First Trimester

WEEK 1 & WEEK 2
14 days before the end of each period cycle, follicles mature and rupture, releasing anpregnancy calendar – conception egg that will travel down the fallopian tube, where it awaits fertilization. The fertilization must be taken place within 24 hours or it will begin to disintegrate and the survivor of sperm is 48 hours after intercourse. A single cell call zygote will be created when egg and sperm join together.

WEEK 3
The fertilized egg begins to divide into multiple cells as it moves from the fallopian tubes to the uterus. At this moment it doesn’t look like a fetus or baby; it’s just a group of about 100 cells multiplying and growing rapidly. The outer layer of cells will become the placenta, and the inner layer will become the embryo.

WEEK 4
At this stage the baby is still very small. The baby is now an embryo. The embryo, probably in about its second week of development, has multiplied to about 150 cells. Your baby is being nourished by secretions from the uterine lining. Layers of cells already are specialized according to functions. The outer layer will become the nervous system, skin and hair; the inner layer will be the breathing and digestive organs; and the middle layer will become the skeleton, bones, cartilage, muscles, circulatory system, kidneys and sex organs. You may start to experience some of the pregnancy symptom like morning sickness, breast tenderness, water retention, or constipation.

WEEK 5
A positive sign will be shown if home pregnancy test is used at this stage. The test is more accurate in the morning. Your embryo still hasn’t grown much. Heart, brain, spinal cord, muscle and bones are beginning to develop. The placentas, which will nourish your baby, and the amniotic sac, which provides a warm and safe environment where the baby can move easily, are still in the formation process.

WEEK 6
The baby will be having remarkable changes this week as eyes and limb buds are forming. A heartbeat can sometimes be detected by an ultrasound around now. This is also an extremely important time in the development of your baby, since between 17 and 56 days the embryo is most susceptible to factors that can interfere with its normal growth. You may have gained a few pounds by now, but somehow it is normal to loss weight if you’re experiencing morning sickness.

WEEK 7
At this stage, the size of your embryo will double up, growing to between 0.44” and 0.52 inches, or about the size of a small raspberry. Leg buds and arm are present now. The heart and lungs are becoming more developed, as are the eyes and nostrils, intestines and appendix. By now the brain and spinal cord are growing from the neural tube. By now you’re really feeling the changes in your body. You may probably still experiencing morning sickness and the other symptoms of early pregnancy. These symptoms are caused for the most part by the rush of hormones in your body.

WEEK 8
Your embryo, now about in its sixth week of development, is about 0.56 to 0.8” from crown to rump. Facial features also continue to develop. Eyelid folds and ears are forming and even the tip of the nose is visible. Little fingers are starting to form and the arms and hands continue to lengthen and develop.

WEEK 9
The embryo measures about 0.9” to 1.2 inches. The baby arms continued to change, with elbows and wrists becoming more apparent. The head is more erect and neck is more developed. The baby begins to have some movement now. However, the movements are only visible during ultrasound and still can’t be feel by you.

WEEK 10
Your baby no longer an embryo, is now called a fetus” and measuring around 1.25 to 1.68” from crown to rump. This is a critical time in a baby’s development, as the essential internal organs and other parts of the baby are forming. Baby’s sex organs are developing, but you still can’t tell if it’s a male or female. If you’ve experienced mild nausea in the past weeks, it may start to subside now, however, everyone’s different.

WEEK 11
Your fetus, about the size of a large lime, measures about 1.75 to 2.4” from crown to rump and weighs about three-tenths of an ounce. Baby’s head is becoming more rounded and makes up half the length of your baby. This is the beginning of the fetal period, meaning that the embryo has developed into a recognizable human being and all major systems have been formed. Fingernails and toenails start to grow.

WEEK 12
The fetus now between three-tenths of an ounce and half an ounce. Toenails and fingernails are fully formed, and your baby’s job now is to continue getting larger and stronger for the rest of your pregnancy. If you have a prenatal check up this week, you may be able to hear your baby’s heart-beat with a device called a Doppler, but probably not with a regular stethoscope. You may be experiencing occasional headaches, dizziness and fatigue from hormonal changes. You may also notice that your clothes are getting a little bit snug around the waist as the uterus rises above the pelvis.

WEEK 13
This week marks the end of the first trimester. Your fully formed fetus, now in about its 11th week of development, measures 2.6 to 3.1” from crown to rump and weighs between half an ounce and seven-tenths of an ounce. The head is still disproportionately bigger than the body, little eyes move closer together and ears move higher up on the head. The face is starting to look more human. You may be able to feel your uterus just above your pelvic bone as it expands to accommodate your baby, placenta, and amniotic fluid.