Month One
We'll define the first month as the six weeks following your last menstrual period, since conception occurs about two weeks into that time. What happens at the microscopic level is indeed profound, including the processes by which egg and sperm unite and there is a combining of DNA to create a new and unique individual. Almost immediately, the conception begins to produce HCG, a hormone crucial to the pregnancy. HCG triggers the ovaries to release large amounts of estrogen and progesterone, which, in turn, cause the lining of the uterus to thicken to provide nutrition to the developing embryo.

Shortly after a missed menstrual period, there are high enough hormone levels to cause the symptoms that alert you something unusual is happening. Breast soreness is most common, followed closely by frequent urination, fatigue and nausea. The majority of pregnancy tests available will turn positive by just three to four days after an expected period is late. There are, however, almost no physical changes that would be noticeable by your physician, so there's no reason to seek medical care at this stage unless you suspect a problem. It's best to schedule an office visit after a second missed period.

Nausea, unless extremely severe, does not compromise an otherwise healthy pregnancy. On the contrary, reflecting the production of a large amount of hormone, this symptom is quite reassuring and is associated with an extremely low rate of miscarriage. The hormone levels result in fragility of small blood vessels in the area of the cervix, often leading to slight spotting, which is harmless and will usually resolve on its own.

Month Two
By now, pregnancy symptoms are well established. The main physical change is uterine growth. This is often accompanied by stretching of the ligaments that hold the uterus in place. There are often quite noticeable sharp abdominal twinges, especially in a first pregnancy, as this occurs. This is not of concern, however, unless there is also bleeding.

At this point, embryonic organ formation is occurring as the cells begin the process of differentiation. For about the next six weeks, the heart, brain and all other organs start to form. You should make strenuous efforts to avoid potentially harmful influences, such as toxic fumes, alcohol and many drugs. The vast majority of substances to which you may be exposed have not been shown to be harmful, but it is extremely difficult, if not impossible, to study all these items in a scientifically sound fashion. Suffice it to say that even though we live in a society filled with auto exhaust, cigarette smoke and other waste products, the rate of fetal injury remains reassuringly low.

At a physical exam, there will be color changes, softening and uterine growth, which are relatively easy for your physician to appreciate. In addition, ultrasonography can nearly always detect the changes of a healthy fetus.

Month Three
Your hormones have reached the highest level of the entire pregnancy, will even out and soon begin a gradual decline. The good news is that nausea tends to diminish by the end of this month. Your uterus continues to grow rapidly, and you might notice that you're beginning to show. Your doctor can usually hear the fetal heartbeat, so 12 weeks is a good time to bring your partner to an office visit to hear it as well. It is remarkable how much that simple experience can bond a future father to his developing child.

You should have established pregnancy care by now, as there are new tests developing that can detect abnormalities such as Down syndrome this early. A twin pregnancy, which requires a highly specialized approach, will now be apparent.

At the 12-week (three-month) point, all organ systems are fully formed. Henceforth, only growth and maturity will occur. The risk of toxic exposure is dramatically reduced, so that drug treatments can be administered now with much less concern about effects upon the developing fetus.

Month Four
At the beginning of the fourth month, hormone levels stabilize as the unpredictable fluctuations of the first trimester give way to the development of the placenta, which provides continuous nourishment to the fetus. As the fatigue and nausea finally lift, there is a gratifying burst of physical and mental energy. You will develop improved endurance and will be encouraged to seek opportunities to engage in stretching and cardiovascular exercises, which will provide you later on with the ability to cope with the intense physical demands of the third trimester. For this reason, we refer to this segment of pregnancy as the "fitness trimester."

It is during this month that we begin screening tests to ensure proper fetal development. These may include ultrasound and blood tests so as to determine if more intensive monitoring is required, which is not usually the case. These test results should be available by the end of this month.

Month Five
By now nearly all women show, although, in the case of a first pregnancy, abdominal muscles may still be quite tight, holding the uterus in and often prompting friends to inquire whether the baby is growing adequately. Fortunately, fetal growth problems rarely occur at this stage, so there's no need to worry. Ultrasound can generally reveal anatomic details, including your baby's sex. By 20 to 21 weeks, you can expect "quickening," or fetal movement.

Stretching of the so called "round ligaments" of the uterus is quite common at this time and can result in sharp sensations in the groin areas, typically associated with sudden changes of position, such as rolling over in bed. They are not at all dangerous and will subside with rest and a warm compress to the area.

