My husband and I had been trying to conceive for almost a year. I was delighted when my menstrual cycle was late. My husband, ever cautious, took a wait-and-see attitude. After a few days had passed without my menstrual cycle starting, I bought a home pregnancy test. My husband waited in the living room while I took the test that would tell us whether we were parents-to-be. Sure enough, a faint blue line appeared on the test. I showed it to my husband, who said excitedly, “It’s a maybe?” No maybe about it. We were expecting our first child! — Paula
Congratulations! And welcome to one of life’s most exciting adventures — pregnancy. Over the next 40 weeks, your body will undergo some amazing changes. Like most new moms, you may be a bit nervous about what’s in store. That’s perfectly normal. And, no doubt, you have many questions. What does my baby look like? How big is he or she? Is he or she going to be healthy? What do I need to do next? To help answer some of these questions, and to calm those jitters and fears, we’ll take you on a week-by-week journey, describing how your baby is constantly developing and changing. We’ll also explain some of the changes taking place within your body, so you know what to expect and can prepare for what’s ahead.
Pregnancy is a wonderful experience. Sit back (but not too much), relax (as much as you can), and enjoy the adventure to its fullest!
BABY’S GROWTH
The way care providers calculate the first month of pregnancy may seem a bit confusing. That’s because you don’t actually become pregnant until midway through the first month. It’s generally not until the end of week two that conception occurs — the official start of pregnancy. Prior to that, your body is getting prepared.
Weeks 1 and 2 It may seem a bit strange, but the first week of your pregnancy is actually the beginning of your last menstrual period before you become pregnant. Why is that? Doctors and other health care professionals calculate your due date by counting 40 weeks from the start of your last cycle. That means they count your period as part of your pregnancy, even though your baby hasn’t been conceived yet. Conception typically occurs about two weeks after the start of your last menstrual period.
Preconception During menstruation your body begins producing a hormone called follicle-stimulating hormone, which fosters development of an egg in your ovary. The egg matures within a small cavity in your ovary called a follicle. A few days later, after menstruation has ended, your body produces a hormone called luteinizing hormone. It causes the follicle to swell and burst through the wall of your ovary, releasing the egg. This is called ovulation. You have two ovaries, but in any given cycle, ovulation occurs from just one of them.
As the egg moves slowly into your fallopian tube, which connects your ovary and uterus, it awaits a fertilizing sperm. Finger-like structures at the junction between your ovary and fallopian tube, called fimbriae, catch the egg when ovulation occurs, keeping it on the proper course.
If you have intercourse before or during this time, you can become pregnant. If fertilization doesn’t occur, for whatever reason, the egg and the lining of your uterus will be shed through your menstrual period.
Fertilization This is when it all begins. Your egg and your partner’s sperm unite to form a single cell — the starting point for an extraordinary chain of events. That microscopic cell will divide again and again, and in about 38 weeks, it will have grown into a new person made up of more than 2 trillion cells — your beautiful new baby girl or boy.
The process begins when you and your partner have sexual intercourse. When he ejaculates, your partner releases into your vagina semen containing up to 1 billion sperm cells. Each sperm has a long, whip-like tail that propels it toward your egg.
Hundreds of millions of these sperm swim up through your reproductive tract. They travel from your vagina, up through the lower opening of your uterus (cervix), through your uterus and into your fallopian tube. Many sperm are lost along the way with only a fraction of the sperm reaching the fallopian tube. Fertilization occurs when a single sperm makes this journey successfully and penetrates the wall of your egg.
Your egg has a covering of nutrient cells called the corona radiata and a gelatinous shell called the zona pellucida. To fertilize your egg, your partner’s sperm must penetrate this covering. At this point, your egg is about 
of an inch in diameter, too small to be seen.
Up to 100 sperm may try to penetrate the wall of your egg, and several may begin to enter the outer egg capsule. But in the end, only one succeeds and enters the egg itself. After that, the membrane of the egg changes and all other sperm are locked out.
Occasionally, more than one follicle in an ovary matures and more than one egg is released into the fallopian tube. This can result in multiple births if each of the eggs is fertilized by a sperm.
