Congratulations, you’re pregnant! Here’s how to better understand how your fetus is developing during the next nine months.
Pregnancy is a miraculous time! During nine months of rapid growth, one cell develops into a complete and functioning infant – your newborn baby. Fetal development is marked by monthly progress. Expectant moms change, too.
The following timetable provides a way to follow nine months of growth.
The 1st Trimester
Mom’s 1st Month: What to Expect
During the first month, mom-to-be misses a menstrual period, suggesting a possible pregnancy.
Hormonal changes may cause queasy feelings, especially upon awakening – hence the term “morning sickness.” Eating small, frequent meals and easily digestible foods can help with the queasiness, or try a cup of ginger or herbal mint tea. An occasional antacid may be used to ease indigestion, but some antacids can lead to fluid buildup, so seek your doctor’s advice first. Unfortunately, there are few over-the-counter solutions for morning sickness that actually work. You also start urinating more often. As your body prepares to nurse the newborn, your breasts feel tender and swollen.
While you may be unaware of the phenomenal event occurring in your body, amazing things are happening. The fertilized egg travels from the fallopian tube to the uterus and attaches itself to the nutrient-rich endometrial lining. These two cells then multiply 10,000 times to form a tadpolelike shape called an embryo that measures about a quarter inch in length. At conception, such inherited attributes as hair and eye color and body build are genetically encoded.
Stem cells differentiate to form fully functional heart, brain, blood, nerve, liver and immune cells. The head is bigger than the rest of the body; tiny spots delineate where the mouth, eyes and nose will develop. Little buds indicate where arms and legs will grow. Around the 25th day, the heart starts to beat.
The chorionic villi that are the early version of the placenta, and the umbilical cord, the fetus’s lifeline connection to the placenta and mother, are working to supply oxygen and nutrients.
By the end of the first month, the embryo is a half inch in length and weighs less than an ounce.
Mom’s 2nd Month: What to Expect
Your morning sickness and urge to urinate may worsen during the second month, but for most women, these symptoms soon subside. You may start craving some unusual foods or experience a change in your sense of taste and smell.
Vaginal spotting often appears at the time of implantation, but is unlikely to again. If you continue to spot, consult your physician immediately. If your doctor is not worried about the spotting, just use minipads if you feel you need protection. Your body is busy growing a new life so you may feel fatigued and need more sleep than usual; this is a natural response to changing hormone levels.
Now, about an inch long, the embryo develops body systems and organs, the inner ear, and bones. Arms with wrists, elbows, hands, and fingers, and legs with knees, ankles, feet, and toes begin to grow, but fingers and toes are webbed at this point.
Eyelids appear but remain closed. Genitals start to form.
The placenta and umbilical cord grow with the fetus. The placenta is a resourceful vascular organ that serves as the fetal lungs, digestive system, and kidneys during uterine life. The umbilical cord contains two fully developed arteries and a vein. The fetus receives oxygen, nutrients, antibodies, and hormones through the umbilical vein; the arteries carry waste products and carbon dioxide back to the placenta.
Mom’s 3rd Month: What to Expect
By the time you reach the second trimester, your appetite and energy level will improve.
As your hormonal system adjusts to its new role, you may experience some mood swings. The increased levels of the hormone progesterone may cause some indigestion. Again, an occasional antacid approved by your doctor may be used to ease indigestion.
During the third month the fetus, the baby-to-be, takes on the look of a recognizable human face with chin, forehead, mouth and nose. The head accounts for almost half of the body’s size, which now measures about three and a half inches in length and weighs just a little more than an ounce.
Stem cells continue to add functional detail to the major organ systems. The digestive tract begins to secrete bile and the intestines start to form. Bones and muscles begin to grow. The backbone can now flex.
Twenty dental buds appear in the gums; these will form the baby’s first teeth. The skin is almost transparent. The hands have developed more than the feet, and the arms are longer than the legs. Although not yet fully developed, all internal body parts are formed by the end of the first trimester. Using an instrument called a Doppler, your obstetrician may now hear the fetal heartbeat.
The 2nd Trimester
Mom’s 4th Month: What to Expect
By the second trimester, your belly begins to swell, and your skin may be rosy and glowing, caused by an increase in blood flow throughout your body. If, however, pregnancy is causing rosacea or acne, speak with your physician about using an over-the-counter product to help calm things down during this time. Products containing benzoyl peroxide are generally considered safe for pregnant women, but those containing salicylic acids should be avoided. Any other physical discomforts of the first trimester have probably vanished.
By the end of the fourth month, the fetus begins to look like a baby. Eyebrows, eyelashes, fingernails and a neck develop. The skin is red and wrinkled and covered with a waxy coating called vernix and fine downy hair called lanugo.
The kidneys now function and produce urine. The fetus’s first bowel movement, called meconium, is forming in the intestines.
An ultrasound now clearly shows the fetal gender if the fetus is positioned to reveal the developed external sex organs.
