Your Pregnancy Week-By-Week
The First Trimester of Pregnancy
For many women, pregnancy is a time of joy and planning ahead for the future. The first trimester is especially important in the development of the little life inside and can present special challenges for expectant mothers. Knowing what to expect can help ease worries and provide a useful framework for couples expecting a new arrival in the near future.
While the first two weeks after the last period are technically counted as part of the gestational period and are included in the first trimester, most women are not actually pregnant during this period. Ovulation typically occurs two weeks after the last period ends. Any aches, pains, or discomfort experienced during this period typically cannot be attributed to pregnancy.
During this week, fertilization occurs when sperm meets egg in the Fallopian tube. This love-at-first-sight story continues as the fertilized egg, or zygote, travels down the tube toward the uterus, dividing rapidly as it makes its way to the spot where it will spend the next nine months.
Implantation typically occurs during the fourth week of pregnancy. The zygote, now known as a blastocyst, attaches itself to the wall of the uterus and burrows inward slightly to begin the job of growing in earnest. The placenta begins to form during this week as well. Some women will experience the first symptoms of morning sickness during this week due to hormonal changes. While most women will not yet realize that they may be pregnant, this also marks the first point at which a positive result may appear on an over-the-counter pregnancy test.
For most women, this is the first real hint that pregnancy has begun. Hormonal changes are well underway at this point and can cause noticeable mood swings in some women. Inside the uterus, the embryo’s development has kicked into high gear and the brain, spinal cord and other internal organs have just begun to form inside the tiny mass of cells. The baby has finally grown large enough to be seen with the naked eye and is about 1/16 inch in diameter.
This is a busy week for embryonic development; the neural tube that runs along the baby’s back begins to close, allowing the heart to begin pumping blood throughout the circulatory system. Small buds appear where arms and legs will soon grow, and internal development continues to progress quickly. During this week, morning sickness and food cravings may keep expectant mothers in constant motion between mad dashes to the bathroom and trips to the refrigerator.
The developing embryo may not be ready for his or her close-up, but during week seven the head begins to take shape and take on recognizable facial characteristics including eyes, ears and nostrils. Arms have also begun to form and the baby’s body is now typically about 1/3 inch long. Women may experience mild discomfort due to tenderness or swelling in sensitive areas; occasional bouts of nausea continue to occur during this week.
While first-time mothers will probably not show outward signs of pregnancy yet, the uterus begins to expand to make room for the growing baby and most women will notice that their favorite jeans and slacks are becoming tight around the waistline. The first prenatal appointment typically occurs around this time, and the baby’s digestive and skeletal systems begin to form during week eight and nine.
Swollen, sensitive breasts and frequent bathroom breaks can cause significant discomfort for mothers-to-be during week nine; additionally, some women may experience breakouts reminiscent of adolescence during this time period. Changes in the mother’s level of sexual desire are also common during the later stages of the first trimester due to wildly fluctuating hormonal levels. Inside the womb, the baby continues to grow and bone structures become more defined, with fingers appearing during this week.
While some babies begin to move around inside the uterus as early as the seventh week of pregnancy, during week ten this motion becomes more constant and reliable. Morning sickness may ease up during this week of rapid growth and development for the baby as hormone levels begin to stabilize and the body adjusts to the pregnancy.
This week is especially important because it marks the baby’s transition from embryo to full-fledged fetus. The baby is about two inches long now and displays more pronounced facial features; liver development also takes off during this crucial stage of development. Some prenatal tests are typically done at this stage to determine the health and well-being of the baby.
Ultrasound images of the developing fetus during the twelfth week of pregnancy show a recognizably human face with eyes, nose, and mouth. Almost all of the organs and physical systems are in place; hair and fingernails begin to grow during this final week of the first trimester. Expecting mothers may experience headaches and occasional weakness; proper nutrition and plenty of rest can help alleviate these symptoms in most cases.
Second Trimester Of Pregnancy
The second trimester of pregnancy is an exciting time for most expectant mothers, with major changes taking place both inside the womb and in the mother’s body. Most women experience fewer episodes of morning sickness during the second trimester and may feel more energetic as a result. Prenatal care visits become eagerly anticipated events for many expectant parents as the baby grows and develops; Doppler technology can allow mothers and fathers-to-be to hear their baby’s heartbeat and sonograms can sometimes even offer an early glimpse of the baby’s face.
