Dr. Oz and Dr. Roizen on Pregnancy and Your Genes

Nov. 30, 2009— -- Dr. Mehmet Oz and Dr. Michael Roizen have a new book out tackling pregnancy, called "YOU: Having a Baby: The Owner's Manual to a Happy and Healthy Pregnancy."

Read the excerpt below, and then head to the "GMA" Library to find more good reads.

Back in tenth-grade biology class, you were probably taught -- as were we -- that the unique combination of genes you received from your mom and dad (your genotype) was responsible for everything that followed: the color of your eyes, the size of your feet, your love of lasagna, your hatred for all eight-legged and no-legged creatures. To a certain extent, that's true, but over the past few years, studies have suggested that classical genetics may be only part of the picture.

It's not just your genes that determine who you are, but which of those genes are turned on, or expressed, and to what degree they are expressed -- a cutting-edge field called epigenetics.While you can't control which genes you pass on to your child, you do have some influence over which genes are expressed, affecting what features are seen in your baby (his phenotype).

In this chapter, after giving you a brief refresher on the basic biology of what happens after your life-changing evening of romantic rasslin', we're going to introduce you to a new subject: YOU-ology -- how what you eat, breathe, and even feel can affect the long-term health of your child.

Two to One: The Biology of Conception

We trust that you know the ins and outs of the process that involves his part A and her part B, so we'll skip what happens deep under the satin sheets and focus on the miracle deep below the flesh and deep inside the body -- that is, how the egg and sperm come together.*

The Eggs

On the female side of the conception equation lie her eggs, which are fully formed and stowed away in her ovaries from before birth. Each mature egg contains one copy of each gene in the human genome -- half the amount necessary for life. The maximum number of eggs that a woman will ever have is the number she has when she is a twenty-week-old fetus. She'll have about 7 million of them then, 600,000 when she's born and about 400,000 at puberty. Once a woman hits puberty and menstruation begins, her ovaries release one of those eggs every twenty-eight or so days. During each cycle, even though multiple eggs start to develop, hormonal signals ensure that only a single egg will be released and the other eggs will regress.

(It's not wise evolutionarily to blow them all at once, so the body gives females an approximately thirty-year window in which to conceive.) Hormones also work to mature that ready-to-drop egg and to pop a hole in its sac. That hole works as an escape hatch, so the egg can slip out of the ovary and travel down the Fallopian tube, where it may be fertilized by sperm.**

Tissue left behind in the ovary after the egg is released, called the corpus luteum, will produce hormones essential to successful pregnancy if the egg is fertilized.

* Please cue "Let's Get It On" by Marvin Gaye.**Interestingly, too little of these hormones may lead to infertility or miscarriage, while an abundance may lead to twins and other multiple sets.

CLICK HERE to read more from "YOU: Having a Baby" and to view all of the charts, diagrams and images from the chapter.