What You Should Know About Pregnancy
The sound of my 10-week-old baby-to-be's heartbeat filled the room, caroming off the walls, as percussive as a marching band. The nurse practitioner who'd strapped the fetal monitor to my belly smiled. "Wow, that child is already so strong," she said. "The next few months of your life are going to be very interesting." I didn't pay much attention. I was too enraptured with this raucous new life sparking inside me Ã¢â‚¬” the first science project I had ever, to my knowledge, performed correctly. But I soon discovered the truth in my nurse's veiled warning. The next 6 months were plenty interesting. I experienced elation, despair, indigestion, fluctuating blood sugar, and a mad craving for pineapple juice Ã¢â‚¬” not to mention the vomiting. It was the loveliest and most disagreeable time of my life.
Pregnancy can make a woman glow. But it also can give her acne and make her sick, exhausted, crabby, or worse. It's distressingly common for pregnant women to develop severe conditions such as high blood pressure or diabetes, resulting in some 10 million injuries and 529,000 deaths worldwide annually, according to the World Health Organization. Gestation and labor are, frankly, hard work Ã¢â‚¬” which is perhaps why nature saw fit to apportion the task to females.
In the mid-19th century, most doctors believed that human babies came ready-made Ã¢â‚¬” that every human egg contained a tiny infant that, like a sea monkey, would unfold and grow when exposed to the right ingredients. Of course, back then people also thought raw meat spawned maggots through spontaneous generation. Thankfully, our understanding of reproduction has progressed a bit. The union of a woman's egg and a man's sperm, each containing only one DNA strand, produces a human embryo. The two strands join and the resulting cell, called a zygote, possesses a full set of genes, half from each parent. The zygote divides into two cells, then four, then eight, and so on, until the full-fledged embryo burrows into the womb.
Doctors used to take a Hallmark view of pregnancy. They considered it a harmonious process, with the baby as the passive recipient of gentle nurturing from Mom. Today, emerging facts about fetal genetics reveal that baby-making is actually a rather harsh contest. It's a battle between the agendas of the fetus, its mother, and Ã¢â‚¬” not to be forgotten Ã¢â‚¬” the father, whose genes are also in there, squabbling and scheming away. "Pregnancy may be the most intimate relationship in all of nature," says evolutionary biologist David Haig, Ph.D., of Harvard University. "But it is not one body, one flesh." All the issues, in fact, that keep family therapists in business Ã¢â‚¬” greed, selfishness, misunderstandings, furtive alliances Ã¢â‚¬” start at conception.
Remember Alien? Okay, it's a stretch, but not as big a one as we might like to think. Every pregnancy brings together two beings, with different DNA, who must share a single body for 9 months. Practically from day one, the fetus sends damaging substances into its mother in an effort to increase its own nutrition and blood supply. The mom protects herself by shutting down some of the fetus's more assertive genes Ã¢â‚¬” akind of genetic time-out Ã¢â‚¬” and by releasing proteins that help her hoard nutrients. This struggle spawns many of the complications of pregnancy Ã¢â‚¬” from morning sickness to more severe conditions like high blood pressure. The mother's genes want a healthy baby, but they also want her to stay fit enough to have more children. The baby's genes couldn't care less about brothers and sisters. They say: Gimme gimme gimme. It's a mix, Dr. Haig says, "of cooperation and exploitation."
But there's good news in all this for anyone who's considering joining the baby-making fray. Research is pointing the way to better diagnostic tests for monitoring the health of mother and child. And knowledge is power. The more you know about what's going on in your body during the prizefight that is pregnancy, the better equipped you'll be to make sure no one comes out a loser.
[Round 1] Mom vs. Dad
No matter how well meaning any particular father is, from an evolutionary perspective, dads are faithless hounds. Homo sapiens was not designed for monogamy. The genes a father bestows on his offspring have different ambitions from those contributed by the mother. Dad's genes aren't overly concerned with the welfare of his current flame, since he may hook up with a different female down the road. (Mom might stray as well, but her genes will always work in her best interests.)
You can see a father's selfish genes at work in baby fat. Most mammals come into the world as skin and bones and quickly put on padding afterward. A flying squirrel weighs a tenth of an ounce at birth, just 2 percent of its adult heft. Human babies, by contrast, can grow to a roly-poly 10 pounds in the womb Ã¢â‚¬” 6percent or more of their adult weight. Those pounds of flesh come directly from the mother Ã¢â‚¬” and in addition to providing the nutrition to produce that fat, she has to go through the hardship of squeezing such a plump baby out. "There's not much evolutionary sense to the size of human babies," Dr. Haig says.
Not for Mom, maybe, but how about for the guy who only has to attend Lamaze classes and strap in the car seat? A bigger baby is a healthier baby, a man's genes reason. (Genes don't really think, of course, but they survive when they're successful, which makes them seem purposeful.) Male mice Ã¢â‚¬” and likely male humans as well Ã¢â‚¬” give their babies a gene that tells the fetus to pack on pounds. Mom fights back by, apparently, shutting off her copy of that gene and instead contributing a different one that tries to keep fetuses small. Dad, predictably, shuts down his version of that gene. But Mom's don't-grow-big message isn't as strong as Dad's eat-up encouragement, so the result is that chubby newborn. It's a sort of precustody battle, with the ultimate victor being the fetus.
[Round 2 ] Mom vs. Fetus
You wouldn't hand your teenager your purse. But scientists are discovering that a developing tot is already busy rifling through its mom's bodily resources. For starters, it restructures its mother's circulatory system Ã¢â‚¬” consider it a sort of ad hoc engineering project. Early in pregnancy, the tiny embryo sends out grasping, tendril-like cells called trophoblasts that clamp it to the uterine wall. These cells then go to work on the mother's blood vessels. They widen her arteries and thin her arteries' walls to speed food delivery to the baby through the placenta.
