What Is Happening When I Am Pregnant?


SexEdNotes   ~   Pregnancy


In these Anatomy sections, new terms or the names of new body parts will have Leading Caps to emphasize to the reader their significance. Be sure you know what each term or part is as you read through the material.


Conception is the very beginning of a new life. But a lot has to happen before this new life can see the light of day.

Some terms we need to know  before we can talk about pregnancy:

Umbilical Cord: About 19 inches long and 3/4 inch wide, it connects from the Placenta inside the woman's uterus to the belly of the Embryo/Fetus. It carries two arteries (which carry fetal blood from the mother's Placenta to the Fetus) and one vein (to return the used fetal blood from the Fetus to the Placenta). All of the blood within the Fetus and the Umbilical Cord belongs to the Fetus. When the child is delivered, the cord is tied in two places, then severed between the ties. Sometimes the blood that remains in the Umbilical Cord may be saved in special blood banks for use later on by the child for stem cell research or special disease and blood work.

Placenta: Also known as the "Afterbirth" (because it is usually delivered after the baby is delivered and then discarded)  is formed when the fertilized Egg attached itself to the inside of the mother's Uterus. It is about 8 inches in diameter and weighs about one pound at delivery. It diffuses oxygen, proteins, and vitamins from the mother's blood and places it in the blood of the Fetus (baby). It keeps the mother's blood and the fetal blood completely separate, and it produces Progesterone of pregnancy, a hormone. After the birth, it is expelled about ten minutes after the birth by the mother, during the third stage (Placental stage) of delivery.

Amniotic Sac: This is what is commonly called the "bag of waters", and it basically is a tough membrane called an Amnion that contains the Fetus, which floats in a clear fluid called Amniotic Fluid. This fluid is mostly water, very similar to sea water, and carries protein. The Amnion gently grows, enlarging the Uterus to provide room for movement of the Fetus as it grows. It contains about 2 1/3 pints @36 weeks and 1 3/4 pints @ 40 weeks, and because the fluid absorbs wastes from the developing fetus, it is completely filtered every 1 to 3 hours by the mother's body. The fluid protects the Fetus from bumps and shocks, and from rapid temperature changes.

Weight Gain:  This should be between 25 and 30 pounds maximum. The Fetus, Placenta, and Amniotic Sac w/fluid averages 10 pounds... the rest of any weight gained by the mother is fatty tissue and fluids in her body. Several pounds of that fatty tissue are increased breast development (in preparation for breastfeeding), so it is 'good' weight. But when we talk about "eating for two", that does not mean to double the intake of food. The average active woman should have 2300 calories of food intake per day. The Fetus only needs 300 calories per day.

Drugs - Alcohol - Tobacco - ANY Drugs!! --- NO!! Doctor prescribed drugs should be ok, but be certain that the doctor is aware that you are pregnant. You will be asked, so be sure to tell the truth, for the Fetus's sake! Many OTC drugs and prescription drugs can cause damage to the Fetus. A well-known example was Thalidomide. It was considered to be a non-addictive tranquilizer/sleeping pill that helped to stop nausea, and was synthesized in West Germany in 1956. The USA would not allow its use, but it was brought in by doctors or mothers that traveled to other countries. Later it was learned that it affected the Fetus. We had 8,000 survivors that were born with Phocomelia, which causes babies to be born with their hands or feet formed at the body, like flippers, along with dwarfism, brain damage, etc.  It was withdrawn from all markets in 1961 but it was still being sold by some countries. It is again being used for non-pregnant cancer patients, but under strict control. An 85-year old male friend had to fill out a paper swearing that he was not pregnant before they would allow him to take the medication. :-)

Another drug is Accutane, which is sold in the US for control of acne, but by prescription only. Teens are susceptible to danger here due to concern about acne and their reluctance to admit that they might or could be pregnant. It causes severe fetal defects, similar to Down's Syndrome

Illness During Pregnancy:  A pregnant woman should report any illness to her doctor. She should avoid any fever, chill, heavy cold, etc. Exposure to Rubella (German Measles) during the 12th week of pregnancy may interrupt development of the Fetus, resulting in deafness or heart defects.

