Assessing the Baby

Visiting the obstetrician or midwife is the only medical appointment that many people actually enjoy. Each appointment is an opportunity to appreciate that the small, day to day changes have actually wrought great progress over the course of a month. It may seem that the obstetrical appointment is little more than a social engagement, with lots of conversation and very little obstetrical practice. However, with a few simple measurements, a lot of information can be gleaned about your developing baby's health.

Your practitioner starts each visit with questions about the baby's progress, and your pediatrician will do the same in the future. Have you felt the baby move yet? Most women expecting their first baby will notice fetal movement sometime after the 16th week, possibly not until the 20th week. Many women who have already delivered a child may perceive fetal movement even earlier.

The baby is also measured indirectly by measuring the fundal height, as mentioned in Chapter 2. The measurement of fundal height, in centimeters, normally corresponds to the age of the pregnancy, measured in weeks from the last menstrual period. So if you're twenty weeks pregnant, your fundal height should be approximately 20 centimeters (cm.).

Finally, the baby is evaluated by placing a doptone on the mother's abdomen to listen for the baby's heartbeat. The doptone uses sound waves to sense the movement of the fetal heart and produces an audible beating sound that mimics the heart rate. The fetal heart rate should be between 120-160 beats per minute, although it may go higher for brief periods when the baby moves.

As you might imagine, though, the best way to assess the baby's health is to see the baby, and this can be done even before the baby is born, using ultrasound technology. Not only can the baby be measured and its weight calculated from those measurements, its internal anatomy also can be evaluated.

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Third Trimester

Pregnancy is a "low glamour" state, and at no time is this more apparent than in the third trimester (weeks 27 through 40). Everyone asks you how you feel, and you feel great, except for (choose one or more from the following list): heartburn, hemorrhoids, constipation, varicose veins, backache, difficulty sleeping, and the urge to urinate every half hour!

Most of these discomforts are the result of your baby's increasing size. But this continued growth is responsible for exciting developments as well. The fetus moves in a regular pattern each day, and many expectant women get to know their babies' characteristic movements. You need never feel alone; you always have your "buddy" with you.

Prenatal visits should become more frequent in the third trimester, increasing from once every four weeks to every other week. During the last month of pregnancy, you should visit your practitioner once a week. The increasing frequency of visits allows your doctor or midwife to monitor you and your baby more closely for some common complications of pregnancy, including pre-eclampsia (covered in Chapter 10), premature labor, and gestational diabetes.

If there are any concerns about fetal growth, your practitioner will probably order an ultrasound test (covered in the next chapter). If the fundal height is less than expected, you may not be as far along as you thought (perhaps you miscalculated the first day of your last period). If there is other evidence that confirms the gestational age (an earlier ultrasound, or previous exams that were consistent with your original due date), there is a possibility that the baby is not growing properly. An ultrasound exam can determine gestational age as well as fetal size, and thereby explain why the baby may be smaller than anticipated.

If the fundal height is greater than expected, there are other reasons why the fetal size might be greater than gestational age would indicate, including multiple pregnancy (twins, triplets or more) and polyhydramnios (excess amniotic fluid). Once again, ultrasound is the test of choice to further evaluate the discrepancy. However, it is important to remember that in most situations in which an ultrasound is ordered to evaluate fundal heights that are less than or greater than gestational age, nothing is wrong. In those cases, the discrepancy probably represents individual variation. After all, not all babies weigh the same when they are born.

As the third trimester progresses, you'll probably feel increasing excitement (and possibly a bit of apprehension) about your impending labor and delivery. The uterus offers gentle reminders in the form of Braxton-Hicks contractions. These are weak uterine contractions that generally become noticeable in the third trimester. They are normal and can be distinguished from labor contractions in a number of ways. First, they are generally very mild, causing a sensation of "tightening," without pain. Second, they do not develop any regular pattern. Third, they do not become progressively more frequent or more painful; they just go away. It's almost as if the uterus is practicing for the labor ahead.

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Second Trimester

Many women consider the second trimester (weeks 13 through 26) the best part of pregnancy. Here's why: The symptoms of the first few months have largely abated, and the discomforts of the last trimester have not yet started.

Now your pregnancy is visible for all the world to see! If you have not already started to wear maternity clothes, you'll likely need them now. Each week your developing baby-now officially a fetus-grows a bit more. Your practitioner will measure fetal growth at your prenatal visits, albeit indirectly. He or she will use a tape measure to determine the distance from your pubic bone to the top of the uterus (also known as the fundus). This measurement is known as the fundal height.

During the second trimester, the mother first notices fetal movement, generally some time between 16-20 weeks. However, reflexive movements begin during the embryonic period, and the fetus becomes active before the mother notices. Early in pregnancy, the fetal movements are relatively weak, and there is a greater amount of room available for movement. Therefore, it is unlikely that the fetus will bang up against the uterine wall with enough force for Mom to notice.
Experienced mothers remember the first flutterings from previous pregnancies and are more attuned to even the weakest movements. That's why they are more likely to notice fetal movement earlier. Later in pregnancy, the fetus is much stronger and relatively more confined. In fact, fetal movements become so vigorous they can be observed through the mother's abdominal wall. They have been known to keep expectant mothers up half the night-and expectant fathers, too, if the parents-to-be sleep too close together!

Vital organs continue to mature throughout the second trimester. Babies born before approximately 24 weeks are considered pre-viable (too young to survive). That's because their lungs are not sufficiently developed to exchange oxygen. The lungs gradually begin to acquire this critical capacity during the last several weeks of the second trimester. However, with appropriate support in a neonatal intensive care unit, most babies born after 26 weeks can survive. Babies born at this early age may weigh as little as two pounds and may have extremely serious medical problems.

The development of the external genitalia is completed early in the second trimester, and the baby's sex can usually be recognized by ultrasound at the same time that it is safe to perform amniocentesis. In females, the fetal ovary undergoes significant development during the second trimester. Remarkably, all the ova that the ovaries will ever contain are formed by the fifth month of fetal life! After their formation, the ova enter a state of rest in which they will remain until puberty. Nature prepares for the next generation even before the new generation is born!
Several important prenatal tests are administered during the second trimester. These include ultrasound, serum alphafetoprotein assay (AFP), and, possibly, amniocentesis.

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