Month Six
As the second trimester comes to an end, your baby's growth is much more rapid and noticeable. You have a change in posture, as you tend to lean backward for balance. Any fitness exercises you did earlier pay off now, as there can be significant stresses to low back muscles, joints and ligaments. You might feel more uncomfortable during fitness exercises, gradually reducing their intensity and duration.

Screening for diabetes of pregnancy, which is not rare, will be carried out now. If the tests are positive, managing your diet closely can control the condition, which nearly always resolves following pregnancy.

You should start childbirth preparation classes, which will prepare you and your partner for what to expect in labor, dramatically reducing the anxiety associated with the unknown. You will most likely explore such issues as pain relief, relaxation techniques and birth alternatives. It's important not to formulate rigid birth plans as the events of labor are often dramatically different for each woman, requiring differing labor management methods.

Month Seven
A major focus this month is the monitoring of you and your baby. There seems to be an instinctual increase in self-awareness that makes pregnant women extremely sensitive to subtle changes in the activity pattern of their babies as well as their own symptoms. The fetal surveillance program referred to as "kick counting" begins now, whereby a woman spends some time each evening after dinner counting the number of minutes it takes for her baby to move ten times. For most women, this will take 20 minutes or so. If it were to take more than two hours, she would be instructed to go immediately to the hospital where monitoring would determine if a problem exists. This program continues daily until the birth. Studies have shown it to be of major value in heading off fetal problems before they even occur.

In addition, uterine contractions - which have actually been occurring throughout the pregnancy - become noticeable on a daily basis. Brief and irregular contractions, referred to as Braxton-Hicks, are normal and harmless and quite easily distinguishable from those of actual premature labor, which are long, regular and painful.

Month Eight
Reducing your activity will make you more comfortable while allowing a redirection of blood flow toward the placenta and fetus, which is needed to support the rapid growth of your baby. You should set a firm date for ending employment no later than the end of the eighth month.

Most women become aware that when they are at rest, there is a significant increase both in fetal movements and contractions. This is a positive development, which reflects the fact that resting results in the improved delivery of oxygen and nutrients to both the uterine musculature and the fetus. In addition to these benefits, rest tends to reduce maternal blood pressure and thus diminishes the risk of developing pregnancy-induced hypertension (formerly known as pre-eclampsia).

The final customary laboratory test - a culture to determine whether a pregnant woman is among the 20 percent who carry the Group B streptococcus bacteria - is carried out during this month. If a woman is positive, she will be treated during labor. This innovation of the past 20 years or so has essentially eliminated the past major problem of streptococcal infection of the newborn.

Month Nine
The stage is now set for labor and birth as contractions become stronger and more frequent. You will be seeing your ob/gyn weekly, and there will be close monitoring of your blood pressure. Exams to determine your cervical status might be started. Labor instructions will encourage timing of contractions in order to determine their length, strength and frequency. A good rule of thumb is that when you cannot carry on a conversation during a contraction, true labor is likely. A slightly bloody mucous secretion, called a "bloody show," tends to signal an impending labor, but there's no need to worry. If there are concerns about your baby's well-being, a nonstress test may be run twice a week at the hospital.

If it is decided that labor should be induced - brought on artifcially - your physician will explain the pros and cons of doing so.

Regardless of how the process of birth is carried out, the goal is to present a healthy baby to a healthy mother. It is at this momentous and life-changing event that the true benefits of all the preceding months of care become apparent. It is a time to enjoy and celebrate the miracle of life!

David M. Priver, M.D., FACOG, is a San Diego ob/gyn who has been caring for pregnant women for more than 37 years. He has delivered more than 7,000 babies.

Be the best mom and dad you can be - but cut yourselves some slack!

First-time parents bringing their newborns in for their first visit are a special group. They naturally all have different styles, but no matter how they are weathering new parenthood so far, one thing is universal: Life as they knew it has changed.

As you become acquainted with your "new life," many people will likely offer you advice. Some of it may be of no use to you, but you will no doubt embrace some advice wholeheartedly. Remember the following five points to help you through the early days at home with your little one - and beyond.