Amniocentesis:  This is the extraction of 10 - 20 ml of Amniotic Fluid from the Amniotic Sac for analysis. It is done between the 12th and 16th week of pregnancy to find possible abnormalities such as Down's Syndrome or Spina Bifida, etc. The test itself can pose a 1/2000 risk to the Fetus, so use good judgment before having the test done.

Ectopic Pregnancy:  The risk of this happening is high if the fertilized Egg takes more than 7 days to reach the Uterus. The Chorionic Villi of the Egg will attach to the inside of the Fallopian Tube, and the Fetus will start developing inside the tube rather than inside the Uterus. If not caught in time it could be fatal to the mother, and it will be fatal to the Fetus because it must be surgically removed. In very rare cases the Fetus may break through the tube and attach somewhere inside the abdomen (but not in the Uterus). In that case it will have to be delivered by Cesarean Section as there is no exit passageway from inside the abdomen.

Sexual Intercourse During Pregnancy:  Always follow the doctor's advice, but normal, gentle sexual activity with the mother "in control" of everything is usually OK, unless:

  • The doctor says "NO"

  • It is uncomfortable for the mother

  • Too much pressure is placed on the outside of the mother's abdomen

  • The Cervical Mucus Plug is gone from the Os due to the mother's Cervix starting to dilate for delivery.

In some cases orgasm (with or without sexual intercourse) has been recommended to exercise the Uterus, as orgasmic contractions are similar to labor contractions. However, it has been known to hasten the labor process if it has begun naturally, so not after the Cervix is dilated.


A Timeline of What Is Happening Both Inside and Outside the Uterus:

BLASTOCYST - EMBRYO - FETUS                                                   MOTHER'S                   .

.              EVENTS                                      WEEK                             EVENTS                    

  0 - First day of last menstruation (When the Egg is released, not when the flow appears)
Conception - 1 - Intercourse (Coitus)
Blastocyst (from one to six days after fertilization)     implants into the Uterine wall.  - 2  
Embryo can be seen by the naked eye - 4 - First missed menstrual period
- Urine test will reveal pregnancy
Spine, nervous system starts to form - 5 - Breasts soften, enlarge
-Veins and milk ducts show on breasts (Pic #2)
- Areolae darken (Pic #3)
Rudimentary heart, circulatory system forms - 6 - Gums soften
- Morning Sickness (eat small, frequent meals)
  7 - Stretch marks may appear on breasts (Pic #4)
All main organs are formed -
Now referred to as a "Fetus" -
Fetus is now 1" long -
8 - Physical signs of pregnancy (enlarged Uterus (womb), soft Cervix, frequent urination)
  9 - Colostrum may now be squeezed from the breast
  10 - Doctor can feel contractions of Womb
  12 -Morning sickness usually stops by this time
Fetus can swallow, urinate, suck its thumb -
Placenta is formed -
  15 - Pigmentation of breasts
- Darker skinned women may show a dark line from navel to pubic hair (Pic #5)
Skeleton forms -
Fetal heartbeat can be heard -
Sex can be distinguished -
Fine hair on skin
16 -Womb visible in abdomen
- Stretch marks may stay
  18 - Movement felt (called Quickening)
Position in Womb changes until the 28th week - 21  
Eyelids open -
Hands able to grip things -
Phallic growth occurs - previously, gender determination difficult by ultrasound -
  24 - Womb may be felt at Navel level
Fetus is 13 inches long - 25  
Chance of survival if born at this point - 28 - Average weight gain 19 pounds
- Average breast weight gain 19 ounces
  30 - Navel flattens out
Fetal position MAY be corrected by manipulation 34  
  35 - Ribs spread to provide more room for lungs
- Nerve pains
- Should curtail traveling
Head drops into mom's pelvic cavity - 36 - Womb moves up to ribs
- Must lean backward to balance (Pic #6)
- Pressure of Fetus's head on bladder causes       . . frequent urination.
Is premature if born before now -
Weighs less than 5 lb - 8 oz -
  39 -
Birth happens -
Average weight 7 1/2 pounds -
40 - Uterus contracts rhythmically - Labor Pains
- Membranes rupture (water breaks)
- Average weight gain 25 to 30 pounds
- During later months may have unusual food cravings, varicose veins

Pregnancy lasts forty weeks, or 9 calendar months, or 9 x 31 = 279 days, or ten lunar months.