By the thirteenth week of pregnancy, most of the baby’s vital organs are already in place. Vocal cords form during this period, as do tissue structures that will eventually become bone and cartilage. The baby is rapidly increasing in size; this expansion can stretch the uterus and create discomfort and cramping in some women.
At three and a half inches long, the fetus is beginning to look more and more like a real baby. The baby’s eyes have begun to move closer together toward the front of the face and hands and feet may start to move in what appear to be purposeful patterns. Many women notice significant swelling in their breasts at about this time; this is part of the body’s effort to prepare for the task of breastfeeding ahead.
Bone growth continues during the fifteenth week. At this point, an ultrasound may show tiny ribs forming as well as arms, legs, and other skeletal systems. Babies often begin instinctively sucking their thumbs at this point, causing dismay for some expectant parents and joy for orthodontists everywhere. The mother may experience an odd sensation beginning this week; the uterus begins to rise into the abdomen, putting pressure on other organs and creating mild discomfort in the process.
During the sixteenth week babies begin to develop rudimentary muscle structure, especially in their faces and hands. This growth allows babies at this stage of development to make expressions similar to those parents will see for years to come. Mothers-to-be may experience some swelling of the ankles and feet due to increased weight and stress on these parts of the body.
The baby is now a little over five inches long and about the same size as the placenta. The adorable layer of baby fat begins to develop during this time, adding a protective buffer zone between delicate skin and developing muscles. This period is a time of rapid growth for expectant mothers as well, with weight gain typically hitting its peak during the next few weeks.
Some first-time mothers begin to feel slight fluttering motions inside the uterus as early as week eighteen. As the baby’s bones grow and harden, its movements become gradually more noticeable. The point at which these movements can be sensed by the mother is referred to as quickening and often represents a joyful step forward for parents eager to meet their new arrival. During this week, babies often begin to hear sounds from outside the womb as their ears develop more fully.
As well as being covered with a thin layer of downy hair called lanugo, the baby’s skin now forms a protective coating known as vernix. This white, waxy substance protects the delicate skin against prolonged exposure to fluids inside the uterus and typically remains until birth. An ultrasound may be able to determine the gender of the baby with a fair degree of reliability at this point in the pregnancy.
This week marks the halfway point of pregnancy and is typically a time of constant motion for the growing baby inside. Babies can hear their mother’s voice as well as other loud noises outside and often respond with a healthy kick. Expectant mothers may feel a little cramped for internal space as the uterus continues to expand and press upward into the abdomen.
Babies begin to swallow amniotic fluid at about this time; this can lead to a rapid but temporary increase in his or her weight. All of the baby’s vital organs and limbs are in their proper places by the twenty-first week; while legs and other body parts will grow bigger, the baby’s body is essentially complete at this stage of pregnancy. Most women are showing visible signs of pregnancy at this point as well.
Most babies weigh around a pound and are making their presence felt with kicks and punches by week twenty-two. The extra weight and displacement of organs may cause severe backaches and fatigue for some mothers; rest and a bit of pampering can work wonders in helping to relieve these symptoms.
This week marks the first point at which babies can be considered viable, or potentially able to survive outside the womb with proper medical treatment. Hair begins to become apparent on the baby’s head and can sometimes be seen in ultrasound images. The baby’s unique fingerprints and footprints form during this week as well.
The last week of the second trimester is a time of rapid growth and weight gain for the developing baby. Mothers often undergo a glucose tolerance test during this period; this can identify cases of gestational diabetes, a potentially serious condition that can affect the health of mother and baby alike. With proper treatment, however, gestational diabetes can be controlled and managed successfully, helping to ensure the delivery of a happy, healthy baby just twelve short weeks from now.
Third Trimester Of Pregnancy
The third trimester marks the home stretch of pregnancy and is a time of rapid growth for both baby and mother. Most women experience some discomfort during the final stages of pregnancy due to weight gain and changes in how that weight is distributed; fatigue, dizziness and minor aches and pains are to be expected during these last months before delivery.
At this point, the uterus is roughly the size of a basketball and may be causing significant discomfort as it expands into the upper abdomen. Some mothers may experience shortness of breath as a result; balance may be adversely affected as well. The intricate structures of the baby’s spine are taking shape and nervous system structures are beginning to form and grow inside his or her body.
