Dad's Guide to Pregnancy For Dummies. Sharon PerkinsЧитать онлайн книгу.
the original eggs just mature, usually one at a time. Mature eggs are produced from immature ones (called oocytes), located in the ovaries, through a complex interaction of three hormones during the menstrual cycle. Those hormones — estradiol (a form of estrogen), follicle stimulating hormone (FSH), and luteinizing hormone (LH) — work like this:
1 Day 1 of the menstrual cycle begins when your partner’s period starts. FSH stimulates the ovaries, which produce estrogen.
2 Estradiol production starts to mature a number of egg-containing follicles, small, cyst like structures that contain the immature eggs.
3 One follicle, called a lead follicle, continues to develop while the rest atrophy.
4 Around day 14 of the menstrual cycle, LH kicks in to mature the egg and move it to the center of the follicle so it can release. Ovulation occurs 14 days before the last day of your partner’s cycle, so day 14 is based on an average 28-day cycle. If her cycles are longer or shorter than 14 days, she’ll ovulate earlier or later.
5 The egg releases from the follicle and begins to float down the fallopian tube. This is where you and your sperm come in.
Figure 2-1 shows the events of a menstrual cycle when pregnancy does not occur.
Illustration by Kathryn Born, MA
FIGURE 2-1: Every event in the menstrual cycle has a purpose.
Sending in some good sperm
Sperm can only fertilize an egg that’s mature, so you need to either have sperm waiting in the tube when the egg is released or get some there within 12 to 24 hours after ovulation, because that’s how long the egg can live.
Illustration by Kathryn Born, MA
FIGURE 2-2: Sperm are compact swimming machines.
Making the journey and attaching to the uterus
After fertilization, the new potential life must make it down the tube to the uterus, where it implants. The journey from fallopian tube to uterus takes five to seven days, on average, and implantation normally occurs seven to ten days after conception. The fallopian tube is normally a fairly straight tube, but if it’s twisted or dilated because of previous infection or pelvic inflammatory disease, the embryo may wander around in the crevasses and never get to the uterus.
WHY SO MANY SPERM?
Women produce one egg a month, most of the time, and men produce millions of sperm. Why the huge disparity? Because one sperm isn’t enough to get the job done — it needs lots of friends to help. Although only one victorious sperm makes it into the egg, breaking down the coating that surrounds the egg takes many sperm. And although eggs get to drift downward from the ovary to the fallopian tube, sperm have to swim upstream. Needless to say, some fall by the wayside, either because they tire or because they take a wrong turn somewhere.
Sperm are also produced in large quantities because many are abnormal, having two tails, no tails, round tails, small heads, large heads, or abnormally shaped heads. Abnormal tails make navigation difficult, and abnormal heads often indicate chromosomal abnormalities.
Only 50 to 60 percent of sperm need good motility, or movement, for a sperm sample to be considered normal, so lots of sperm don’t make the grade, creating a need for higher numbers.
Even worse, the embryo may implant in the fallopian tube, a situation known as an ectopic pregnancy. The tube has no room for a developing fetus, so an ectopic pregnancy is doomed from the start and can cause serious, life-threatening bleeding if the tube ruptures. Ectopic pregnancies occur in around 2 percent of all pregnancies.
Even after the embryo reaches the uterus, it’s not always clear sailing. The uterine lining has to be just right for implantation. Estrogen thickens the lining before ovulation, and progesterone released from the corpus luteum (the leftover shell of the follicle that contained the egg) prepares the lining after ovulation. If either of these hormone levels is low, the lining may not be able to support a pregnancy. Note: Your partner’s medical practitioner can assess the uterine lining by ultrasound and prescribe extra progesterone if needed to achieve and maintain pregnancy.
After the embryo reaches the uterus and implants, the implanted embryo begins to produce human chorionic gonadotropin, or hCG, the hormone that pregnancy tests measure. hCG levels aren’t detectable until the embryo implants, or around the time of the first missed period.
CONCEPTION STATISTICS
If you don’t get pregnant the first month you try, the wheels in your head may start turning as you obsess over why this is taking so long. But pregnancy is by no means a sure thing, even when you do everything right and have no major fertility issues. Statistics say that
Out of 100 couples under age 35 trying to get pregnant over a three month period, 50 achieve their goal, but 20 percent miscarry.
If your partner is in her late 30s, you have a 10 percent chance of pregnancy each month but a 34 percent chance of miscarriage.
If she’s older than 40, you have only a 5 percent chance of pregnancy each month and more than a 50 percent chance of miscarriage.
The good news is that 90 percent of 30-year-olds trying to get pregnant become pregnant within a year, and 66 percent of 35-year-olds get pregnant in a year. Around 44 percent of 40-year-olds become pregnant within a year. Over age 40, variables such as hormone levels affect pregnancy rates, and generalizations are hard to make. Timing intercourse to ovulation can increase the chance of getting pregnant to 76 percent in the first try, for those under 30.
Answering FAQs about getting pregnant
Getting pregnant may seem straightforward, but what exactly does it take? Here are some answers to the most common concerns:
How long does it take to get pregnant?On average, more than half of couples under age 35 get pregnant within the first six months of trying, and four out of five are pregnant within one year.
Does having more sex increase the chances of pregnancy?
No. In fact, due to the amount of time it takes for semen volume to build back up to normal levels following ejaculation, overdoing it around ovulation time by having sex several times a day can deplete your sperm count, which probably won’t be a problem if you have a normal sperm count but can be if your count is low.
Should we only have sex with my partner on her back and me on top?It’s a myth that this standard position is the best way to get pregnant. Although