PIC #1  Starting from the right side of this image, this image is a composite of images taken of the same woman, every month, as her pregnancy progresses. The obvious change is the increase of the size of her belly as her Fetus develops. Refer back to this image to see other bodily changes that we will discuss.


Referring to the references in the chart above:

PIC #2 shows veining on the breasts. Some breasts will always show some veins. But when a woman is pregnant, she will often see her breast veins appear when they have never been seen before. This is because her breasts are developing beyond the stage they reached when she became an adult and finished puberty. Tanner Breast Development Scale takes the breast development from Stage One to Stage Five. When a woman becomes pregnant, her breasts may be the first indication that she is pregnant. They start developing their Acini tissues to produce milk, and that can almost be referred to as a "Stage Six", which is not an 'official' Tanner stage. 






PIC #3 shows that the Areolae on the breasts will darken, and in some cases they will become wider as well. This is due to an increase in the hormone made by the Placenta which produces a melanocyte-stimulating hormone. This produces more melanin which causes our skin to darken to protect itself from excess sunlight. When an increased amount of that hormone is generated, it tends to go to areas that are already darker than the rest of the skin. These areas include the genital area, axilla (under-arm) area, and Areolae, as well as other areas such as inner thighs and the face. We can only guess as to why the Areolae increase in size, but part of it is because the breasts are increasing in size as well.

Notice in the photo montage above (PIC #1) that follows the woman through her pregnancy that as her pregnancy progresses, her Areolae become darker and slightly larger in diameter.

When people gain (or lose) a large amount of weight in a short period of time, it can cause what we call Stretch Marks to form on the skin. They can stay forever or they can reduce in appearance, depending upon diet, exercise, massage, skin conditioners, etc. Most only feel good but some help with the marking can be had by these efforts.


Increasing Vitamins C and E and Zinc and Silica in your diet can be helpful in keeping your skin healthy and possibly keep stretch marks to a minimum.


PIC #4 illustrates those Stretch Marks that can appear on breasts. This can happen when gaining or losing weight in general, if it happens quickly, but it often happens due to pregnancy because breasts can increase in size by one or two cup-sizes within months, and that can result in Stretch Marks.




Stretch Marks can be on the belly as well, for the same reason. As the woman's abdomen increases in size to keep up with fetal growth, the skin ends up being stretched and Stretch Marks show up. These happen more often the on the breasts, and they happen just from losing and gaining weight from dieting.

This image, plus a more involved explanation of pregnancy-related issues can be found on BabyCenterBlog:





PIC #5 Notice in the image  (PIC #3) above, there is a line that comes up the belly of the woman, from her pubic hair to her navel and a little beyond. That is called Linea Nigra, and is caused by the same melanocyte-producing hormone from the Placenta. It can be very distinguishable or barely visible, or quite bold and visible. This is another example of Linea Nigra:









Below is another composite of one woman going through her pregnancy. This one also progresses from the right to the left. She is in her second month on the right, and she is in her ninth month on the left. Notice that her Areolae do not seem to get much darker. The darkening seems to happen more in women of darker skin color.




PIC #6  In the composite above we can also see the change in the woman's posture, going from standing straight up and down on the right side picture to having to arch her back and lean slightly backward as we move left. This is because her center of gravity shifts forward with the increase of weight in her abdomen.

Here are several other images of women that are late in their third trimester who find it more comfortable to stand when they are leaning back more than they usually would. You can imagine that their stride will also be different with this weight-shift going on. Time for 'sensible' shoes.