting in an underdeveloped newborn. (ref1p98) If maternal blood glucose is too high, the mother might develop gestational diabetes, which could cause the baby to be too large and have a difficult birth. (ref2)

Maternal Age and Health

A mother's age can also affect the fetus, with older women at increased risk of fetal problems. A study in the "Western Journal of Medicine" in November 2000 evaluated fetal loss due to stillbirth, spontaneous abortion or other problems in more than 600,000 Danish women. The authors found increased negative outcomes in women older than 35, with about 1/5th of their pregnancies resulting in loss of the fetus, compared to younger women; this increased to more than half by age 42. (ref9)

Research also indicates that a woman's overall health impacts her pregnancy. For example, a 2013 study in the "Journal of Obstetrics and Gynecology Canada" found that obese women, at higher risk themselves of hypertension and other problems, were also more likely to have babies with low birth weight or metabolic problems, compared to women of average weight. (ref10)

Lifestyle Impact

Alcohol crosses from the mother's blood into the fetal circulation and, according to a study published in November 2005 in "Obstetrics and Gynecology," one in five pregnant American women indulge in binge drinking. (ref5) Drinking any alcohol during pregnancy can put the fetus at risk of problems called "Fetal Alcohol Spectrum Disorders," which can be moderate to severe. The negative impact on the fetus can include (ref6) poor growth, weak muscle tone, slow development of speech, or heart or facial malformation. (ref4)

Factors in cigarette smoke can also pass into fetal blood, causing potentially serious problems. Nicotine narrows blood vessels, slowing movement of oxygen and nutrients to fetal cells; along with other chemicals in smoke, it might cause low birth weight and increased risk of asthma, gastrointestinal problems or obesity in newborns. (ref7) A study published in February 2008 in "Nicotine and Tobacco Research" found that factors from smoke can also raise the risk of spontaneous abortion or premature birth, and might also cause fetal neurological problems. (ref8)

Some Medications

Some prescription drugs that can cross the placenta might also have negative effects on the fetus. These include the antibiotic tetracycline, which can damage developing teeth, some blood-thinners that can slow nervous system development, and chemotherapy drugs. (ref1p145-6) Illegal drugs such as heroin are especially damaging during the early stages of pregnancy, but might also harm the fetus later in development, slowing fetal growth and causing premature birth or, in rare cases, fetal death. (ref5)

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