The Expectant Father. Armin A. BrottЧитать онлайн книгу.
she’ll have a baby with chromosomal abnormalities are roughly 1 in 190 and rise steadily as she ages. At forty, they’re about 1 in 65; at forty-five, 1 in 20.
Reasons Your Partner (or You) Might Consider Genetic Testing
• One of you has a family history of birth defects, or you know you’re a carrier for a genetic disorder such as cystic fibrosis, muscular dystrophy, or hemophilia.
• One of you is a member of a high-risk ethnic group, such as African Americans, Native Americans, Jews of Eastern European descent, Greeks, Italians, and others (see “Tests You May Have to Take,” pages 59–60).
• Your partner is thirty-five or older.
• Your partner has had several miscarriages.
• Your partner had a positive Triple (or Quad or Penta) Screen (see page 59).
• One of you might be a carrier of specific genes that have been linked with birth defects.
Other Reasons for Prenatal Testing
Prenatal testing is also available to people who, while not considered at risk, have other reasons for wanting it done. Some of the most common reasons include:
• Peace of mind. Having an amniocentesis or a Chorionic Villi Sampling (CVS) test can remove most doubts about the chromosomal health of your child. For some people, this reassurance can make the pregnancy a much more enjoyable—and less stressful—experience. If the tests do reveal problems, you and your partner will have more time to prepare yourselves for the tough decisions ahead (for more on this, see pages 71–72).
• To find out the sex of the baby (or, in some cases, to determine who the biological father is).
CHORIONIC VILLI SAMPLING (CVS)
Generally this test is performed at 9–12 weeks to detect chromosomal abnormalities and genetically inherited diseases. The test can be done by inserting a needle through the abdominal wall or by threading a catheter through the vagina and cervix into the uterus. Either way, small pieces of the chorion—a membrane with genetic makeup identical to that of the fetus—are snipped off or suctioned into a syringe and analyzed. The risks are about the same as for amnio, and the two tests can identify pretty much the same potential abnormalities. The main advantage to CVS is that it can be done a lot earlier in the pregnancy, giving you and your partner more time to consider the alternatives. That’s why the number of amnios is falling, while CVSs are rising.
Cell-Free Fetal DNA
One of the most exciting developments in prenatal testing is Cell-Free Fetal DNA (also called cfDNA or cffDNA) testing, which has the potential to eliminate the need for the vast majority of invasive diagnostics. Cell-Free Fetal DNA testing, which can be done as early as 10 weeks, analyzes tiny bits of the fetus’s DNA that are running around in the mom-to-be’s blood. According to Diana Bianchi, a pediatric geneticist at Tufts Medical Center, the results are ten times more accurate in predicting Down syndrome, and five times more accurate in predicting several other genetic conditions. The CffDNA test is nearly 100 percent accurate in ruling out problems, meaning that a negative result should relieve your anxieties. But it does produce some false positives, so a positive diagnosis would still need to be confirmed by amnio, CVS, or PUBS. Still, according to Bianchi, “Nine out of 10 women who are currently being referred for further testing would not need invasive tests.” The test is expensive, isn’t available everywhere, and may not be covered by insurance, so if you’re interested, check with your partner’s doc.
PERCUTANEOUS UMBILICAL BLOOD SAMPLING (PUBS)
No, PUBS has nothing to do with bars, although you may need one after thinking about all this. The PUBS test is usually conducted at 17–36 weeks and is sometimes ordered to confirm possible genetic and blood disorders detected through amnio or CVS. The procedure is virtually the same as an amnio, except that the needle is inserted into a blood vessel in the umbilical cord; some practitioners believe this makes the test more accurate. Later in the pregnancy, PUBS may be used to determine whether the fetus has chicken pox, Toxoplasma gondii (see page 42), or other dangerous infections. Preliminary results are available within about three days. In addition to the risk of complications or miscarriage resulting from the procedure, PUBS may also slightly increase the likelihood of premature labor or clotting of the umbilical cord, and because it can’t be performed any earlier than 17 weeks, it’s not nearly as popular as amnio or CVS.
Dealing with the Unexpected
For me, pregnancy was the proverbial emotional roller-coaster ride. One minute I’d find myself wildly excited and dreaming about the new baby, and the next I was filled with feelings of impending doom. I knew I wanted our babies, but I also knew that if I got too emotionally attached and anything unexpected happened—like an ectopic pregnancy, a miscarriage, or a birth defect—I’d be crushed. So, instead of allowing myself to enjoy the pregnancy fully, I ended up spending a lot of time torturing myself by reading and worrying about the bad things that could happen.
ECTOPIC PREGNANCY
About 1–2 percent of all embryos don’t embed in the uterus but begin to grow outside the womb, usually in the fallopian tube, which is unable to expand sufficiently to accommodate the growing fetus. Undiagnosed, an ectopic pregnancy would eventually cause the fallopian tube to burst, resulting in severe bleeding. Fortunately, the vast majority of ectopic pregnancies are caught and removed by the eighth week of pregnancy—long before they become dangerous. Unfortunately, there is no way to transplant the embryo from the fallopian tube into the uterus, so there’s no choice but to terminate the pregnancy. As quickly as technology is advancing, though, I’m sure transplantation will be possible in the not-too-distant future.
PREECLAMPSIA
This is one of the most common pregnancy complications—about 10 percent of pregnant women, most between the ages of eighteen and thirty, suffer from it, although the highest risk groups are very young teens and women in their forties. Preeclampsia is sometimes referred to as toxemia or PIH—protein-induced hypertension—because one of the symptoms is high protein in the urine. Basically, it’s an increase in the mother’s blood pressure late in the pregnancy. This can deprive the fetus of blood and other nutrients and put the mother at risk of a stroke or seizure. Women who have a history of high blood pressure or blood vessel abnormalities are especially prone, as are daughters of women who had preeclampsia when they were pregnant. And Norwegian researchers Rolv Skjærven and Lars J. Vatten found that “men born after a preeclampsia-complicated pregnancy had a moderately increased risk of fathering a preeclamptic pregnancy.” But most of the time it comes as an unpleasant surprise to everyone.
In its early stages there usually aren’t any symptoms, but it can be detected by a routine blood pressure check. If the condition worsens, the woman may develop headaches, water retention, vomiting, pain in the abdomen, blurred vision, and seizures. Interestingly, researchers now suspect that preeclampsia is actually a disorder in which the mother’s immune system rejects some of the father’s genes that are in the fetus’s cells. They suspect that women may be able to “immunize” themselves before getting pregnant if they build up a tolerance by exposing themselves to their partner’s semen as often as possible. This explains why preeclampsia is far more common during first pregnancies, or at least the first pregnancy with a new partner. It also explains why fewer women over thirty develop this condition. (Still, it can happen to older moms or those who have multiple children.)
There’s no guaranteed way to prevent preeclampsia, but there are a few things that could reduce the risk. Staying well hydrated, cutting back on salt, and getting enough exercise may help your partner keep her blood pressure under control. So can increasing her fiber intake. One study found