PROCEDURES
ULTRASOUND (SONOGRAM)
This noninvasive test is painless to the mother, safe for the baby, and can be performed any time after the fifth week of pregnancy. By bouncing sound waves around the uterus and off the fetus, ultrasounds produce a picture of the baby and the placenta. To the untrained eye, standard, 2-D images look remarkably like Mr. Potato Head, without the glasses and mustache. 3-D ultrasounds generate a more complete image of the fetus. And 4-D ultrasounds (sometimes called dynamic 3-D) actually let you see your future baby in action, sucking his thumb, napping, swimming, and doing whatever else fetuses do to pass the time.
In the first trimester, your doctor will probably recommend an ultrasound only if there’s something going on that’s a little out of the ordinary. The most common reason is that the size of the uterus doesn’t correspond to the age of the fetus when measured from your partner’s last period. The doc may also order an ultrasound if your partner has experienced any bleeding, if there’s any doubt as to the number of fetuses, or if he or she suspects an ectopic pregnancy (a pregnancy that takes place outside the uterus). At this stage, the ultrasound can confirm that there’s a heartbeat and can measure the baby (starting with the charmingly named Crown-Rump Length, which will give you a better due date estimate).
Depending on your partner’s risk, her doctor may offer or recommend a nuchal translucency ultrasound (NT scan), a special type of ultrasound that measures fluid in the nuchal fold, a spot at the base of your baby’s head. Excess fluid in that area is often associated with chromosomal abnormalities and some heart conditions. The test needs to be done between 11 and 14 weeks and is usually part of what’s called the combined first trimester screening, which includes a blood test measuring your partner’s levels of pregnancy associated plasma protein A (PAPP-A) and a hormone called hCG. The combined test is about 85 percent accurate and has a false-positive rate of 5 percent.
There’s also an integrated screening, which uses the results of the combined screening and adds in the Quad test I describe below, which is done between 15 and 20 weeks. Taken together, this increases the detection rate and reduces the false-positive rate to about 1 percent.
Second-trimester ultrasounds are usually the ones that low-risk couples see first. They’re used to determine the sex of the baby (this one is optional), to get a more accurate estimate of the due date, or just because you’re curious about what the baby looks like. If this is the first ultrasound, your practitioner will want to confirm the number of residents in the uterus, see how well they’re moving around, and make sure all the body parts and organs are the right size and in the right place. The test may also be used to firm up the due date and to confirm anything that may have come up in other prenatal testing, including the Triple or Quad Screen, amniocentesis, and CVS (see pages 61–62).
During the last part of the pregnancy—and especially if the baby is overdue—your partner’s doctor may order additional ultrasounds to determine the baby’s position, to make sure the placenta is still functioning, or to confirm that there’s still enough amniotic fluid left to support the baby.
TRIPLE OR QUADRUPLE SCREENS
The Triple Screen measures three chemicals that may show up in your partner’s blood: AFP (Alpha-Fetoprotein), hCG (human chorionic gonadotropin), and estriol. The Quad adds one more substance, Inhibin A, to the screen, and there’s actually a Penta, which includes yet another substance, ITA (Invasive Trophoblast Antigen). Together they’re used to flag potential abdominal wall abnormalities and a variety of neural-tube defects (defects relating to the brain or spinal column), the most common of which are spina bifida and anencephaly (a completely or partially missing brain). Whether you have the Triple, the Quad, or the Penta (is this is sounding like Olympic gymnastics judging, or is it just me?) will depend on what your doctor orders. Theoretically, the more things you test for, the lower the false-positive rate.
These simple blood tests are conducted when your partner is 15–20 weeks pregnant, and the results are usually available within a week, sometimes even the next day. It’s important to understand that a “positive” result is not necessarily an indication of the presence of an abnormality, just that there might be a problem. Most turn out perfectly fine, but if your partner does get a positive result, she’ll be asked to take additional tests, such as an ultrasound and amniocentesis, which should clear up any doubts you have. Since these screens are really designed to let your partner know whether she needs additional testing, she may not want to bother if she’s planning to have an amnio or an in-depth ultrasound test.
TESTS YOU MAY HAVE TO TAKE
No, you’re not pregnant, but there are still a few times when you may need to give a little blood to make sure all is well with your baby. A variety of genetically transmitted birth defects, for example, affect some ethnic groups more than others. So, based on your family histories, your partner’s doctor may order one or both of you to get additional blood tests. OB Saul Weinreb told me that “every person in the world is estimated to carry thousands of potentially harmful genetic mutations, which means that every couple has an approximately equal chance of having a baby with a random genetic disease they had no idea they carried.” The good news is that science has been able to identify certain diseases that occur more commonly in certain ethnic groups. So rather than think of these groups as somehow genetically worse off than others, think of them as being lucky that there are tests for conditions that may affect them. New tests are being developed every day. Among the most commonly identifiable conditions are:
• Sickle-cell anemia. If you’re African American or if your family came from the Caribbean, Italy, Sardinia, or India, you may want to be tested whether your practitioner suggests it or not. If your partner knows she’s negative, though, ask the doctor whether you should bother.
• Tay-Sachs and Canavan Disease. If either you or your partner is of Ashkenazi (Eastern European) descent, get tested. Tay-Sachs is also found in some non-Jewish French Canadians. Interestingly, once your partner is pregnant, it is more accurate to test you for these conditions than to test her. If your results come back positive, she’ll need to be tested, though.
• Cystic fibrosis. The American College of Obstetricians and Gynecologists now recommends that OBs offer cystic fibrosis testing routinely.
• Thalassemia. Affects mainly families of Asian, Southeast Asian, African, Middle Eastern, Greek, or Italian origins.
You may also have to be tested if your partner has a negative Rh (for rhesus, like the monkey) factor in her blood. If you’re positive (and most of us are), your baby might be positive as well. If this is the case, your partner’s immune system might think the Rh-positive baby is some kind of intruder and try to fight it. This can lead to fetal brain damage or even death. Fortunately, this problem is preventable: your partner will have to get some anti-Rh injections, starting around the 28th week of the pregnancy.
INVASIVE PROCEDURES
AMNIOCENTESIS
This extremely accurate test is usually performed at 15–18 weeks, and can identify nearly every possible chromosomal disorder, including Down syndrome. It can’t, however, detect deformities such as cleft palate. If your baby is at risk of any other genetic conditions, your partner’s doctor can order additional testing (but these tests are not done routinely). Amnio is also sometimes used in the third trimester of pregnancy to help doctors determine whether the fetus’s lungs are mature enough to survive an emergency premature delivery, if they’re worried about that. The test involves inserting a needle through the abdominal wall into the amniotic sac, where about an ounce of fluid is collected and analyzed. Results are usually available in one to three weeks. Unless your partner is considered at high risk (see page 61), or either of you needs to be reassured that your baby is healthy, there’s no real reason to have this test. The chances that a twenty-five-year-old woman will give birth to a baby with a defect that an amnio can detect are about 1 in 500. The chances that the procedure will cause a miscarriage,