1. YOU DON'T HAVE TO BE PERFECT
You are responsible for the basics, like providing nourishment and care to your newborn. You are not required to make sure that your child has the best toy/stroller/sling on the market, or that you respond to every new challenge with the perfect solution. When it comes down to it, you don't even have to make sure that your baby's socks match. Your baby will be fine with a parent who is "good enough," especially one who realizes that perfection doesn't exist.

2. BE KIND TO YOURSELF
One analogy is that of the flight attendant explaining what to do if the cabin pressure drops. "Put your own mask on before you put one on your child." The message here is that you will not be able to take care of your child if you are not operating at your own full capacity. For example, if you are breastfeeding, remember that you need to eat and hydrate well to produce all that breast milk (nearly the amount in a wine bottle!) in a day.

Pay attention to your mood, and if you think you might be experiencing postpartum depression, get help for your own sake and for the good of your child.

3. PROTECT YOUR TIME
Now that you are a parent, your time is even more valuable a commodity than it has ever been. There are a thousand things in a day that can demand your attention, and learning to tune out things that aren't urgent will help you tremendously. For example, if the phone rings while you are spending time with your newborn - whether you're changing a diaper or having a quiet nap together - let whoever is calling leave a message.

4. ACCEPT THE HELP THAT OTHERS OFFER
Although you don't need to answer the phone every time it rings, keep in mind that sometimes it's ringing because someone wants to help you. Don't be shy about accepting offers from family and friends to come and bring you food and to do your laundry, or to watch the baby while you take a refreshing shower.

Also keep in mind that these visits are meant to be helpful, rather than overwhelming. You might want to limit how many people come by, and how long they stay. And, to prevent your baby from getting sick, make it clear that anyone who is ill should not come over.

5. TRUST YOUR DEVELOPING PARENTAL INSTINCT
New parents wonder constantly whether their newborn is behaving and developing normally. Is he sleeping too much (or too little)? Is that stool a normal consistency? With one's first newborn, the list can be endless. New parents often worry about bothering their pediatrician with these concerns, but pediatricians expect these questions. A parent's sense that something is "not right" is one of the most valuable things a pediatrician can work with, and often-serious illnesses are recognized because of a parent's instinct that something about her child is amiss.

So though you may feel unsure and need guidance in the beginning, remind yourself that you are simply cultivating your parenting instinct. In time, you will be the expert on your child.

Pregnancy expert Peter S. Heyl, M.D., responds to your questions.

Is having an ultrasound safe, or can it pose a risk to my baby?
Diagnostic ultrasound utilizes low-powered sound waves that do not harm the developing fetus. The procedure should be performed only for diagnostic purposes (that is, used as a screening test) by a sonographer credentialed by the American Registry for Diagnostic Medical Sonographers or by a physician trained and certified for this examination. You will see a certificate on the sonographer's wall, or the initials RDMS (Registered Diagnostic Medical Sonographer) on the sonographer's white jacket. Feel free to ask about credentialing beforehand as well. Be wary of a business that offers pictures or videos of your unborn baby just to add to a baby book.

I have a lower back tattoo. Will I be able to have an epidural?
The presence of a tattoo will not prevent you from having an epidural. However, anesthesiologists exercise caution. An epidural is not placed in a new tattoo that is healing, as it may cause infection. Nor is it placed directly on a tattoo, for the epidural needle may cause a scar and alter the look of the tattoo. Anesthesiologists attempt to insert the epidural needle in non-tattooed skin.

Can I deliver vaginally after having a C-section?
Currently, only one in ten women who have had a prior C-section attempt a VBAC (vaginal birth after a cesarean); 60 to 80 percent of these women who try a VBAC are successful. The decision to attempt a vaginal birth may be made with your obstetrician based on the type of incision used for your prior C-section, the complication that led to the previous C-section, whether you have had a successful previous vaginal delivery and the condition of your unborn baby. Professionals err on the side of caution when scheduling a VBAC, thinking primarily about the safety of you and your baby.

May I have just a glass of wine a day while pregnant?
Bear in mind that when an expectant mother consumes alcohol, so does her fetus. Fetal alcohol syndrome is the leading cause of preventable mental retardation in the U.S. today. For the healthy development of your growing fetus, most professionals advise avoiding all alcohol during pregnancy or when trying to conceive, since no one knows the safe amount of alcohol consumption during pregnancy.

Peter S. Heyl, M.D., practices maternal fetal medicine as an associate professor in the Department of Obstetrics and Gynecology, Eastern Virginia Medical School, Norfolk.