In which trimester of pregnancy is the fetus the most vulnerable to teratogens?

Major malformations are more common in early embryos than in newborns; however, most severely affected embryos are spontaneously aborted during the first six to eight weeks of gestation. During organogenesis between days 15 to 60, teratogenic agents are more likely to cause major congenital malformations.

Which stage of pregnancy is most susceptible to teratogens?

The embryonic period, during which organogenesis takes place, occurs between implantation at around 14 days to around 60 days postconception. This is usually the most sensitive period to teratogenesis when exposure to a teratogenic agent has the greatest likelihood of producing a malformation.

Which stage of pregnancy is least susceptible to teratogens?

The foetal period

The foetus is less vulnerable to teratogens, but as many substances are able to cross the placental blood-barrier it is important to check with your doctor or midwife before taking any medication.

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When should a pregnant mother avoid teratogens?

Talk to your doctor if you’re concerned about being exposed to a particular medication, chemical, or infection during pregnancy. Researchers believe a teratogen can affect a developing fetus about 10 to14 days after conception.

During which trimester is the unborn human organism most vulnerable to developmental defects?

The first trimester of pregnancy is defined as up to the 14th week of pregnancy (13 weeks and 6 days) counting since the first day of your last menstrual period. Harmful exposures during the first trimester have the greatest risk of causing major birth defects.

What are the two most dangerous and most common teratogens?

Perhaps the two most important teratogens today are alcohol and smoking. They are among the leading preventable causes of birth defects and developmental disabilities.

How can teratogens be avoided during pregnancy?

Do not use chemicals that may harm your child – This includes pesticides, fungicides, rodenticides, or harsh cleaning products. Do not smoke, use drugs or consume alcohol during pregnancy – These teratogens greatly increase the risk of fetal birth defects and other life threatening conditions.

What week is most critical in pregnancy?

Pregnancy the three trimesters

  • First Trimester (0 to 13 Weeks) The first trimester is the most crucial to your baby’s development. …
  • Second Trimester (14 to 26 Weeks) The second trimester of pregnancy is often called the “golden period” because many of the unpleasant effects of early pregnancy disappear. …
  • Third Trimester (27 to 40 Weeks)

Is caffeine a teratogen?

In humans, caffeine does not present any teratogenic risk. The increased risk of the most common congenital malformations entailed by moderate consumption of caffeine is very slight.

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How do teratogens affect pregnancy?

As a baby grows in the womb, teratogens may affect parts of the baby’s body as they are forming. For example, the neural tube closes in the first 3 to 5 weeks of the pregnancy. During this time, teratogens can cause neural tube defects such as spina bifida.

What teratogens cause birth defects?

Important teratogens include:

  • Maternal infections: Rubella virus. Cytomegalovirus (CMV). …
  • Maternal illnesses: Diabetes mellitus. Epilepsy.
  • Radiation in very large doses: Excessive amounts of X-ray. Nuclear radiation (e.g. Chernobyl).
  • Drugs: Alcohol. …
  • Environmental pollutants: Methyl mercury.

Which is a best practice for a healthy pregnancy?

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  • Take a prenatal vitamin.
  • Exercise regularly.
  • Write a birth plan.
  • Educate yourself.
  • Change your chores (avoid harsh or toxic cleaners, heavy lifting)
  • Track your weight gain (normal weight gain is 25-35 pounds)
  • Get comfortable shoes.
  • Eat folate-rich foods (lentils, asparagus, oranges, fortified cereals)

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What is the most common teratogen?

The tranquilizer thalidomide is one of the most famous and notorious teratogens. This hypnotic agent was used widely in Europe in 1959, after which an estimated 7000 infants were born with the thalidomide syndrome or meromelia.

Which trimester is most important for brain development?

In the first trimester, nerve connections are built that enable your baby to move around in the womb, while in the second trimester, more nerve connections and brain tissue are formed. In the third trimester, the cerebral cortex starts to take over from the brain stem, preparing your baby for future learning.

Can birth defects be seen on ultrasound?

Ultrasound can detect some types of physical birth defects. Examples of physical birth defects that may be found at 19 – 20 weeks are most cases of spina bifida, some serious heart defects, some kidney problems, absence of part of a limb and some cases of cleft palate.

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What are the symptoms of abnormal baby in pregnancy?


  • Rapid heartbeat.
  • Breathing difficulties.
  • Feeding problems (which result in inadequate weight gain)
  • Swelling in the legs, abdomen, or about the eyes.
  • Pale grey or bluish skin.