Wednesday, August 26, 2009

Mmm, sciency!

I just finished the book Making Babies: The Science of Pregnancy by David Bainbridge. The author is a biologist, not an obstetrician, so his point of view was completely different from the other books I've read. He contrasted human pregnancy to that of different kinds of animals, especially mammals. The range among mammals is pretty astounding, regarding all the steps of procreation. How many eggs, when are they released, how many are fertilized/rejected, how the body reacts during pregnancy, etc. Did you know that humans and Old World primates are the only ones with monthly menstruation? Dogs do have some form of estrus involving what looks like menstruation but actually is different. The whole "shed your lining" thing is pretty much just us. I guess dealing with PMS and the mess is preferable to going into heat once or twice a year.

I learned so much about the process going on inside. The transformation is rather amazing. The baby's eyes, for example, grow from the stalks outward, but the lenses actually start as separate pieces that move inward. My mind filled with visuals of lungs sprouting from the early esophagus and the rest of the tube growing in odd spurts to make the bends of the entire gastrointestinal tract.

Just as you begin to succumb to the awe of the perfection of it all you read about the "first kidney". The first kidney the baby develops is actually grown in its throat. No kidding. This kidney serves no purpose at all. Even as it is finishing it's formation, it is taken apart, and eventually completely vanishes. Our closest relative that actually makes use of this phantom organ is the lamprey. The second kidneys that are formed actually function as kidneys for a while, but eventually become the reproductive organs. Can you imagine transforming from filtering waste to producing eggs or sperm? It's only after that that the baby makes the real kidney set. Crazy.

It's a common misconception that babies go through different "evolutionary stages" in the womb. No, they don't start out as amoebas, become fish, lizards, etc. There are differences between our development and animal development from the very beginning to the very end. However, what they do have is similar starting points, rudimentary forms that have been completely repurposed. For instance, no, embryos do not develop gills. They do have primitive structures called "pharyngeal arches" that become gills in fish, but become all different specialized things in humans, from your thyroid to your facial muscles to pieces of your inner ear.

There are more amazing embryo comparisons than I can remember. You know how your basic fish has a horizontal line running down it's side? This line is a sensory organ that detects electromagnetic changes in the water around it, among other things. The basic structures that grow into this sensory organ in fish are present in a human embryo - and they become the taste buds on the surface of your tongue. Awesomeness.

Pretty much everyone has heard of amniotic fluid. It's the stuff the baby is immersed in. When the "water breaks", it's amniotic fluid pouring out. There's a test called "amniocentesis" which involves extracting some of it for testing. But what is the stuff? It's...well, it's fetus urine. The fetus does actually pass liquids, and it then swims, breathes, and lives in it the whole time. Yes, really. Obviously the type of "urine" the fetus makes is totally different than the urine it passes after it's born, but it still makes you think, both about how weird and how amazing this process is. (I know I read this factoid before I read this book, but this book hit it home.)

Other great stuff in there - detailed accounts of the history of prenatal science and the scientists behind them, including those that were debunked and those that were ahead of their time.

All that said, if I were to recommend this book, I'd mention a few caveats. Printed in 2000, it talks about the controversies of fertility science, yet the term "stem cell" is never mentioned, as it was all too new then. Also, I wasn't a huge fan of the author's tone. Everything was conflict - the baby struggling to survive, the mother struggling to bear the child. I know that these struggles are real but he did seem to harp on them.

Still, it was easy to look past the tone and read the hard science. I'll even give him a special boost because he talked a lot about what we don't know. There is still plenty to be learned, and this, too, is somehow comforting...though maybe in the 9 years since it was printed, all that was solved. Right?


  1. Love the cool science! I can imagine seeing a video sped up to show the organs developing like you form the baby. Cool visuals!

  2. I totally want to check out that book. The whole process of gestation is so fascinating and awe-inspiring to me. One of my favorite books growing up was _A Child Is Born_, with photos from pre-conception through birth. I bought an updated copy when I got pregnant and kept looking at the photos to see what my fetus was up to at each stage along the way.

  3. Wow! There are things I didn't know about the human body. Fascinating stuff!

    I found out that some places are now offering to "bank" stem cells from your newborn's cord, in hopes they can be used to help with any future diseases that they might contract. It's interesting:, if you want to check it out.

  4. Very interesting. Since having my girls, and especially one with heart defects, I'm fascinated by how we form and how amazing it really is that so many of us get here intact with nothing whatsoever wrong with us. I once watched a Grand Rounds presentation on heart defects by the surgeon who operated on Zoe, and he said that since the heart starts forming so early, if one thing goes wrong with it, lots of other things will too because the organ naturally wants to try to find a way around the initial problem. This is why you very rarely find a person with heart defects with only 1- many times there are multiple facets going on. I'll definitely have to take a look at that book, it seems really interesting.