Pre-Conception: Women are born with more than 200,000 eggs in their ovaries. However, they will probably only release about 400 of them, beginning with their first period and ending when menopause. Each month, during the middle of the menstrual cycle, an egg reaches maturity. It is then released and is quickly sucked up by the tulip-shaped opening of the nearest Fallopian tube. The average egg lives only 24 hours, so it has to be fertilised soon if a baby is to be conceived. If the egg meets up with a healthy sperm on its way to the uterus, the two join and begin the process of creating a new life.
Unlike women, men are not born with a specified number of sperm. Sperm is made on a regular basis. From start to finish it takes about 64 to 72 days to create a new sperm cell and, and about 200 to 350 million are set free with each ejaculation. Sperm production starts in the testicles. To produce healthy sperm they have to stay at about 34ºC. Once the sperm is created, it is stored in the epididymis until it is mixed with semen just prior to ejaculation.
Day (or more likely night) 0: Conception!
Most sperm die on the way to the egg. Only one sperm, the strongest, can fertilise an egg. Once the egg is penetrated, a protective shield covers it to prevent any other sperm from entering. This is because the sperm and the egg each provide 23 chromosomes for a total of 46. These 23 pairs of chromosomes provide the DNA blueprint for a human being. The egg cannot accept anymore information after fertilization, or it would result in information overload. The fertilized cell would not know how to split correctly and it would not know what to make. Occasionally, two eggs are released and each are fertilized by a different sperm. This results in fraternal twins. The process of fertilization is complete within 24 hours.
Day 1: The fertilized cell will begin to divide in a process called cellular mitosis. The baby's gender was already determined by the sperm, and when the gender organs develop, the sex cells (sperm or egg) will divide by a similar process called meiosis. The fertilized cell will now travel down into the uterus.
Pre-Day 12: Implantation.
The embryo will implant itself in the wall of the uterus. In rare cases, the embryo will not make it all the way to the uterus and will implant in the Fallopian tube. This is referred to as an ectopic pregnancy. In all cases, an ectopic pregnancy will fail. If they are not treated, the Fallopian tube will rupture. Sometimes, the embryo will not implant at all and a woman will not even know she was pregnant. If no form of birth control was used, reasons for non-implantation usually relate to either the health of the mother or some form of damage to the embryo.
Week 3: On average, this is the earliest that a urine pregnancy test will indicate that you are pregnant. Pregnancy tests check for the amount of human chorionic gonadotropin or hCG in the blood/urine. There is always some hCG present in the body, but it increases dramatically when you are pregnant. Due to the amount of hCG they are testing for, urine tests usually do not give false positives. They have been known to give false negatives however. (I experienced that with my current pregnancy.) If a urine tests says that you are pregnant, the embryo has usually already implanted. Blood tests are more sensitive than urine tests as they test for lower levels of hCG. They can detect a pregnancy before implantation.
Week 4: On average, this is the earliest that a woman will know she is pregnant without a test. It is possible, although extremely rare, for a woman to make it more than half way through her pregnancy without suspecting she is pregnant. Usually, the reasons for this are health-related.
By now, the embryo has begun to develop organs. The neural tube, which will develop into the brain and nerves, is in place and the beginnings of a heart and circulatory system are also in place. The placenta has also developed.
Week 5: The heart begins to beat and blood begins to pump. The umbilical cord, through which the baby will receive its food, has also developed and the intestines have started to grow. The layer for the skin, hair, nails and sweat glands is in place and limb buds have also begun to develop.
Week 6: The eyes, ears, nose and mouth begin to develop.
Week 7: Hands with the starts of fingers can be seen, as can feet with toes. Eyelids, cartilage and bones, the appendix and the pancreas begin to develop.
Week 8: Breathing tubes extend from the throat to the lungs.
Week 9: The baby is now almost one inch long. Lips are forming. Fingers can now curve and grip.
Week 10: The baby is no longer referred to as an embryo, but is called a fetus instead. Spinal nerves are beginning to stretch out from the spinal cord.
Week 11: Fingers and toes begin to separate and hair and nails begin to grow. The diaphragm begins to develop.
Week 12: On average, this is the earliest your doctor or midwife will try to listen for the baby's heartbeat (although it may be heard as early as week 10). For a first-time parent, hearing the heartbeat for the first time is perhaps one of the most exciting moments in pregnancy. That excitement never really diminishes with subsequent pregnancies either.
Sex glands begin to develop. In extremely rare cases, a male is born immune to testosterone. Although testicles do develop, they don't develop properly and won't descend out of the body. In such cases, parents may mistake their child for a girl. I have found no instances of the same thing happening in girls.
Week 13: The baby is about 3 inches long and weighs only about an ounce. Fingerprints are now in place. A lot of people wait until this point to tell people that they are expecting.
I would never have the self-control.
This marks the end of the first trimester. For a healthy pregnancy, women should take folic acid to assist in proper neural development and calcium. Red raspberry leaf is also recommended throughout pregnancy as it is good for the uterus. If a woman is going to have a miscarriage, the first trimester is by far the most common time to have it. The effects of things such as chicken pox, measles, salmonella or e. coli food poisoning are also most extreme during the first trimester. It should be noted however that not all viruses, bacteria, drugs or other foreign substances cross the placental barrier. For example, a cold is unlikely to affect your growing baby.
On to the next three months.