Pregnant? Need Help?

Pregnancy Options Workbook

9. Fetal Development

Many people need to know about stages of pregnancy and development of the pregnancy before they can make their decision. Or, you might just be curious to know how a sperm and an egg end up as a baby!

"How big is it? Is it formed?"

Doctors date the pregnancy from your last menstrual period (LMP), which is the beginning of your cycle. Most conceptions happen two weeks after your last period. The following descriptions are based on the actual age of the embryo or fetus. This is usually two weeks less than age by LMP. (The LMP age is also listed.)
Example: If your last period was 8 weeks ago, the embryo is 6 weeks old.
But your doctor will consider you 8 weeks along, because your cycle started then.

How pregnant are you?

First Day of Your Last Menstrual Period?_______________________

Today's date______________________

How many weeks between these two dates? __________

The growing embryo or fetus is two weeks less. It is now_______________
weeks old. This is called the gestational age.
(Number of weeks since period - 2= gestational age)

Conception

Conception begins when the egg and sperm meet at the top of the fallopian tube after intercourse. After the egg and sperm fuse and become one, the new cell begins to divide. The cells divide and form two joined cells. These two cells divide again and again. By the time the conception reaches the uterus it is now made up of 8 - 12 cells. This ball of cells drops into the uterus and begins to find a spot along the wall of the uterus. This takes 5 days from conception.

Implantation

Over the next 10 days, the ball of cells begins to bury itself into the top layer of the lining of the uterus. Some of the cells have the job to bury into the uterus and other cells begin to work together to start forming an embryo. Growth happens when cells divide. The embryo grows into a fetus.

The sex was decided when the sperm fertilized the egg. There are two kinds of sperm, "X" bearing sperm and "Y" bearing sperm. Sex is determined by type of sperm. If fertilization happened with an "X" sperm then the fetus will be female. If it involved a "Y" sperm then the fetus will be male.

Development

Weeks 2-4 (4-6 LMP)
The embryo begins to take shape. It goes from looking like a ball of cells to the shape of a small summer squash. By the third week, the squash shaped embryo grows a ridge that goes almost all around. Over the next 8 weeks, the ridge will grow and begin to form the spine and the early brain. In the fourth week, a very small tube is formed inside of this squash shaped embryo. This tube is the first step to many, many more steps that forms a heart. The embryo is the size of a poppy seed.

Week 5-6 (7-8 LMP)
The embryo will grow from the size of an apple seed to the size of a blueberry in these two weeks. The embryo begins to bathe in clear liquid. The fetus begins to form limb "buds." which, over the next 4 weeks, grow into arms and legs.

Week 7-8 (9-10 LMP)
The fetus will first be as big a raspberry and eventually become the size of a small grape. In this two week period the part of the fetus that will eventually be the face begins to form the shape of eyes and ears. The fetal heart has grown from a tube to a four chambered heart. The liver, kidneys and pancreas have begun to form.

Week 9-10 (11-12 LMP)
During this time the fetus grows to the size of an average strawberry. The eyes, ears, nose and mouth continue to form. The soft skeleton is forming and muscle tissue begins to collect around it.

Week 11-12 (13-14 LMP)
By the 12th week, the fetus has grown to the size of lime. The skeleton begins to harden. Blood vessels form in various parts of the fetus and begin to connect to one another.

4th month: 13-16 weeks (15-18 LMP)
By the end of this month (16 weeks) the fetus will measure about 10 centimeters, or about 4 1/2 inches. The stomach, intestine and colon have formed. The four chambered heart begins to build up muscle cells. Blood cells formed in the bone marrow begin to collect in the vessels. The skin covering the body begins to thicken and hair appears. The inner ear forms. The kidneys are formed and working. The ovary, uterus, vagina or penis have been forming over the last couple of weeks.

5th month: 17-20 weeks (19-22 LMP)
By the end of this month the fetus will be at least 12 inches long. The nose takes a more defined shape as cartilage (the soft bone) appears.

6th month: 21-24 weeks (23-26 LMP)
During the sixth month fetus weighs about 2 lb. and is 14 inches long. At this stage of development the various organs have formed. The following months will see increase in body fat.

7th month - 9th month
Over the next three months the fetus will gain at least five pounds and grow another 6- 7 inches. In the eighth month, taste buds form in the mouth. the
lungs continue to make many small pockets to allow for breathing after birth.

