Pregnancy - The First Trimester

Find out what's happening with your baby and your body during the first trimester of pregnancy.

The arrival of the fertilized egg
In the first Week of pregnancy there is no baby yet. For now, your uterus is preparing for the arrival of the fertilized egg, even though you can’t really tell for sure that the egg has successfully matched up with sperm until next month. While it’s hard to calculate the exact moment pregnancy begins, your conception date is considered to be two weeks after the last day of your last menstrual period. It really all comes down to the moment your egg meets the sperm.

Conception and fertilization

This Week you definitely ovulated, so the zygote starts its remarkable journey to a baby boy or girl! Within days it will divide into two cells, then four and so on, until the cluster will comprise around 100 cells. Some of the cells form the embryo, others the placenta. As it divides, the blastocyst starts traveling to your uterus a journey where it will implant itself in the uterine wall and grow for the next nine months. Your baby's appearance, sex and other characteristics are determined at fertilization.

Placenta and embryo are developing

Your embryo is no longer than one millimeter and no bigger than a poppy seed, but is busy developing at an incredible fast pace. Your embryo splits into two parts this week: half of it will become your son or daughter, while the other half forms the placenta, the lifeline that channels nutrients to your baby and carries waste away until the point of birth. The embryo has now three different layers of cells that will grow into specialised parts of your baby's body.

Baby’s heart beats for the first time

Your baby is now the size of an orange seed, at least twice as big as before. Your pregnancy hormone levels are now high enough to confirm that you are pregnant using a home pregnancy test. One of the first systems to be operational in your baby’s developing body is the circulatory system and of course, the heart, which you may even be able to see it beating on an early ultrasound. When you are 5 Weeks pregnant, your baby’s heart is made up of two small channels called heart tubes and they are already strong at work.

Baby's head takes shape
Your baby is now the size of the length of a sweet pea, measuring anywhere from a fifth to a quarter of an inch. For the first time, your baby's jaw, cheeks and chin are now visible. All those little indentations on both sides of the head are in fact the developing ear canals. Small bumps on the face will form the eyes and button nose in a few weeks time. Also taking shape this Week are the baby’s kidneys, liver and lungs, along with the heart, which is now beating 80 times a minute.

Baby's arms and legs are developing
Your baby's approximately a quarter of an inch in length now, about the size of a blueberry. At 7 weeks pregnant, most of that growth is concentrated in the head as new brain cells are generated at the rate of 100 per minute. Also, baby’s arm and leg buds begin to sprout and expand into hand, arm and shoulder segments and leg, knee and foot segments. Also forming this week are your baby's mouth and tongue. At this stage, even though your embryo is just one month old, it's already gone through three sets of kidneys.

Baby's Facial features are visible
At a length of about half an inch right now, your baby is the about the size of a raspberry and is growing at a rapid rate, a millimeter every day. You are able to see now an upper lip forming, the tip of the nose and tiny, thin eyelids. Also, his or her heart is beating at the incredible rate of 150 times per minute, about twice as fast as the adult heart beats. Even though you can't yet feel it, baby is making spontaneous movements as he or she twitches the trunk and limb buds.

The start of the fetal period
Your fetus is now about one inch long, the size of a cherry. Your little one is getting bigger every day, the head is about the same size as the rest of his or her body. The ears are much more prominent and some new organs liver, spleen and gallbladder are forming. Your baby is also making spontaneous movements of his or her arms and legs now that micro muscles are beginning to develop.

Baby's bones are hardening
Your baby is nearly an inch and a half long, the size of a prune. In fact, your baby went from an embryo to a full-developed fetus. Bones and cartilage are forming and the knees and ankles are shaping. The arms (complete with elbows) can flex already. The baby’s teeth are now beginning to form under the gums. Your baby's stomach is producing digestive juices, the kidneys are producing larger quantities of urine and, if your baby's a boy, he's already producing testosterone.

Fingers and toes are emerging
Your baby is the size of a brussels sprout and two inches long. By week 11 of pregnancy, baby has distinct human characteristics: hands and feet, ears in their final shape, open nasal passages on the tip of the nose, a tongue and palate in the mouth and visible nipples. The head is currently equal in length to the rest of the body and hair follicles are forming on the crown. The hands and feet have individual fingers and toes and by next week, the nails themselves will start to grow.

Digestive system is at work
Your baby weighs half-ounce, with a crown-to-rump length of about two and a half inches, about the size of a large plum. Your baby’s systems continue to mature for the next 28 Weeks. For one thing, the digestive system is beginning to flex its digestive muscle as it produces contractions.

Second trimester begins
Your baby is as large as a peach. In this stage, babies begin growing at different paces. Also, tiny bones are beginning to form in their arms and legs. Your baby's intestines are also in for some big changes, moving towards his/her abdomen. And to serve your growing baby's needs, the placenta is also growing. Also developing this week are the vocal cords. Because sound can't travel through your uterus, you won't be able to hear any sounds or cries just yet.

Second Trimester

Third Trimester

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