Meanwhile, the mother's body tamps down its immune system to keep it from attacking what is essentially foreign tissue. That's why pregnant women are more susceptible to colds and the flu Ã¢â‚¬” not to mention the blotchy, reptilian-looking rash that sprouted on my upper arms. As if that's not enough self-sacrifice, the fetus sends proteins into Mom's bloodstream to ensure she won't eat (or keep down) foods like coffee and alcohol that might harm it. You got it: Morning sickness, which afflicts up to 85 percent of pregnant women, is brought to you by Junior.
That's why nausea is worst in early pregnancy, when a fetus's fragile organs are developing, according to a recent study by biologist Paul Sherman, Ph.D., of Cornell University, and his then graduate student Samuel Flaxman. In addition, nausea is notably rare in pregnancies that end in miscarriage. It takes a healthy fetus to make a mom truly miserable.
From there it just gets worse. The placenta pumps proteins into Mom to make her body resistant to insulin, raising her blood sugar levels and providing a banquet for baby. Most women compensate by making more insulin, but some can't. These women end up with gestational diabetes, which occurs in about 4 percent of all pregnancies. Although the condition goes away once the woman gives birth, it can make her 20 to 50 percent more likely to develop diabetes in the future. Thanks a lot, kid. Your doctor will monitor your blood sugar during pregnancy and, if a problem arises, will treat it by adjusting your diet (no sweets!) or, in the worst cases, prescribing insulin shots.
Another 5 percent of pregnant women develop dangerously high blood pressure, a condition known as preeclampsia. The placenta, the baby's lifeline, has low blood pressure and relies on the naturally higher blood pressure of the mother's body to pump in nutrients. If Mom's blood pressure can be made to rise even more, all the better: The fetus will get an even greater share. The placenta achieves this goal by producing a protein called sFlt1, which makes it difficult for a woman's body to repair old blood vessels and create new ones, according to new research by Ananth Karumanchi, M.D., a kidney specialist at Harvard Medical School. Women have 4 pounds of extra blood circulating during pregnancy, and they need those additional blood vessels to carry it. If they can't build them, their blood pressure will rise.
Most pregnant women respond to this unwelcome sFlt1 invasion by making a protein that promotes blood vessel growth, which soon stabilizes the pressure. But women who are obese, who already had high blood pressure, or who have some still-undiscovered genetic defect may develop preeclampsia, according to Dr. Karumanchi. That's why doctors test pregnant women's urine Ã¢â‚¬” if they find protein, it's a sign that the kidneys are malfunctioning and blood pressure is rising. If that happens to you, your doctor will monitor you carefully and perhaps even deliver the baby early to prevent you from suffering the worst-case scenario: seizures, organ failure, and even death.
But Dr. Karumanchi's research isn't all gloomy. He and his colleagues hope to find a way to block excessive sFlt1. Within 5 years, your child's attempts to raise your blood pressure may be in vain Ã¢â‚¬” at least until his or her teenage years.
[Round 3] Pulling Some Punches
I wouldn't want to leave you thinking there's no love or reciprocity in pregnancy. You just have to look hard. In the mid-1990s, Diana Bianchi, M.D., a professor of pediatrics at Tufts University School of Medicine, was trying to develop a new way to test fetuses for Down syndrome when she made an astonishing discovery: She found male stem cells in the blood of women carrying female fetuses. In each case, the cells were from an earlier pregnancy with a boy. Research has since proven that babies leave a part of themselves behind in their mothers, apparently for life.
Unlike the stem cells harvested from frozen embryos that have gotten so much press of late, these cells aren't politically or ethically iffy. They're already inside any woman who has ever been pregnant (even if the pregnancy ended in abortion or miscarriage). And they could be lifesavers. Fetal stem cells have been found clustered at brain and liver injuries in female mice, where they were apparently attempting to repair the damage. "It's certainly conceivable that eventually we will discover how to harness these cells," Dr. Bianchi says, turning them into molecular MASH units. Your son or daughter may someday give you renewed life, as you once gave life to him or her.
Unfortunately, fetal stem cells occasionally turn bad. If their genetic markers are very similar to those of the mother's cells, her immune system can go haywire, leading to autoimmune diseases like scleroderma, which causes hardening of the skin, cartilage, and other connective tissue. As scientists learn more about managing autoimmune diseases, however, they might start checking for the compatibility of cells between mother and child early in a pregnancy to identify which women need early intervention, says J. Lee Nelson, M.D., a professor of rheumatology atthe University of Washington.
For now we can't make decisions about what genes we'll pass to our kids or tell a selfish placenta to keep its proteins to itself. But we can use the emerging science to arm ourselves. Since your baby is going to take as much as he or she can, make sure you get the nutrients you need (see "Eating for Two"). And score some back rubs from Dad, since he's more implicated in your physical hardships than he may realize.
Then take a deep breath and accept that pregnancy is a skirmish that doesn't come close to ending at birth. My son, Max, who is now 9, still commands a breathtakingly disproportionate share of familial resources. Have you priced an Xbox lately? Or orthodontia? Still, as I fold his socks, make him breakfast, and play chauffeur, it's nice to know that someday his stem cells may save my life. I'm going to hold him to that. If you're ever pregnant, I advise you to place your hands on your belly and remind your growing baby that you expect the same. It's never too early to start instilling that sense of powerful obligation that every child should feel toward its mother. That's how, in the end, we wily moms always win.