What can hurt the pregnancy?

Birth Defects

Birth defects can happen for many reasons. Each pregnancy carries a 2-3 % chance that the child will be born with a physical deformity and/or have some degree of mental retardation. The causes of birth defects can include
1. inherited conditions that are passed down in families,
2. accidental changes to the genes at the time the egg or sperm were forming, and
3. exposures to some kinds of chemicals, diseases, pollutants, and medications, including things you eat, drink and breathe.

If you are worried that your baby may inherit a condition or have been exposed to something bad, discuss this with your doctor. Or, ask to talk to a genetic counselor. Genetic counselors help women and families understand their chance of passing on a known condition in the family.

Do you know of an inherited disease or condition in your family?

Describe it:


Does you or anyone in your family have a birth defect?

Describe it:


Exposures

Some birth defects are caused by drugs, chemicals, viruses and by some medical conditions that a pregnant woman may have. These factors or "teratogens" should be avoided or controlled. If you are wondering if something you were exposed to can harm the pregnancy, keep reading and check the resource section for more help.

Have you been exposed to a chemical, drugs, medications, radiation/ x-rays or viruses since your last period (LMP)? For each item you listed, write down all the days you were exposed and if you know, the dosage. To decide if you may have a risk it is important to know:
How old the embryo/fetus was when the exposure(s) occurred.
What you were exposed to?
How much, and for how long, was the exposure?
Exposure Amount Date Gestational age
(Ex: X-ray of head 3 pictures 4-1 9 weeks)

1.

2.

3.

Use additional paper if you have more to list. Show this to your doctor or genetic counselor.
Was the baby's father exposed to chemicals, drugs, medications, radiation/ x-rays or viruses for the three months before you believe you conceived this pregnancy?
List them:
1.
2.
3.


Some Common Exposures

Here are some common exposures and the level of risk to the developing fetus. This is only a partial list. If your pregnancy has been exposed to one of these, please discuss this with your doctor. Additional information can be obtained (see resource section). Or, call a genetic counseling service at your medical center.

In alphabetical order:

Acne medications (retin A or Accutane):
Several years ago a new drug was made available to treat acne. This drug has also been prescribed for other facial blemishes.
Time of exposure to avoid: The first 12 weeks of pregnancy
Greatest risk: Between the second week and 5th week of pregnancy
Risks: There is a 25% risk that embryo/fetus exposed in the first 12 weeks will have a birth defect affecting the brain, heart and/or face. There is also a greater chance of miscarriage. It is important to remember that once you stop taking this drug it can stay in your body for weeks.

Alcohol:
Time of exposure to avoid: Anytime in pregnancy
Greatest Risk: fetal alcohol syndrome Fetal alcohol syndrome (FAS) is the leading cause of mental retardation in the U.S. Children who have FAS have growth delays, nervousness, possible heart defects as well as learning difficulties. Alcohol crosses the placenta, which means the baby gets it directly. Daily or excessive (over 5 drinks per day) alcohol use can harm the baby. There is no agreement on a safe level of alcohol use in pregnancy. FAS has been known to occur even for women who use alcohol in small amounts.
Uncertain risks: binge drinking or occasional social use. Risk in this situation is dependent on the stage of pregnancy, amount of alcohol and what type of alcoholic beverage was consumed. This is not a risk-free situation. You need to have a medical professional review your exposure. The father's use of alcohol has not been proven to affect the developing fetus or child.

Antibiotics
Some, but not all antibiotics are known to cause birth defects. Check with your doctor to learn if the antibiotic you were given carries a risk of birth defects.
For example, let's look at the risk of taking one antibiotic, streptomycin.
Time of exposure to avoid: The first 12 weeks
Greatest risk: After 4th week of pregnancy
Risks: There is an almost 10% risk that the ears of the developing fetus can be affected and result in deafness.

Anticonvulsants (medications to control seizures):
There are many different kinds of medications for seizure conditions. It is important to learn if the medication you are taking is known to carry a risk.
Time of exposure to avoid: The first and second trimesters (up to 24 weeks)
Greatest risk: The first 12 weeks.
Risks: Depending on which anticonvulsant was used in the pregnancy, there is a risk for heart defects, spina bifida, cleft lip, and mental and physical delays.

