Pay Your BillGuide for a Healthy Pregnancy
HOW YOUR BABY GROWS
The first step toward pregnancy is ovulation, when an ovary releases an egg. The egg is swept into a fallopian tube. There a sperm fertilizes it, forming a single, complete cell. The fertilized egg starts dividing right away into an ever-increasing number of cells. The tiny bundle of cells travels down the fallopian tube to the uterus, where it burrows into the soft, nourishing lining about seven days later. This is called implantation.
Your clinicians will date your pregnancy from the first day of your last menstrual period (LMP). Most pregnancies last about 40 weeks. A normal range for pregnancy is 37-42 weeks. That adds up to nine calendar months. Pregnancy is divided by three trimesters. The first trimester is generally thought of as weeks one to 13, the second is weeks 14 to 28, and the third is weeks 29 to birth.
Below, we describe some of the many events that take place during pregnancy and explain how they may affect you.
The First Trimester
Weeks five to six
The fertilized egg is now called an embryo. It has a simple brain and spine, and its digestive tract has begun to form. By the end of the sixth week, the heart begins beating and the embryo is about ¼ inch long. The placenta, which will nourish your baby in the uterus, continues to develop. It is a spongy, disk-shaped organ attached to the wall of the uterus. The umbilical cord links the embryo to the placenta. Oxygen, nutrients, and many other substances circulating in your bloodstream pass through the placenta to your baby. The baby’s waste products pass back through the placenta to your bloodstream and are filtered out of your body.
A fluid-filled bag called the amniotic sac surrounds the baby. The amniotic fluid inside it is water and secretions from the fetus, placenta, and sac. This fluid will let the baby move freely within the uterus and cushion it against bumps and jars. It also helps the baby maintain a steady body temperature.
You don’t look pregnant yet, but you may start to feel pregnant. Your period is late. You may have early pregnancy symptoms such as extreme tiredness, tender breasts, and nausea. You may vomit occasionally
and need to urinate often. Many women notice mood swings.
Week eight
About an inch long, the baby is now called a fetus. All his major body organs and systems have formed, but are not completely developed. Eyes, ears, and facial features are forming. Between weeks 10-12, a clinician can usually start to hear a heartbeat using an ultrasound device.
Your body is still adjusting to the changes of pregnancy. You still feel the discomforts of the past month.
The amount of blood in your body increases. As a result, your heart pumps more blood than it did before
you became pregnant.
Week twelve
Most of your baby’s internal organs (like the heart and kidneys) are working. Legs and arms have formed, but are still small. Muscles are developing and the baby is active in your uterus, although you probably can’t feel him moving yet. The baby can open and close his mouth.
Nausea may start to ease off (though sometimes it lasts well into pregnancy). You may not need to urinate as often as in the earlier weeks of your pregnancy. Your breasts are heavier and still tender. It’s probably time to buy a larger bra and start looking for looser, comfortable clothes. If this is your second pregnancy, you may find yourself needing these clothes earlier. Because your abdominal muscles stretched during your first pregnancy, your next pregnancy may show sooner.
The Second Trimester
Week sixteen
Although only eight inches long, your baby is now completely formed. From now on, she will mature and gain weight. Her skin is pink and so thin it is almost transparent. She has fingernails and toenails.
You are probably beginning to feel more energetic, more like yourself. You are starting to look pregnant. Your nipples and the colored area around them (the areolae) may start to darken. A dark line may begin to appear down the middle of your stomach. It will fade sometime after birth.
Soon you will feel a sensation like fluttering or tiny bubbles. Clinicians call this first awareness of the baby moving quickening. If you are a first-time mom, you may not notice this until around 20-22 weeks. In later pregnancies, you may feel this sooner, anywhere between 14-18 weeks. For a few women, it happens even earlier. Mark the date you first notice it on your calendar and tell your clinician.
