Congratulations! Your baby has just been conceived!

The fertilized egg starts to divide (multiplying by 2 each time), as it moves from the fallopian tube to the uterus.

When it reaches the uterus, it is a ball of 32 cells, and it searches for a place along the uterus wall to implant itself.

Once conception occurs, your body releases a substance called Early Pregnancy Factor to prevent your body from treating your baby as a foreign invader.

After implantation, the blastocyst will secrete hormones that will cause your body to not shed the uterine lining (hence you will miss your next period).

You might experience some spotting or bleeding at the time the blastocyst implants into the uterus.

You probably won't be noticing any real changes in your body yet.

Implantation will occur if it hasn't already done so the week before.

Your baby is now an embryo, and the main part, the embryonic plate, is a two-layered disc. The top layer will become the main embryo and amniotic cavity, and the bottom layer the yolk sac.

A narrow line of cells known as the primitive streak appears, which is the future axis of the embryo.

The embryo is attached by a connecting stalk to the developing placenta, and this stalk will later become part of the umbilical cord.

A home pregnancy test on your urine may test positive by now.

You may start to experience pregnancy symptoms (e.g., feeling tired, having mood swings). However, many of these first symptoms resemble premenstrual symptoms, so if you haven't realized you're pregnant, you may mistakenly think they are just caused by your upcoming period.

Your intake of protein should double during pregnancy as protein is used to create new tissue. Make sure you also consume enough calcium (e.g., from dairy products and leafy green vegetables), as it is vital for the development of bones and teeth. Iron is also important to support your baby's increasing blood volume.

Your baby now has three layers (outer, middle and inner), and each layer will develop into different parts of the body.

It also becomes more pear-shaped, with the head region broader than the tail end.

A neural groove also develops along the axis, and is the precursor of the nervous system.

The heart and primitive circulatory system is also rapidly forming.

You're probably noticing that your period is late.

If you haven't already, you may begin to have pregnancy symptoms. Your breasts will become swollen and tender as milk glands multiply; you may need to use the bathroom more frequently as the growing uterus presses on your bladder; you may feel nauseated from "morning sickness" and experience headaches caused by rising hormones; you may feel hungry more often as your body now requires energy for two people.

The infamous "morning sickness" affects about 70% of all pregnant women, and doesn't only occur in the morning. Good thing is, it usually goes away by Week 13.

The embryo starts to curve into a C-shape, and the head and tail ends become very distinct.

The neural tube develops into the brain and the spinal cord.

First heartbeats begin sometime this week! It begins at around 85 beats per minute (bpm), accelerating up to around 175bpm around the 10th week, then gradually decreases to around 130bpm by the time of birth. Note that this is just the average and individuals can vary quite a bit.

The central nervous system and circulatory system develop rapidly

This week tends to be worse than the previous week, and if you didn't experience pregnancy symptoms last week, this may be the time you do.

However, remember that everyone is different. For example, some women may crave certain foods, whereas others may find even the thought of it unbearable. Also, many may start to gain weight, but others (especially overweight women) may lose weight instead.

Your breasts probably feel heavier, tingle, and the areola (dark nipple portion) may become darker. Try to stay clear of cat litter boxes, as there is a risk of toxoplasmosis which can cause genetic defects.

Your baby has a very prominent tail!

Two tiny buds (which will become the arms) have developed, followed later by leg buds.

The inner ear, nostrils, larynx and a mouth opening also begin to form.

The brain and head grows rapidly. The forebrain (responsible for memory, thinking and reasoning) is very prominent.

The pregnancy symptoms will likely be continuing throughout this week. You may experience abdominal cramps and spotting of blood as the embryo continues to implant itself firmly to your uterus. Some women mistake this spotting for their periods.

Your cervix will develop a mucous plug at the opening which seals off the uterus for protection. This will be discarded just before labor.

Try to avoid foods like soft cheese, unpasteurized milk, raw/undercooked meats (including hot dogs), raw eggs, raw shellfish, and pate. These foods are associated with certain dangers to the baby.

Tiny depressions have appeared where the eyes will form.

Your baby's hand and feet start to flatten out and now look like paddles.

The tail is beginning to shorten.

The brain's cerebral hemispheres are noticeable.

The heart begins to separate into four chambers.

Intestines start to form in the umbilical cord (yes, outside the baby's body!)

