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Week 13
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How Big Is Your Baby?

Your baby is growing rapidly! Its crown-to-rump length is 2.6 to 3.1 inches (65 to 78mm), and it weighs between 0.5 and 0.7 ounce (13 to 20g). It is about the size of a peach.

How Big Are You?

Your uterus has grown quite a bit. You can probably feel its upper edge above the pubic bone in the lowest part of your abdomen, about 4 inches (10cm) below your bellybutton. At 12 to 13 weeks, your uterus fills your pelvis and starts growing upward into your abdomen. It feels like a soft, smooth ball.

You have probably gained some weight by now. If morning sickness has been a problem and you've had a hard time eating, you may not have gained much weight. As you feel better and as your baby rapidly starts to gain weight, you'll gain weight.

How Your Baby Is Growing and Developing

Fetal growth is particularly striking from now through about 24 weeks of pregnancy. The baby has doubled in length since the 7th week. Changes in fetal weight have also been tremendous during the last 8 to 10 weeks of your pregnancy.

One interesting change is the relative slowdown in the growth of your baby's head compared to the rest of its body. In week 13, the head is about half the crown-to-rump length. By week 21, the head is about one-third of the baby's body. At birth, your baby's head is only one-fourth the size of its body. Fetal body growth accelerates as fetal head growth slows.

Your baby's face is beginning to look more humanlike. Eyes, which started out on the side of the head, move closer together on the face. The ears come to lie in their normal position on the sides of the head.

External genitalia have developed enough so a male can be distinguished from a female if examined outside the womb.

Intestines initially develop within a large swelling in the umbilical cord outside the fetal body. About this time, they withdraw into the fetal abdominal cavity. If this doesn't occur and the intestines remain outside the fetal abdomen at birth, a condition called an omphalocele occurs. It is rare (occurs in 1 of 10,000 births). The condition can usually be repaired with surgery, and babies do well afterward.

Changes in You

You are losing your waist! Clothing fits snugly. It's time to start wearing loose-fitting clothing.

Stretch Marks

Stretch marks, called striae distensae, are seen often and in varying degrees during pregnancy. They may appear early in your pregnancy, usually on the abdomen, breasts, and hips or buttocks. After pregnancy, they may fade to the same color as the rest of your skin, but they won't go away.

Hillary was concerned about stretch marks that had begun to appear on her abdomen and breasts. She wanted to know what to do about them. I told her there is no known prevention or cure for stretch marks. Women have tried many kinds of lotions with ingredients ranging from lanolin to aloe vera to mineral oil. It doesn't hurt to try lotions, but it probably won't make much difference.

If you use steroid creams, such as hydrocortisone or topicort, to treat stretch marks during pregnancy, you absorb some of the steroid into your system. The substance can then pass to your developing baby. Don't use steroid creams during pregnancy without first checking with your doctor. (See Week 26 for additional information.)

Changes in Your Breasts

You have probably noticed your breasts are changing. See the illustration on page 118. The mammary gland (another name for the breast) got its name from the Latin term for breastùmamma.

Your breast is made up of glands, connective tissue to provide support and fatty tissue to provide protection. Milk-producing sacs connect with the ducts leading to the nipple.

Before pregnancy, the average breast weighs about 7 ounces (200g). During pregnancy, breasts increase in size and weight. Near the end of pregnancy, each breast may weigh 14 to

28 ounces (400 to 800g). During nursing, each breast may weigh 28 ounces (800g) or more!

Size and shape of women's breasts vary greatly. Breast tissue usually projects under the arm. Glands that make up the breast open into ducts in the nipple. Each nipple contains nerve endings, muscle fibers, sebaceous glands, sweat glands and about 20 milk ducts.

The nipple is surrounded by the areola, a circular, pigmented area. Before pregnancy, the areola is usually pink. It turns brown or red-brown and enlarges during pregnancy and lactation. A darkened areola may act as a visual signal for the breastfeeding infant.

Breasts undergo many changes during pregnancy. In the early weeks, a common symptom of pregnancy is tingling or soreness of the breasts. After about 8 weeks of pregnancy, your breasts may grow larger and become nodular or lumpy as glands and ducts inside the breasts grow and develop. As your breasts change during pregnancy, you may notice veins appear just beneath the skin.

During the second trimester, a thin yellow fluid called colostrum begins to form. It can sometimes be expressed from the nipple by gentle massage. If your breasts have grown, you may notice stretch marks on your breasts similar to those on your abdomen.