Week twenty
Permanent teeth are developing behind the already-formed baby teeth. A white, oily substance called vernix protects the baby’s skin. Your baby sleeps and wakes and can grip with his hands. He is eight- to 10-inches long and weighs between a half-pound to a pound.
Your breasts may start to leak drops of a cloudy, yellow, watery fluid called colostrum. When you breast feed, this will nourish your baby during the first few days after birth until your breasts start to make milk. (If you don’t notice drops of colostrum, don’t worry. Not all women produce it at this time.) You may start to feel discomforts of later pregnancy. You may be short of breath, for example, have heartburn, or leak urine when you laugh, cough, or sneeze. This is a good time to start practicing Kegel exercises to strengthen vaginal muscles that help support your bladder and uterus.
Week twenty-four
Around weeks 24-26, your baby can hear sounds. He hears your voice and may startle at sudden loud noises. His skin is getting thicker and is covered by fine, soft hair called lanugo. You will notice times when he is very active, followed by times of calm when he is thought to be sleeping.
This is the start of your biggest weight gain and your belly grows quickly. You may feel the baby’s movements high in your abdomen or low in your pelvis. Your pelvic joints and ligaments are softening to prepare for birth. This softening probably causes pain you may feel in your groin, above your pubic bone, and in your side, as well as brief, sharp pains in your vagina. You may notice your uterus gets hard occasionally with Braxton-Hicks contractions. They help prepare your uterus for labor. These contractions often happen more when you change position or if you are dehydrated. Usually, they aren’t painful. Your baby’s movements are a sign of its well-being. Once you can feel your baby move regularly, you should call your clinician if there is a day when the baby seems much less active than usual.
The Third Trimester
Week twenty-eight
Your baby grows quickly now and weighs close to three pounds. This weight gain includes fat under the skin. The baby’s brain is more developed. He has many taste buds and a strong sense of taste. With advanced medical care, babies born after 28 weeks of pregnancy almost always survive.
You may feel late pregnancy discomforts like swelling and breathlessness. As your breasts and belly grow larger, stretch marks may appear. After birth, they will slowly fade to a silvery white.
Week thirty-two
Your baby continues to mature and grow bigger and heavier. She kicks more strongly and can sense the difference between light and dark. Now that the baby is bigger, she presses on your internal organs. Pressure against your diaphragm (the muscle below your lungs) may cause even more shortness of breath. It can be hard to get comfortable and to sleep. Your Braxton-Hicks contractions may be getting even stronger, but probably are still not painful. As your uterus grows, your bowels get more sluggish, leading to a bloated, full feeling; heartburn and constipation are common.
Week thirty-six
Your baby is almost ready to be born. He now gains between one-quarter to one-half pound a week and has begun to fill out. He is about 18 inches long. If this is your first baby, he may begin to drop into your pelvis now and get ready for birth. In later pregnancies, this may not happen until you go into labor. If the baby drops, it may be easier for you to breathe and any heartburn may improve.
You also will feel increasing pressure in your pelvis and need to urinate more often since the baby is pressing on your bladder. Because there is less room in your uterus, movements may feel like kicks, jabs, or squirming and may cause discomfort. From now on, your prenatal checkups will be every week.
Week forty
Ready to be born, your baby is about 20 inches long and weighs between 5-10 pounds. Most of her lanugo has disappeared. She has moved into the lower part of the uterus and may press against your cervix.
Your belly is large enough to make moving around a major effort. Your cervix is softening to prepare for labor, and you may feel pressure low in your abdomen. Braxton-Hicks contractions are so much stronger that you sometimes may think you are in labor. You are probably not in true labor if your contractions are irregular and stop when you move or change position. Don’t be surprised if you don’t go into labor on your due date. Remember, only one in 20 babies is born on their due date. Most are born within two weeks before or after their due date.
Weeks forty to forty-two
If you have not yet given birth, special tests will be done to monitor the health and well-being of your baby. Labor is generally induced after 41 weeks and by 42 weeks at the latest if it has not started naturally.