As the sperm penetrates to the center of your egg, the two cells merge to become a one-celled entity called a zygote. The zygote has 46 chromosomes — 23 from you and 23 from your partner. These chromosomes contain many thousands of genes. This genetic material is like a blueprint, determining your baby’s sex, eye color, hair color, body size, facial features and — at least to some extent — intelligence and personality. Fertilization is now complete.
BABY’S SEX: CAN PARENTS CHOOSE?
Is there any way to influence a baby’s sex — increase your odds for a boy or girl?
The short answer is no. There’s not much the average couple can do to affect a baby’s sex. Countless old wives’ tales suggest that everything from a woman’s diet to sexual position during conception can affect a baby’s sex, but these theories remain unproved. Likewise, researchers have found that timing sex in relation to ovulation — such as having sex days before ovulation to conceive a boy or closer to ovulation to conceive a girl — doesn’t work.
Rarely, couples face the agonizing problem of knowing they could pass a genetic trait to a child of a specific sex — usually a boy. Under those special circumstances couples may use expensive, high-tech interventions to influence the chance of conceiving a girl. For example:
Preimplantation genetic diagnosis. With this technique — which is used in combination with in vitro fertilization — embryos are tested for specific genetic conditions and sex before they’re placed in a woman’s uterus.
Sperm sorting. Various sperm-sorting techniques — which require artificial insemination or in vitro fertilization — also can be used to reduce the likelihood of passing on a genetic condition, as well as select a child’s sex.
Despite the feasibility of these techniques, they’re rarely used in circumstances where choosing a baby’s sex for personal reasons is the only motivation.
Weeks 3 and 4 Once your baby is conceived, he or she gets to work right away. The next step in the process is cell division. Within about 12 hours after fertilization, your one-celled zygote divides into two cells and then those two each split into two, and so on, with the number of cells doubling every 12 hours. The cells continue to divide as the zygote moves through your fallopian tube to your uterus. Within about three days after fertilization, it becomes a cluster of 13 to 32 nonspecialized cells resembling a tiny raspberry. At this stage, your developing baby is called a morula. It now leaves the fallopian tube to enter your uterus.
Within four to five days after fertilization, your developing baby — now made up of about 500 cells — reaches its destination inside your uterus. By this time, it has changed from a solid mass of cells to a group of cells arranged around a fluid-filled cavity, and is called a blastocyst. The inner section of the blastocyst is a compact mass of cells that will develop into your baby. The outer layer of cells, called the trophoblast, will become the placenta, which will provide nourishment to your baby as it grows.
After arriving in your uterus, the blastocyst clings to the uterine surface for a time. It then releases enzymes that eat away at the lining of your uterus, allowing the blastocyst to embed itself there. This typically happens about a week after fertilization. By the 12th day after fertilization, the blastocyst is firmly embedded in its new home. It adheres tightly to the lining of your uterus, called the endometrium, where it receives nourishment from your bloodstream.
Also within about 12 days after fertilization, the placenta begins to form. At first, tiny projections sprout from the wall of the blastocyst. From these sprouts, wavy masses of tiny blood-vessel-filled tissue develop. Called chorionic villi, these masses grow amid the capillaries of your uterus and ultimately cover most of the placenta.
At 14 days after conception, four weeks since your last menstrual period, your baby is about 
of an inch long. It’s divided into three different layers, from which all tissues and organs will eventually develop:
Ectoderm. This top layer will give rise to a groove along the midline of your baby’s body, called the neural tube. Your baby’s brain, spinal cord, spinal nerves and backbone will develop here.
Mesoderm. This middle layer of cells will form the beginnings of your baby’s heart and a primitive circulatory system — blood vessels, blood cells and lymph vessels. The foundations for bones, muscles, kidneys, and ovaries or testicles also will develop here.
Endoderm. This inner layer of cells will become a simple tube lined with mucous membranes. It’s from this tube that your baby’s lungs, intestines and urinary bladder will develop.
YOUR BODY CHANGES
During this first month, you may not feel much different from normal. That’s because early pregnancy symptoms often don’t begin until midway through the second month.