Mammary glands begin to develop in the 6-week-old embryo. By the time of birth, milk ducts are present. After birth, a newborn's breasts may be swollen and may even secrete a small amount of milk. This can occur in both male and female infants and is caused by the secretion of estrogen.

How Your Actions Affect Your Baby's Development

Working during Pregnancy

Today, many women work outside the home, and many continue to work during pregnancy. It is common for employers and patients to ask doctors about work and pregnancy.

ôIs it safe to work while I'm pregnant?ö

ôCan I work my entire pregnancy?ö

ôAm I in danger of harming my baby if I work?ö

More than half of all women work or are seeking work. In the United States, more than 1-million babies are born to women who have been employed at some time during pregnancy. These women have understandable concerns about safety and occupational health.

Legislation that May Affect You

The U.S. Pregnancy Discrimination Act prohibits job discrimination on the basis of pregnancy or childbirth. It states pregnancy and related conditions should be treated the same as any other disability or medical condition. A doctor may be asked to certify a pregnant woman can work without endangering herself or her pregnancy. Pregnancy-related disability comes from:

ò the pregnancy itself

ò complications of pregnancy, such as pre-eclampsia,

premature labor or other medical problems

ò job exposures to chemicals, inhalants, gases, solvents or radiation

The Family and Medical Leave Act was passed in 1993. If you or your husband have spent at least 1 year working for a company, the law allows each of you to take up to 12 weeks of unpaid leave in any 12-month period for the birth of your baby. Leave may be taken intermittently or all at once.

Under the law, you must be restored to an equivalent position with equal benefits when you return. However, the act applies only to companies that employ 50 or more people within a 75-mile radius. States may allow an employer to deny job restoration to those in the top 10% compensation bracket.

At this time, about half the states have passed state legislation that deals with parental leave. Some states provide disability insurance if you have to leave work because of pregnancy or birth.

In Canada, unpaid parental leave is available. The length of time you may take off from work varies from province to province.

Risks If You Work during Pregnancy

It may be difficult to know the exact risk of a particular job. In most cases, we don't have enough information to know all the specific substances that can harm a developing baby.

The goal is to minimize the risk to the mother and baby while still enabling the woman to work. A normal woman with a normal job should be able to work throughout her pregnancy. However, she may need to modify or to change her job somewhat. For example, she may need to spend less time standing. Studies show that women who stand in the same position for prolonged periods are more likely to give birth to premature babies and babies with low birth weight.

Work with your doctor and your employer. If problems arise, such as premature labor or bleeding, listen to your doctor. If bed rest at home is suggested, follow your doctor's advice. As your pregnancy progresses, you may have to work fewer hours or do lighter work. Be flexible. It doesn't help you or your baby if you ôwear yourself outö and make complications of pregnancy worse.

You Should also Know

Caffeine Use during Pregnancy?

Caffeine is a central-nervous-system stimulant found in many beverages and foods, including coffee, tea, cola drinks and chocolate. It is also found in some medications, particularly diet aids and headache medications. To date, no benefits to you or your unborn baby have been found with the use of caffeine.

As little as 4 cups of coffee (800mg of caffeine) a day have been associated with a decreased birth weight and a smaller head size in newborns. Some researchers believe there is an association between caffeine use and miscarriage or premature labor.

Caffeine crosses the placenta to the baby. It can affect calcium metabolism of the mother and the baby. Your caffeine consumption may also increase the chances of breathing problems in your newborn. Caffeine passes to breast milk, which can cause irritability and sleeplessness in a breastfed baby. An infant metabolizes caffeine slower than an adult, and caffeine can collect in the infant.

Effects of caffeine on you during pregnancy may include irritability, sleeplessness and jitters. Smoking may compound the stimulant effect of caffeine.

Limit the amount of caffeine you consume. Read labels on over-the-counter medications for caffeine. Eliminate as much as you can from your diet. It's healthy for your baby, and you'll probably feel better, too.

Nursing with Silicone Breast Implants

Women have nursed with breast implants. Implants may make it more difficult to nurse. Doctors don't agree as to whether it is safe or possibly harmful to nurse with implants. If you are concerned, discuss the matter with your doctor; ask him or her for the latest information.

Silicone Breast Disease

Research continues into silicone breast implants and how they affect women. In 1995, the American College of Rheumatology issued a statement that there was no demonstrable risk between silicone breast implants and connective-tissue diseases or rheumatic disease. In contrast, other studies have shown a small but significant risk of developing a connective-tissue disorder with silicone breast implants.

Some labs in the U.S. offer diagnostic tests to screen for silicone breast disease. However, none of these tests have been approved by the Food and Drug Administration. Check with your physician if you are concerned.

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