Catbox/ toxoplasmosis:
In the U.S. 3000 infants are born with birth defects resulting from exposure in early pregnancy to the parasite, toxoplasma gondii.
Time of exposure to avoid: The first 12 weeks
Risks: About 30% of all women who become infected with this parasite in early pregnancy will pass it to the fetus. If it is exposed during this time, the baby is at risk for brain malformations, deafness, vision abnormalities, and mental retardation.

Cigarette Smoking:
Time of exposure to avoid: The entire pregnancy
Greatest risk: The risk for complication rises with the number of cigarettes smoked per day and how far into the pregnancy the smoking occurred.
Risks: Women who smoke in their pregnancy have an increased chance that the pregnancy will end in a miscarriage or stillbirth. The babies are sometimes born with low birthweights. This is a critical risk for delay in the growth and development of the baby. Women who smoke have a greater risk than women who do not smoke for the baby to die from SIDS (sudden infant death syndrome).

Cocaine use:
Time of exposure to avoid: The entire pregnancy
Risks: Women who use cocaine in their pregnancy are more likely to have premature infants. Birth defects have been reported in exposed fetuses. Brain malformations, deformities of arms and legs, and abnormalities of the intestines have been reported.

Diabetes:
Diabetes can affect anyone at any age. Some forms of diabetes require the person to take insulin. Whether you take insulin or not, there is a known increased risk for birth defects. The medical condition of diabetes exposes the fetus to risk factors. The risk for having a child with a birth defect is about 6-9%.
Greatest risks: Women who take insulin and are not in control of daily insulin levels.
Risks: Many different kinds of birth defects can occur but the most common are spina bifida, heart defects and deformity of the legs. Women who are able to take insulin and control the diabetes have an excellent chance of avoiding this risk.

Medications for depression and anxiety:
There are many different medications that are used to help people with depression and feelings of anxiety or panic. It is important to tell your doctor that you are pregnant. Many of the new medications appear to not carry an increased risk of birth defects. There are some, such as lithium, which appears to bring an increased risk for a specific kind of heart defect. It does not happen to all babies exposed to lithium in pregnancy.

Microwaves/sitting in front of a computer screen
There is no proof that microwaves or using computers puts a pregnancy at risk for birth defects.

Paint (household):
There is no evidence that use of household paint increases the risk of birth defects. Please remember to have good ventilation when painting.

Thyroid medicine:
There are medications that are prescribed for over-active and under-active thyroid. Ask your doctor if the medication you are taking is known to cause birth defects. Usually the time to avoid use of some forms of thyroid medication is between 4-20 weeks of fetal development.
Risks: Most common concern is developing an underactive thyroid in the fetus. Some forms of medication can lead to skin not forming on parts of the body, like the head.

Viruses:
Some examples: Rubella (German measles), chicken pox, cytomegalovirus,
Time of exposure to avoid: The first 12 weeks of pregnancy
Risks: Women who are exposed to one of these virus during the first half of their pregnancy, and who never had been exposed before, may develop the illness. During this time, the embryo or fetus is also exposed. If the viral infection occurs during the development of the early brain, this can result in brain deformity and mental retardation.

Workplace Exposures:
If you work where chemicals are being used, it is your legal right to have full disclosure of what the chemicals are and if they are known to affect health or pregnancies. Once you receive the list you may need to call a genetic counseling service in your city or state to review the documents for you.

X-Rays/radiation:
We have radiation exposure in lots of ways, at work, in our homes (radon) and when we have an X-ray. A critical aspect of x-rays is dosage or amount. Most average exposures are about 1 rad. Concern arises when a pregnancy is exposed to more than 5 rads. This would be the result of an unusual circumstance or medical crisis.
Time of exposure to avoid: The first and second trimester
Greatest risk: Before implantation of the dividing egg, day 1-9.
Risks: There is an increase risk for miscarriage. Exposures after day 9 can result stillbirth, stunted growth, eye problems and a higher risk for mental retardation.

It is important to remember that all pregnancies carry a 2-3% risk of birth defects.

Resources
March of Dimes local office- for information on teratogens and things that will harm a pregnancy.
Genetic Counselor- your local medical center, or call the National Society of Genetic Counselors,




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