By the twenty-sixth week, most babies weigh around two pounds and are eight or nine inches long. This week is critical in lung growth and development; blood vessels and air sacs begin to form to prepare the baby for life in the outside world. Stretch marks may begin to appear around this time; liberal use of cocoa butter or other moisturizers can help minimize these marks and increase the elasticity of the expectant mother’s skin.
Sometime around week twenty-seven the baby’s eyelids will open for the first time and his or her retinas will begin to develop. A great deal of brain development takes place at about this time as well. While experts are divided on the value of prenatal enrichment activities, many parents choose this week to begin exposing their unborn child to Mozart, foreign languages, and other sounds intended to expand their mental capacities. Many babies can recognize their mother’s voice at this age and will respond by kicking or moving inside the womb.
Many mothers-to-be experience heartburn and indigestion during this period due to pressure on the stomach from the upwardly-mobile uterus. The baby’s kicks are becoming stronger and may be visible through the abdomen. As the space available for the growing baby becomes more cramped, the baby typically begins to move more often and with more force than in previous weeks.
The baby’s senses continue to develop and sharpen during the twenty-ninth week; hearing improves and the baby can move and focus his or her eyes at this point. Ultrasound scans may show a healthy head of hair and perfectly formed fingernails; at this point the baby’s bones are all in place but will continue to harden for several months after delivery.
At three pounds and nearly eleven inches long, the baby is now taking up a significant amount of room. Expectant mothers may be experiencing difficulty in finding a comfortable sleeping position at this point; most doctors recommend sleeping on one side and using pillows to help to support the abdomen in order to achieve the most restful sleep.
Most of the baby’s major internal organ systems are fully developed by this stage of pregnancy; only the lungs still require additional time to grow and mature. Bone marrow is producing red blood cells for the baby and the digestive and endocrine systems are essentially complete at this point.
As the baby’s lungs continue to grow and develop, most babies begin to practice breathing inside the uterus. By this point, most expectant mothers will have experienced at least one or two episodes of Braxton Hicks contractions; these painless precursors to labor are the body’s way of preparing for the genuine article. They may become more frequent and of longer duration during and after this week of pregnancy.
Amniotic fluid within the uterus has reached its peak volume during week thirty-three; mothers typically will gain about one pound per week from this point forward in pregnancy. Inside the womb, the baby’s eyes have developed sufficiently to be capable of detecting light if any were present. Some women experience periodic loss of appetite due to constant pressure on the stomach during this period.
The baby’s immune system kicks into action this week with white blood cells providing added protection for developing systems. From this point forward, most changes in the baby’s body are directly preparing for the upcoming delivery and exposure to the outside world. Fatigue, swollen ankles and backaches cannot dampen the spirits of most expectant mothers this week, but a few pre-delivery jitters are perfectly normal as the due date approaches.
At approximately five pounds and twelve to thirteen inches long, the baby has settled into a regular sleep-wake pattern which may or may not coincide with the mother’s schedule. At this stage of pregnancy obstetricians may begin checking the dilation of the cervix on each visit in order to determine whether labor is likely in the near future.
Most obstetricians recommend weekly visits by this week if they haven’t started already. Expectant parents should be alert for any changes in the strength or frequency of the baby’s movements; significant changes may indicate problems that should be addressed with the obstetrician immediately.
Most mothers are anxiously awaiting their due dates by this point. Babies born during or after week thirty-seven are considered full-term and typically require no special precautions if delivery occurs during this period.
The baby has developed an impressive kung-fu grip and is practicing grasping; the startle reflex is also present and retinal control has developed enough to react to bright and dim light. The average weight for babies at this stage of pregnancy is around six and a half pounds.
Most mothers will experience relief from the overwhelming pressure on their diaphragms this week as the baby settles downward into the position it will maintain until delivery. Babies typically stay in this head-down position for the remainder of pregnancy. For mothers, easier breathing comes with a price; many women experience pressure on their bladders that can lead to emergency bathroom runs during this time period.
The due date has arrived; while many mothers deliver a week or so before or after their scheduled delivery date, this week holds special importance for many expectant parents. The baby is ready to face the outside world, and mothers and fathers-to-be eagerly await the arrival of this new addition to their family. Babies in the breech position may require Caesarean section surgery; this will be determined based on an evaluation by the obstetrician. Most babies will be delivered without incident via natural childbirth and will be ready to go home with their parents within a few days of delivery.