Your Guide to Becoming a Mother

Get your baby off to a safe start.


In the span of just 38 weeks, your baby grows from a miniscule group of cells that could fit on the head of a pin to an infant who weighs an average of 7 1/2 pounds and possesses every physical feature he needs to live outside your body. It’s an amazing transformation, and one you probably wish you could watch. In this last installment of our three-part series, you’ll find the next best thing: a conception-to-newborn look at your baby and tips on making his very first home a safe, healthy place to grow and develop.

Get your baby off to a safe start

Don’t wait for a positive pregnancy test or your first visit to the obstetrician to clean up your act. “By the time of your first prenatal exam, all the baby’s major organs have started to form,” says Siobhan M. Dolan, M.D., assistant medical director of the March of Dimes. Here’s what you need to do:

Schedule a preconception visit with your obstetrician or midwife. Talk about getting your immunizations up to date, clearing up any existing infections, reviewing your medications and getting genetic counseling if indicated. Have your blood sugar checked, too: Very high levels put a baby at risk for heart and neural-tube defects.

Begin taking folic acid supplements (400 micrograms daily) at least one month before trying to conceive.

Don’t smoke cigarettes or use recreational drugs. Alcohol—in any amount—is also off limits throughout pregnancy.

Avoid contact with cat feces, which can transmit toxoplasmosis, a dangerous infection.

Don’t take any herbal remedies or over-the-counter medications without your doctor’s knowledge.

Stay out of hot tubs and saunas, and don’t get overheated during exercise.

Don’t eat raw meat or fish, unpasteurized cheeses or other foods that can harbor dangerous bacteria, such as listeria.

Protect yourself against infections, including chickenpox and sexually transmitted diseases.

Stay away from harmful chemicals, pesticides, solvents, lead and mercury, as well as medically unnecessary X-rays.

From Conception to Birth: A TIMELINE

The ages in this timeline refer to the age of the embryo or fetus, not the length of the pregnancy (40 weeks from the first day of your last period). Example: When your embryo is 6 weeks old, you are in the 8th week of pregnancy.

1 week

Size>>Smaller than the head of a pin

Looks like>>A cluster of cells

What’s going on>>Zygote is traveling through the fallopian tube to implant itself in the uterus.

2 weeks

Size>>About 1 millimeter long (slightly larger than a pinhead)

Looks like>>A cluster of cells

What’s going on>>The blastocyst is attached to uterine lining and starting to sort itself out into different layers.

3 weeks

Size>>Approximately 1.25 millimeters long (about the size of a small sesame seed) Looks like>>An even larger cluster of cells What’s going on>>Embryo’s heart, brain, spinal cord, muscles and skeleton are beginning to form.

4 weeks

Size>>2–4 millimeters long (about the size of a large sesame seed) Looks like>>A tadpole, complete with a head and tail What’s going on>>Brain and spinal cord develop; eyes and limbs begin to form; heart begins beating.

5 weeks

Size>>1/2 inch long (crown to rump; about the size of a raisin) Looks like>>A tadpole with thick arm and leg buds What’s going on>>Arms, legs, hands and feet continue to develop; heart divides into two chambers; air passages form in lungs; eyes are forming.

6 weeks

Size>>1/2–3/4 inch long (approximately the size of a pinto bean) Looks like>>a tadpole with longer arms and legs; eyes, nose and ears begin to show What’s going on>>Fingers and toes develop; embryo starts to move.

7 weeks

Size>>1–11/2 inches long (about the size of an olive) Looks like>>Eyes, nose, mouth, fingers, toes and ears are clearly visible. What’s going on>>Head, neck, fingers, toes and outer ears developing; movement can be seen on ultrasound.

8 weeks

Size>>11/4–13/4 inches long; weighs about 5 grams (about 1/5 oz.); about the size of a walnut Looks like>>Resembles a baby more, with a large head and recognizable features. What’s going on>>Most organ systems growing quickly; reproductive tract yet to form.

9 weeks

Size>>1 1/2–2 1/2 inches long; about 8 grams (roughly the size of a large lime)

Looks like>>Head still

disproportionately large, but limbs are catching up.

What’s going on>>Head stretches upward from chest; neck lengthens; fingernails

and external genitals begin

to appear.

10 weeks

Size>>2 1/2 inches long;

about 8–14 grams (about the size of a small lemon)

Looks like>>Body size begins to catch up with head.

What’s going on>>Most

of the body is formed; hair starts to grow; genitals begin to look male or female; fetus can squint, open mouth, move fingers and toes.

11 weeks

Size>>2 1/2–3 inches long; weighs 13–20 grams (under 1 oz.; about the size of a tennis ball)

Looks like>>Face continues to look more humanlike; external genitals have distinct male or female form.

What’s going on>>All systems and organs continue to grow and develop; genitals distinctly male or female.

12 weeks

Size>>3 1/2–4 inches long (about the size of a baseball); weighs almost 1 oz.

Looks like>>Ears and eyes have moved to their final positions.

What’s going on>> All systems and organs continue to grow and develop; cartilage being transformed into bone.

13-14 weeks

Size>>4–4 1/2 inches long; 1 3/4–2 3/4 oz. (about the size of a softball)

Looks like>>Blood vessels are visible through skin; fine hair (lanugo) covers body.

What’s going on>>Bones are hardening; fetus can smell, taste and swallow; may suck its thumb.

17-19 weeks

Size>>5 1/4–7 1/4 inches long;

7–10 1/2 ounces (about the

size of a large banana)

Looks like>>Fetus begins

to put on fat.

What’s going on>>Fetus begins swallowing more

amniotic fluid, which helps digestive system develop;

is able to hear; pregnancy is half over.

