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| Home > Reproductive Anatomy > Pregnancy Calendar > The First Trimester
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| | The First Trimester in Preganancy
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During this period all the fetal organs develop and start functioning. This is the period which puts maximum demand on you in terms of physical and emotional adjustments.
The First Four Weeks of Pregnancy
About the time your next period is due is when pregnancy tests begin to pick up the first traces of hCG in your urine or blood. A positive test can send you through a whirlwind of emotions, both positive and negative, no matter how long you`ve planned for pregnancy or if it`s a pleasant surprise.
Expectant Mother
Within days of getting a positive result from a pregnancy test, you`ll need to call your physician and set up an appointment for your initial prenatal visit. During your visit, You will have a thorough physical exam and a review of your medical history and you will be given an estimated due date for delivery.
You may have noticed only some breast swelling or tenderness, or an ache in your lower abdomen. And you have missed a menstrual period. The remarkable changes that you will experience have just begun.
Embryo
 Fertilization of the ovum with the sperm results in a single cell called zygote. The zygote spends the next few days traveling down the Fallopian tube and divides to form many attached cells. Within the first thirty minutes it begins dividing into two cells, then four, eight, sixteen, and so on. A ball of cells is produced, each cell including a copy of the genes that will guide the development of the baby. By the end of two days there are about 32 cells forming a cluster called the morula. With additional cell division, the morula becomes an outer shell of cells with an attached inner group of cells. Now the developing baby is in the blastocyst stage. The outer group of cells will become the membranes that nourish and protect the inner group of cells, which will become the embryo (the next stage for the future baby). It takes about five days for the waving movements of tiny hairs (the cilia) and the contractions of the fallopian tube to propel this rapidly developing life along the tube to the uterus, implants into the uterine wall in the upper part of the uterus on about day six. At this point in the mother`s menstrual cycle, the endometrium (lining of the uterus) has grown and is ready to support a fetus. The blastocyst adheres tightly to the endometrium where it receives nourishment via the mother`s bloodstream. The blastocyst develops tiny, root like projections (chorionic villi) that penetrate and extract nourishment from the uterine lining. The endometrium becomes thicker and more vascular. At the end of four weeks, chorionic villi extend well into the uterine lining and become an early placenta. Fetal blood circulates through this root like formation while your blood circulates into the spaces (inter villous spaces) surrounding the villi. A thin membrane separates the two blood streams and normally they do not mix. Because of placental chemicals and hormones, mom`s period will not normally start. These also prevent mom`s body from attacking the embryo as foreign tissue.
The fetus, placenta, and amniotic sac and fluid are formed through a complex process of cell division and differentiation. The amniotic sac surrounds the blastocyst. Later the fluid within the sac protects the fetus by acting as a buffer, maintaining an even temperature, and allowing for easy movement. By the 25th day, the circulatory system of the baby is closed and the heart now begins to beat, pumping blood throughout his tiny body. A primitive nervous system, with a brain and a spinal column, begins to form. Muscles and the backbone are forming. On the twenty-sixth day, arm buds appear and two days later, leg buds appear.
The 5th To 14th Weeks of Pregnancy
Fetus
 The embryo is now further developed into half the size of a pea. It has a head with eyes, ears and a mouth forming. Pigment is produced that make the eyes darken. In 35 days, Five fingers can be seen on the hand. Kidneys, liver, digestive tract and a primitive umbilical cord start developing. By day 40, brain activity can be detected and recorded.
By the end of week 6, the brain is beginning to control the movement of the baby`s muscles and organs. Reflex responses have begun. The baby`s liver is now taking over blood cell production.
By the 7th week, the embryo moves spontaneously. The jaw, including the buds of the milk teeth, is formed. Between forty-six and forty-eight days the first true bone cells replace cartilage in the skeleton. Although the unborn child`s sex is determined at the time of conception depending on whether the fertilizing sperm carried X or Y chromosome, the anatomy of the male and female baby is same until the fetus is about seven weeks old. Between the developing leg buds is a slit with a knob of tissue, the genital tubercle. There are two embryonic sex glands within the abdomen of the embryo. For a male embryo, the existing Y chromosome stimulates these sex glands to begin producing androgens, male hormones that cause the two sides of the slit to join, forming the scrotum and also causes the genital tubercle to develop into a penis. In late pregnancy, the testicles descend from the abdomen into the scrotum. In the female, the embryonic struc-tures take the female form-the slit becoming the vulva (or external genitalia), the genital tubercle becoming the clitoris, and the sex glands remaining within the baby as ovaries.