What’s happening and where Even though you may not feel pregnant, don’t be fooled. There are many changes taking place in your body!
Week 1 In the time leading up to conception, it’s important to make lifestyle choices that prepare your body for pregnancy and motherhood and give your baby-to-be the best possible start in life. As you prepare for pregnancy, don’t smoke, drink alcohol or use drugs. If you take prescription medications, ask your care provider for advice regarding their use during pregnancy.
It’s also a good idea to take a daily vitamin supplement containing at least 400 micrograms of folic acid. Adequate folic acid will reduce your baby’s risk of developing defects in the neural tube, the component of the embryo that gives rise to the brain, spinal cord, spinal nerves and backbone. Spina bifida, a spinal defect that results in failure of your baby’s vertebrae to fuse together, is an example of a neural tube defect that can be largely avoided with adequate folic acid.
Weeks 2 and 3 As you ovulate and an egg is released into your fallopian tube, the hormones involved in the process — estrogen and progesterone — cause a slight increase in your body temperature and a change in secretions from your cervical glands.
Immediately after fertilization, the corpus luteum — a small structure that surrounds your developing baby — starts to grow and produce small amounts of progesterone. This helps support your pregnancy and keeps your uterus from contracting. Progesterone also promotes growth of blood vessels in the uterine wall, essential for baby’s nourishment.
Roughly four days after fertilization, finger-like projections that will become your placenta begin producing large amounts of a hormone called human chorionic gonadotropin (HCG). This hormone stimulates the ovaries to keep producing estrogen and progesterone, which cause changes in your uterus, endometrium, cervix, vagina and breasts. Eventually, placental tissue will become responsible for the production of estrogen and progesterone. The hormone HCG is first detected in your blood and shortly thereafter in your urine. Home pregnancy tests can detect it in a sample of your urine about six to 12 days after fertilization occurs.
By the time your developing baby travels through your fallopian tube and implants itself in the lining of your uterus — about a week after fertilization — your endometrium has grown thick enough to support it. As your baby implants, you may notice spotting, a scanty menstrual flow or yellowish vaginal discharge. You may mistake it for the start of your normal menstrual period. This spotting comes from the small amount of bleeding that can occur when your developing baby implants itself into the lining of your uterus. At this point you are officially pregnant, though it’s too early for you to have missed a period.
In these first days after fertilization, miscarriage is common — often happening before a woman even knows she’s pregnant. Scientists estimate that 3 of every 4 lost pregnancies are the result of implantation failure. In the first week to 10 days after conception, infections or exposure to harmful environmental factors, such as drugs, alcohol, medications and chemicals, can interfere with the implantation process. Most of the time, however, miscarriage is due to unknown factors beyond anyone’s control.
Week 4 Even this early in your pregnancy — just days after conception — your body is already undergoing significant physical changes.
Heart and circulatory system. Your body immediately begins producing more blood to carry oxygen and nutrients to your baby. The increase is greatest in the first 12 weeks, when pregnancy makes enormous demands on your circulation. By the end of your pregnancy, your blood volume will have increased 30 to 50 percent. To accommodate the increased blood flow, your heart begins to pump harder and faster, and your pulse may quicken by as much as 15 beats a minute. These changes are a big reason why you feel so tired early in your pregnancy. You may find that you’re ready for bed right after the evening meal, or that you need to nap during the day.
Breasts. One of the first physical changes of pregnancy is a change in the way your breasts feel. They may feel tender, tingly or sore, or they may feel fuller and heavier. You may think that your breasts and nipples are already starting to enlarge, and it’s possible they could be. These changes are stimulated by increased production of estrogen and progesterone.
You may also notice the rings of brown or reddish-brown skin around your nipples (areolas) begin to enlarge and darken. This is the result of increased blood circulation and growth of pigmented cells, and it could be a permanent change to your body. In addition, bumps, called Montgomery’s tubercles, appear on the areolas. They secrete lubricating and anti-infection substances that protect the nipples and areolas during breast-feeding.