Mom’s 5th Month: What to Expect
If you haven’t felt the fetus move thus far, you will during the fifth month; these first movements are called “quickening.”
As the weight of the developing fetus rests on your intestines, you may experience some constipation, and hemorrhoids may develop. You may want to discuss the use of any products with your physician. Varicose veins in the legs may appear as well, so just be sure to rest and raise your feet at the end of the day or as often as possible.
Now more active, sleep and wakeful intervals are noticed by expectant moms. The fetus turns side to side or even tumbles head over heels. The fetal reflexes of swallowing and sucking are functional; if the thumb floats to the mouth, an ultrasound may show the young fetus sucking it.
The fetus can hear by the end of the fifth month and may respond to a loud sudden noise by jumping. Fingerprints and footprints are fully developed. Nails grow to the end of the fingertips. Testicles begin to descend from the abdomen into the scrotum in boys; eggs form in the ovaries of girls.
Still small at this stage, the fetus is about 10 inches long and weighs between half and 1 pound.
Mom’s 6th Month: What to Expect
You are more aware of your pregnancy now because the fetus is actively kicking, especially during the night. You may be able to feel the fetal foot or elbow against your abdomen as movements become stronger. Try drinking some warm milk before bed to help relax both you and your baby. As ligaments in your groin stretch, you may feel discomfort or pain on one or both sides of your abdomen. A word of caution during the second and third trimesters — beware of regular uterine cramping or pelvic pressure that is rhythmic. Call your doctor immediately and ask to be checked for premature labor, a potentially serious condition that requires treatment.
During the sixth month, the fetus produces antibodies as the immune system matures. Although fully formed, the lungs do not function; they are still developing alveoli, the final branchings that are the sacs where oxygen and carbon dioxide exchange takes place.
The brain rapidly grows. Eyes begin to open, and the fetus blinks for brief periods. Hair that will be present at birth appears on the head. The startle and grasping reflexes function.
The fetus now measures 12 inches and weighs 1 to 1 and a half pounds.
The 3rd Trimester
Mom’s 7th Month: What to Expect
Muscle strain in the sacroiliac region at the base of the spine may cause lower back pain. If possible, try to sleep on your side and support your back and legs with extra pillows.
Your breasts may secrete a sticky yellow substance called colostrum, or pre-milk, which prepares the breasts for nursing. Keep a supply of breast pads on hand to absorb leakage during this time and for the first few weeks after giving birth.
All organs continue to mature during this month. The fetus develops the ability to cry. The eyes easily open and close and can follow a light by the end of the seventh month.
The skin begins to smooth as the fetus adds subcutaneous fat layers and gains weight. At about 14 inches long and 2 to 2 and a half pounds, the fetus is still very small.
Mom’s 8th Month: What to Expect
Some women report swelling of the legs or ankles and some muscle cramping in the legs, but these symptoms are temporary. Discomfort from your increased size and fetal activity may cause insomnia. Again, a cup of warm herbal tea or milk may help you sleep better. Excessive weight gain or heredity can cause abdominal stretch marks; a cream that aids elasticity of the skin, such as cocoa butter, may help prevent permanent stretch marks.
The fetus rapidly grows and gains weight. By the end of the eighth month, the fetus measures about 18 inches in length and weighs 5 pounds. With the exception of the lungs, the vital organs are mature.
Regions of the brain develop significantly. Bones harden, but the skull remains flexible and soft for delivery.
Taste buds develop, and the fetus can differentiate between sweet and sour.
The fetus starts hiccupping creating rhythmic thumps in mom’s abdomen.
Mom’s 9th Month: What to Expect
During the ninth month, the fetus moves into the birthing position, putting extra pressure on your bladder, pelvic region, and lower back. It’s important to rest frequently during this stage, putting your feet up, or taking naps whenever possible. A warm heating pad or cold packs may provide some relief. Your health care provider may also be able to suggest some easy exercises that will help with the discomfort.
Uterine tightening in the abdomen, called contractions, may be the beginning of true or false labor. In false labor, the body is practicing for the real event. In true labor, the contractions cause the cervix to thin and dilate.
The fetus settles into a head-down position awaiting birth. The lungs now are fully mature and ready to function independently. Regular fetal sleep patterns develop. The fetus gains about half a pound per week during the last month of gestation, layering fat tissue to protect the vital organs and provide warmth.
At birth, a normally grown baby weighs between 6 and 9 pounds and is about 20 inches long.
Planning for a Healthy Baby
During the first trimester when the major organ systems are formed, you may not know you are pregnant for part of this time; therefore, it is crucial for women during the childbearing years to use medications, alcohol and tobacco conservatively all of the time.
Nine months of gestation will pass quickly. Taking extra care of your health during pregnancy makes a lifetime of difference for your baby.
Adair R. Heyl, Ph.D., is an Assistant Professor, and Peter S. Heyl, M.D. an Associate Professor, at the Department of Obstetrics & Gynecology, Eastern Virginia Medical School.
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