At the end of 8th week, the embryo is complete. Embryologists have determined that when the first bone cells appear in the upper arms, the embryonic period is complete. The baby is called a "fetus" from this point on. Every organ is present. In fact, the heart has been beating for more than a month. Taste buds are forming. The new body also functions: the brain sends out impulses that coordi-nate the functions of other organs, the heart beats strongly, the stomach produces digestive juices, the liver manufactures red blood cells, and the arms move. Thumb sucking may even have begun. The face has eyes, nose, ears, and a mouth with lips. a tongue, and tooth buds in the gums. The arms have hands with fingers and fingerprints. The legs have knees, ankles, and toes. The embryo grows about one millimeter a day, with different parts developing on different days.
By the end of the 9th week, there is evidence of your child`s unique fingerprints. The fetus will curve his fingers around an object placed in his hand. By the 10th week, your baby can squint and frown or smile. He can swallow and practices with the amniotic fluid.
At the end of the 1st trimester, the fetus is considerably active. All systems of the baby are working. S/he sleeps and wakes, moving vigorously. Please note you may not be able to detect these movements. S/he urinates. Drops of sterile urine mix with the amniotic fluid, which is exchanged and replaced about every three hours S/he also breathes amniotic fluid to help his/her respiratory system development. Taste buds and vocal cords work. No sounds are produced nor actual breathing done because the fetus is in a watery environment. The sex of the baby can now be seen. The baby can hear.
By this time the baby is about three inches long and weighs about one ounce.
Placenta
 The term `placenta` originates from the Latin word for `flat cake`. In everyday speech though, the placenta is generally referred to as the `afterbirth`.
Placenta begins developing at implantation of the blastocyst and by the third month of pregnancy, it is completely formed. During the 9 month period it provides nutrition, gas exchange, waste removal, endocrine and immune support for the developing fetus. It is through the placenta that oxygen and nutrients such as dextrose, protein, fat, water, vitamins, and minerals are passed from you to the fetus. Although the placenta provides adequate immune support against most bacteria, most viruses and drugs cross from the mother`s bloodstream to the fetal system. Waste products from the fetus are exchanged through the placenta and are carried by your blood to your kidneys and lungs for excretion.
Expectant Mother
The new demands on your energy and because of the subsequent shift in your rate of metabolism may make you feel very tired and you will be requiring more sleep. You may suffer from the so-called morning sickness (queasiness, nausea or vomiting) at any time of the day or night. As explained before under signs and symptoms of pregnancy, it caused by the high concentration of hCG in your body produced by the developing placenta. Your physician can recommend ways and means to cope with this affliction.
The glandular tissues in your breasts that produce milk do not fully develop until you become pregnant. As the pregnancy progresses, the levels of estrogen, progesterone, and other hormones increase. They will cause your breasts to enlarge. The glandular tissues will develop. The area around each nipple, areola, will become darker. Little bumps, called Montgomery glands, become more prominent in this area and enlarge to produce more lubricant for the areola. Your breasts will become sensitive to touch and you will feel a tingling sensation.
You will also feel the urge to pass urine more frequently. It is due to the pressure from the enlarged uterus on your bladder.
Your vagina and cervix become bluish in color (Chadwick`s sign). The cervix will become softer. Vaginal secretion will increase.
These changes are miniscule in size and so you will feel more different than you will look. The early months of pregnancy are filled with emotional upheaval. You will have extreme mood swings and may be quite difficult for you and your partner to understand.
Expectant Couple
 Pregnancy gives rise to a mixture of emotions in you and your partner. Sometimes you will feel proud in your ability to give birth to a child and then again, you will think of the responsibility that it entails. You will be apprehensive about somewhat losing your independence, of changes in your relationship with other, about your ability to be good parent. It is better to discuss and share your thoughts with your partner. Remember he is also going through a whole gamut of emotions.
Your attitude towards sexual activity also changes in the first trimester. You may feel more inclined towards sex, since you no longer need to worry about either trying to get pregnant or trying to avoid pregnancy. Then again, your interest towards sex may reduce if you get affected by the irritating symptoms of early pregnancy like morning sickness, breast soreness, fatigue or fear of miscarriage. You and your partner should discuss each other`s feelings towards sexual activities and do what is mutually desired.
If you have miscarried before or have bled through the vagina during the pregnancy, it is advisable to avoid sexual intercourse.
The calendar will assist you to help you understand and anticipate the changes.
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