Uterus. Not surprisingly, your uterus is rapidly changing. Its lining is thickening, and the blood vessels in the lining are beginning to enlarge to nourish your growing baby.
Cervix. Your cervix, the opening in your uterus through which your baby will emerge, already begins to soften and change color at this early stage. Your care provider may look for this change as confirmation of your pregnancy during your first examination.
YOUR EMOTIONS
Expect your emotions to be all over the place, because they will be. Pregnancy can be exciting, boring, satisfying and nerve-racking — sometimes all at once. You’re also likely experiencing new and unexpected emotions — some of them comforting and others unsettling.
Mixed feelings Whether your pregnancy was planned or unplanned, you may have conflicting feelings about it. Even if you’re thrilled about being pregnant, you may worry about whether your baby will be healthy and how you’ll adjust to motherhood. You may also have concerns about the increased financial demands of raising a child. Don’t beat yourself up for feeling this way. These concerns are natural and normal.
Mood swings As you adjust to being pregnant and prepare for new responsibilities you may be upbeat one day and feel down the next. Your emotions may range from exhilaration to exhaustion, delight to depression. Your moods can also change considerably over the course of a single day. Some of these mood swings may result from the physical stresses your growing baby is placing on your body. Some may simply be the result of fatigue. Your change in moods may also be due, in part, to certain hormones and changes in your metabolism.
To meet the demands of your growing baby, different hormones are produced at different levels throughout your pregnancy. Though the mechanisms aren’t well understood, the changes — sudden fluctuations in progesterone, estrogen and other hormones — likely contribute to mood swings during pregnancy. The effects of hormones from the thyroid and adrenal glands also may play a role.
There’s also no doubt your moods are strongly influenced by the support you receive from your partner and family.
Your partner’s reaction If you have mixed feelings about being pregnant, chances are your partner does, too. He or she may be exhilarated by the anticipation of sharing a loving relationship with a daughter or son. But, like you, your partner may worry about financial challenges or may fear that a baby will forever change your lifestyle. These feelings are normal. Encourage your partner to identify his or her doubts and worries and be honest about what he or she is feeling, both the good and the bad.
Your relationship with your partner Becoming a mother-to-be can take time away from your other roles and relationships. There may be times when your partner is interested in sexual activity and you aren’t. If you reject your partner’s overtures in the bedroom, your partner may view it as a rejection of him or her. In truth, you’re probably just tired, sad or worried. Misunderstanding and conflicts between you and your partner are inevitable and normal during pregnancy, just like any other time in your relationship.
Understanding and communication are the keys to preventing or minimizing conflicts. Talk openly and honestly with your partner so that you can anticipate and help minimize stress in your relationship.
SCHEDULING A PRENATAL CHECKUP
You’ve taken a home pregnancy test, and it says you’re pregnant. Now’s the time to set up your first appointment with the person you’ve chosen to provide your obstetric care during your pregnancy. Whether you’ve chosen a family physician, obstetrician-gynecologist or nurse-midwife, that person will treat, educate and reassure you throughout your pregnancy. Developing a strong relationship with your care provider starts now, at the very beginning of your pregnancy. Care providers enjoy the celebration inherent in pregnancy and birth and want to enhance your celebration of it, too. For more information on finding a care provider who’s right for you, see choosing a care provider in Chapter 1.
Your first visit to your care provider will focus mainly on assessing your overall health, identifying any risk factors for you or baby and determining how far along you are in your pregnancy.
Getting yourself prepped At your first appointment, your care provider will review your past and current health, including any chronic medical conditions you have and problems that you may have encountered during past pregnancies.
In the time before your first appointment, you may want to write down details regarding your menstrual cycles, contraceptive use, family medical history, work environment and lifestyle. Some care providers make the first part of this appointment a one-on-one conversation with just you — the mom-to-be — and later invite your partner to join you. This gives you an opportunity to privately discuss any health and social issues from your past that you may want to keep private.
This first visit is also an opportunity for you to ask questions. Make it easy on yourself by jotting down your questions as you think of them. It’s easier to collect your thoughts before your appointment than to do so during your visit.