23-25 weeks

Size>>8 3/4–10 3/4 inches long;

1 1/2–3 pounds (about the size of a cantaloupe)

Looks like>>Eyebrows, eyelashes and hair on head are present; fetus looks plumper.

What’s going on>>Has sleep/wake cycles; if born now, has a chance of surviving; at about 24 weeks, appears

to recognize parents’ voices.

29-33 weeks

Size>>11 3/4–13 1/4 inches long (20 1/4 inches including legs); 3 1/2–5 1/2 pounds (about the size of a basketball)

Looks like>>Fetus is chubbier, more babylike.

What’s going on>>Fetus makes purposeful movements to get comfortable; lungs (among last organs to develop fully) continue maturing.

34-38 weeks

Size>>20 3/4–21 1/2 inches long; 6–7 1/2 pounds (about the size of a medium watermelon!)

Looks like>>Fetus is bigger and very newborn-like.

What’s going on>>In 97 percent of pregnancies, fetus begins to move into delivery position; by week 37, lungs

are developed; by week 38,

is ready to be born.

A GLOSSARY of terms Zygote stage: the first week after fertilization Blastocyst stage: weeks 1–2 after fertilization Embryonic stage: weeks 2–8 after fertilization Fetal stage: weeks 9–38


Here’s what kind of action to expect from within, and when:

((First heartbeat)) Your baby’s heart starts beating a few weeks after conception, but you’ll have to wait until about the 12th week of pregnancy to hear it.

((First kicks, aka quickening)) You’ll feel these anywhere from 16 to 20 weeks of pregnancy, depending on the fetus’ size, activity level and other factors.

((First look)) If you have an uncomplicated pregnancy, chances are you’ll have your first (and, perhaps, only) ultrasound at about 18 weeks. At that point, the baby’s gender usually can be determined; certain birth defects, including Down syndrome and spina bifida, also may be detected. The due date can be fine-tuned, and the doctor can determine whether it is a multiple pregnancy and check on the health of the placenta and the fetus’s organs. ((First hiccups)) Anytime from about 20 weeks on, you may notice little popping feelings in your abdomen when the fetus has hiccups. Some have a lot; others have none.

((First step toward the exit, aka “dropping” or “lightening”)) Some babies move lower in the mother’s pelvis a few weeks before delivery, some just as labor starts and some not at all. When this happens, you may experience less indigestion and find it easier to breathe, but you may also feel more pressure on your bladder and rectum.

Meet the newborn

>>Just after birth, your baby undergoes a series of procedures to test and protect his health. First, the umbilical cord is clamped and cut, and the baby’s mouth is suctioned to reduce the chance that he will inhale fluids. Then, nurses administer the Apgar test twice—at one and five minutes after delivery. The baby receives a score of , 1 or 2 in five areas: heart rate, breathing, muscle tone, reflexes and color. Most babies receive total scores of 7, 8 or 9 after a normal, healthy delivery; those with low scores may need treatment such as resuscitation or require time in the intensive-care unit. Your baby will also receive a vitamin K injection, which helps with blood clotting, as well as antibiotic eye drops. A few drops of his blood will be taken, and his hearing will be tested before he goes home. In a day or two (three or four, if you’ve had a Cesarean), you’ll be sent home with your newborn. Here’s the poop on, well, his poop and other things to expect.

The poop>> Black, tarry- looking stools are normal for a few days, then change to watery, mustardy ones (for breastfed babies). They occur anywhere from once to several times a day. What to watch for: If your baby doesn’t poop, is very gassy, pushes noticeably to pass a stool or pulls up his legs and cries, call your pediatrician.

The diapers>> By the time you leave the hospital, your baby should have wet diapers about 12 times a day. What to watch for: Too few wet diapers could indicate that the baby isn’t getting enough breast milk or formula or has a urinary-tract problem.

The cord stump>> It’s normal for the umbilical cord stump to ooze and turn black before falling off a week or two after birth. Most pediatricians recommend cleaning it with rubbing alcohol after each diaper change. What to watch for: Redness, pus, tenderness or fever could indicate an infection; call your pediatrician. Note: Look out for the same symptoms at your baby’s circumcision site, if applicable.

The skin>> It’s not unusual for newborns to develop a touch of jaundice. This occurs when the blood contains too much bilirubin, a chemical formed when red blood cells break down. What to watch for: Call your pediatrician if you notice that your baby has yellowish skin (it usually appears first on the baby’s face).

The digestive system>> Spitting up a bit after feeding usually is normal. What to watch for: Forceful vomiting or spitting up most or all of a feeding.

Newborn Screening

>>Shortly after delivery, a nurse will take a small amount of blood from your baby’s heel for testing. “Thirty diseases can be ruled out with just a few drops of blood taken after birth,” says Jonathan Muraskas, M.D., a professor of neonatal-prenatal medicine at Loyola University Medical Center in Maywood, Ill. In some cases, such blood tests can catch conditions that, if corrected right away, can prevent serious problems in your baby’s future. For example, if tests show that a baby has congenital hypothyroidism, medication can prevent severe mental retardation.

Unfortunately, not all states require extensive newborn screening, according to the March of Dimes. All states screen newborns for phenylketonuria (PKU), a disorder that can cause brain damage and mental retardation if undetected. But only about 30 states currently screen for biotinidase deficiency, an enzyme deficiency that can lead to infections, hearing loss, mental retardation and death. For an updated list of what your state mandates, check out the National Newborn Screening & Genetics Resource Center at

The March of Dimes urges all states to test for 10 treatable disorders. Check with your obstetrician or pediatrician to see what screening tests your baby will receive and whether additional ones would make sense. Private companies such as Pediatrix Screening ( screen for 45 to 61 disorders, at a cost of $25 to $70, depending on the number of tests requested. Check with your health insurance carrier to determine whether non-mandated tests are covered.