Monthly Archives: August 2011

Locked Away

August 7, 2011 By in Books, Genes, Pregnancy Tags: , , , , , 3 Comments

The results are in. The ultrasound was conclusive. And despite my previously described hunch that our growing baby is a boy, she turned out to be a girl. We are, of course, ecstatic. A healthy baby and a girl to boot! As everyone tells us, girls are simply more fun.

As I was reading in my pregnancy book the other day, I came across an interesting bit of trivia about baby girls. At this point in my pregnancy (nearly 6 months in), our baby’s ovaries contain all the eggs she’ll have for her entire life. As I mentioned in a prior post, the fact that a female fetus develops her lifetime supply of eggs in utero represents a remarkable transgenerational link. In essence, half of the genetic material that makes up my growing baby already existed inside my mother when she was pregnant. And now, inside me, exists half of the genetic material that will become all of the grandchildren I will ever have. This is the kind of link that seems to mix science and spirituality, that reminds us that, though we are a mere cluster of cells, there’s a poetry to the language of biology and Life.

But after stumbling upon this factoid about our baby’s eggs, I was also struck by a sense that somewhere someone seemed to have his or her priorities mixed up. If our baby were born today, she would have a slim chance of surviving. Her intestines, cerebral blood vessels, and retinas are immature and not ready for life outside the womb. Worse still, the only shot her lungs would have at functioning is with the aid of extreme medical intervention. The order of it all seems crazy. My baby is equipped with everything she’ll need to reproduce decades in the future, yet she lacks the lung development to make it five minutes in the outside world. What was biology thinking?

Then I remembered two delightful popular science books I’d read recently, The Red Queen by Matt Ridley and Life Ascending by Nick Lane. Both described the Red Queen Hypothesis of the evolution of sex, which states that the reason so much of the animal kingdom reproduces sexually (rather than just making clones of itself) is to ‘outwit’ parasites. In short, if each generation of humans were the same as the next, parasites large and microbial could evolve to overtake us. By mixing up our genetic makeup through sexual reproduction, we make it harder for illnesses to wipe us out. Like the Red Queen from Lewis Carroll’s classic, we keep running in order to stay in the same place (which is one step ahead of parasites and disease).

Just as there are parasitic organisms and bacteria, one might say that there are parasitic genes. For example, mutations in the DNA of our own replicating cells can cause cancer, which is essentially a self-made, genetic parasite. Moreover, retroviruses like HIV are essentially bits of genetic material that invade our bodies and can insert themselves into the DNA of our cells. And the ultimate road to immortality for a parasitic gene would be to hitch a ride on the back of reproduction. Imagine what an easy life that would be! If a retrovirus could invade the eggs in the ovaries, it would be passed on from one generation to the next without doing one iota of work. It’s the holy grail of parasitic invasion – get thee to the ovaries! According to Matt Ridley in another of his books, The Origins of Virtue, the human germ line is segregated from the rest of the growing embryo by 56 days after fertilization. Within two months of conception, the cells that will give rise to all of the embryo’s eggs (or sperm, in males) are already cordoned off. They are kept safe until they are needed many years in the future.

So perhaps my little baby’s development isn’t as backwards as it seemed at first. Yes, lungs are important. But when you’ve got something of value to others, it makes practical sense to hurry up and lock it away.

The Trouble with (and without) Fish

August 2, 2011 By in Pregnancy, Science Tags: , , , 1 Comment

Once upon a time in a vast ocean, life evolved. And then, over many millions of years, neurons and spinal cords and eyes developed, nourished all the while in a gentle bath of nutrients and algae.

Our brains and eyes are distant descendants of those early nervous systems formed in the sea. And even though our ancestors eventually sprouted legs and waddled out of the ocean, the neural circuitry of modern humans is still dependent on certain nutrients that their water-logged predecessors had in abundance.

This obscure fact about a distant evolution has recently turned into a major annoyance for me now that I’m pregnant. In fact, whether they know it or not, all pregnant women are trapped in a no-win dilemma over what they put into their stomachs. Take, for instance, a popular guidebook for pregnant women. On one page, it advocates eating lots of seafood while pregnant, explaining that fish contain key nutrients that the developing eyes and brains of the fetus will need. A few pages later, however, the author warns that seafood contains methylmercury, a neurotoxic pollutant, and that fish intake should be strictly curtailed. What is a well-meaning pregnant lady to do?

On a visceral level, nothing sounds worse than poisoning your child with mercury, and so many women reduce their seafood intake while pregnant. I have spoken with women who cut all seafood out of their diet while pregnant, for fear that a little exposure could prove to be too much. They had good reason to be worried. Extreme methylmercury poisoning episodes in Japan and Iraq in past decades have shown that excessive methylmercury intake during pregnancy can cause developmental delays, deafness, blindness, and seizures in the babies exposed.

But what happens if pregnant women eliminate seafood from their diet altogether? Without careful supplementation of vital nutrients found in marine ecosystems, children face neural setbacks or developmental delays on a massive scale. Consider deficiencies in iodine, a key nutrient readily found in seafood. Its scarcity in the modern land-based diet was causing mental retardation in children – and sparked the creation of iodized salt (salt supplemented with iodine) to ensure that the nutritional need was met.

Perhaps the hardest nutrient to get without seafood is an omega-3 fatty acid known as DHA. In recent years, scientists have learned that this particular fatty acid is essential for proper brain development and functioning, yet it is almost impossible to get from non-aquatic dietary sources. At the grocery store, you’ll find vegetarian products that claim to fill those needs by supplying the biochemical precursor to DHA (found in flaxseed, walnuts, and soybean oils), but we now know that the precursor simply won’t cut it. Our bodies are remarkably slow at synthesizing DHA from its precursor. In fact, we burn the vast majority of the precursor for energy before we have the chance to convert it to DHA.

So pregnant women must eat food from marine sources if they are to meet all the needs of their growing babies. Yet thanks to global practices of burning coal and disposing of industrial and medical waste, any seafood women eat will expose their offspring to some amount of methylmercury. There’s no simple solution to this problem, although recent studies suggest that child outcomes are best when women consume ample seafood while avoiding species with higher levels of methylmercury (such as shark, tilefish, walleye, pike, and some types of tuna). Of course much is still unknown. Exactly how much DHA intake is enough? And since mercury levels vary based on where the fish was caught and what waste was released nearby, you can never be sure it’s safe to eat.

Unless we start cleaning up our oceans, pregnant women will continue to face this awful decision each time they sit down at the dinner table. Far worse, we may face future generations with lower IQs and developmental delays regardless of which choice their mothers make. Thanks to shoddy environmental oversight, we may be saddling our children with brains that don’t work as well as our own. And that is something I truly can’t swallow.