Your uterus is expanding and so is your waistline.

If this is your first pregnancy, you're probably not showing yet. Women tend to show earlier in subsequent pregnancies since the muscles and ligaments aren't as tight as the first time.

Some women experience breakouts of pimples and other skin problems, caused by hormonal changes as well as an increase in oil secretions. These often stop after the first trimester, or latest after delivery.

You may also experience some heartburn and indigestion as your body adjusts to pregnancy hormones.

There are signs of a baby genius forming - brain waves can now be detected!

You may start to see notches for future fingers and toes.

Joints also develop, and you may now see knees, ankles, and wrists.

Your baby's spinal trunk becomes straighter.

The beginnings of the buds that will develop into your baby's genitals may appear.

Intestines start to form in the umbilical cord (yes, outside the baby's body!).

The skeleton starts to ossify (harden).

If you haven't already, now would be a good time to schedule your first prenatal visit with the doctor. Many things will checked during the visit, including your urine, blood pressure, weight, family history. Sometimes, the doctor will conduct a full physical with blood tests, pelvic examination and a pap smear.

Nasal congestions are fairly common during pregnancy, and even nose bleeds.

Even though you may not feel up to it, it would benefit you greatly to exercise in order to improve blood circulation. Swimming and yoga are highly recommended.

Your baby may begin to move as early as this week, although you will not feel it until several weeks later.

The finger and toe notches on the hands and feet start to separate into webbed digits.

The neck develops and starts to straighten.

The nose (including nasal openings), upper lip and tongue are formed, and external ears start to take shape.

The morning sickness symptoms may begin to ameliorate slightly. If you may start to notice your veins more (e.g., in your tummy and breasts), it's because your blood volume increases by about 50% during pregnancy.

If your doctor has a Doppler, you may hear your baby's heartbeat!

Although you probably still won't be showing, you may notice your abdomen begin to pooch out, and that your waistline is slowly disappearing!

You may have found that your taste for foods has changed since becoming pregnant. Some foods you previously liked may now seem unappetizing to you.

Your baby has passed a critical stage! All major internal and external structures have formed, and congenital abnormalities are now unlikely to develop.

Your baby is now a "fetus," and will begin a period of rapid growth doubling in size over the next few weeks!

Your baby will look more human-like. The head is erect and rounded, the eyes move closer together, and ears move higher.

The fingers and toes have fully separated and are no longer webbed.

Over the course of your pregnancy, you will probably gain between 25 to 35 pounds (around 11 to 16kg), though this will vary depending on whether you were overweight or underweight before pregnancy

For the first trimester, you will probably gain between 2 to 5 pounds (around 1 to 2.5kg), made up of your baby's weight, the placenta, a larger uterus, amniotic fluid, increased blood volume, and larger breasts.

In the second trimester, average weight gain is around 13 pounds (around 6kg), and 11 pounds (around 5kg) for the last trimester.

Keep your focus on having a healthy diet rather than on your weight.

Your baby's side profile has become more distinct, with its chin and nose much more prominent now.

The brain structure has completed forming and the brain mass is increasing rapidly.

Reproductive organs are developing rapidly.

Fingernails start to grow.

By this week, you will probably have been feeling less fatigued and nauseated, though headaches and dizziness might continue or get worse with the increased blood flow.

Your uterus has been growing along with your baby and almost filling your pelvis.

From around this week, your uterus will begin to shift up and forwards, so it won't be pressing on your bladder as much.

However, as your uterus grows, the ligaments that hold up your uterus expand to accommodate it, which may cause you to feel some abdominal ache now and again.

Your baby's vocal cords are beginning to form. Not long more and your baby will be able to make sounds!

Reflexes are being developed, and the hands are becoming more functional.

Sockets for all twenty teeth have formed in the gums.

Your baby's liver begins to carry out its functions of cleansing the blood, storing nutrients, and providing needed chemicals.

The tail has completely disappeared.

As your first trimester comes to an end, most of the difficult early symptoms are over (or soon will be).

The risk of miscarriage is also greatly reduced now, so sit back, relax, and enjoy the rest of your pregnancy!

The pregnancy hormone hCG has been increasing oil gland secretion (which sometimes results in acne). Together with greater blood volume in your blood vessels, your skin may look smoother and more flushed, which some call the "pregnancy glow."