Understanding inherited genes

Genetic disease inheritance is complicated and falls into several different patterns; the four most common are:

• Autosomal recessive: A child must inherit the mutation from both parents to have the disease. A child whose parents both carry the gene has a 25 percent chance of having the disease, a 50 percent chance of being a carrier of the disease but not having it, and a 25 percent chance of not inheriting the gene at all. Cystic fibrosis and sickle cell anemia are examples of autosomal recessive diseases. Approximately 80 percent of children born with an autosomal recessive disorder have no evidence of the disease itself in their families. That’s because family members can carry a gene for autosomal recessive disease for generations . . . or forever, without the disease showing up, if no one marries a partner with the same recessive gene. Without two copies of the mutation, one from each parent, a child will not be born with the actual disease.
  
• Autosomal dominant: The child will have the disease even if only one parent passes on the mutation. Huntington’s chorea is an example of this disease. Huntington’s chorea can be passed on because its carriers usually survive long enough to have children and pass on the gene.
  
• X-linked dominant: An X-linked disease is a mutation of the X chromosome. Females are more often affected because they have two X chromosomes. Men can only pass an X chromosome to a daughter (girls have XX sex chromosomes, boys have XY, and mom always passes on one of the Xs) so men can’t pass X-linked disease to their sons. Fragile X Syndrome is an example of this disease.
• X-linked recessive: Both parents must pass on the gene for the child to be affected; one in four will have the disease, two in four will be carriers, and one in four will be free of the disease. Hemophilia is an example of an X-linked recessive disease. More males than females are affected by X-linked recessive disease, and males can’t pass them on the sons.

Genetic diseases impact on fertility

Certain inherited diseases can interfere with getting pregnant. You may already know you have an infertility-causing disease, , or may you just find out when you start trying to get pregnant.
Genetic diseases such as Turner Syndrome in women, Kleinfelter Syndrome in men and cystic fibrosis can cause infertility. Less easily recognized problems, such as deletion of part of the Y chromosome in males, may not be recognized until a fertility workup is done.
About 1 in 500 people has a chromosomal translocation. Translocation of chromosomes may cause an individual no problem and isn’t usually obvious but may cause recurrent miscarriage if passed on by either parent. This is because the translocation in an individual is usually balanced — one piece of a chromosome has been exchanged for another. When the chromosome is passed on, however, it may be “unbalanced,” causing miscarriage or abnormal pregnancy.

How often you should do "it"?

When you’re trying to get pregnant, you need to strike a balance between too much intercourse and not enough. Too much intercourse decreases sperm counts, but if you have too little intercourse, you may miss the right moment for conception. Not having intercourse for more than five days may raise the number of sperm but decrease their motility (the active movement). Intercourse less than two days apart may decrease the sperm count. So how do you figure out when the right time is? When you’re close to ovulating, have intercourse at least every other day; every day is okay, but more than once per day is probably too much. Most doctors recommend the two days before and the day you ovulate as the best time for conception.

How reproduction works?

The time is right, the moon is bright, and it’s time to get pregnant. Here’s what needs to happen:

1. It’s near ovulation; an egg is about to release from its follicle.
2. You and your partner become aroused. Your vagina produces secretions that make it easier for the now erect penis to enter the vagina.
3. During the man’s orgasm, several million sperm are forcefully ejaculated into the vagina. As they pass through the cervix into the uterus, the cervical mucus “filters” the sperm so that they’re ready to penetrate an egg.
4. Your egg releases from the follicle and enters one of your fallopian tubes.
5. The sperm swim through the uterus up to the fallopian tubes; half choose the wrong tube to enter.
6. The next day your egg meets up with several hundred sperm in the fallopian tube, and the sperm all attach themselves to the egg, trying to beat down the door.
7. One sperm breaks through the outer layer of the egg, and the egg immediately becomes impenetrable to the rest of the sperm.
8. The genetic material of the egg and sperm combine, and the newly created embryo drifts down the fallopian tube to the uterus.
9. The embryo implants in the uterine wall and grows, and you miss your period.
10. You’re pregnant! Congratulations.

After sex, just lie there for a while. Don’t jump up and go to the bathroom right away. Let gravity help those little swimmers get to where they need to be. Some doctors advocate placing a pillow under the hips during sex to give gravity a little edge in directing the sperm where they need to be. Doing so probably isn’t necessary. You can also choose whatever position is best for you and your partner. There is no “best” position for making babies.

Recognizing signs of ovulation

You may be able to tell that you’re ovulating in a few simple ways, just by watching the calendar and being observant about your bodily functions. Usually the mucus from your cervix increases around the time of ovulation. It also becomes very thin, clear, and stretchy; you can easily stretch it out a couple of inches. Rising estrogen levels from a developing follicle create this mucus, which is easier for sperm to swim through than your usual thicker mucus and also has an alkaline pH, which helps the sperm live longer. At other times of the month, cervical mucus is acidic. Be sure that you’re not confusing cervical mucus with semen from previous sex or increased secretions from sexual arousal.
Some doctors believe that taking antihistamines may decrease cervical mucus. To be on the safe side, avoid antihistamines around ovulation time. If you have no objection to feeling around inside your vagina, you’ll also notice that your cervix becomes softer, slightly open, and easier to locate with your fingers when you’re about to ovulate. At other times of the month, the cervix is found farther back in the uterus, feels firmer to the touch, and is tightly closed.
If you know how long your cycles are, count back 14 days from the length of your cycle to figure out when you’re probably ovulating. For example, if your cycles are 29 days, you ovulate on day 15. If your cycles are 26 days apart, you ovulate on day 12.
About 20 percent of women have pain called mittelschmertz (German for “middle pain”) when they ovulate. The pain seems to be caused by blood and fluid irritating the tissues around the ovary after it releases from the follicle. Sometimes a small amount of vaginal bleeding occurs with ovulation too. Some women have headaches around the time of ovulation, and others complain of bloating or breast pain. You’re probably already aware of your personal ovulation indicators, but you may have just never paid much attention to them. Now you should. They’re a big help in choosing when to have baby sex.