Understanding
how pregnancy happens is important. If you want to avoid pregnancy, it
helps to know when a woman is most likely to get pregnant, and when she
is not. If you are trying to become pregnant, it is important to know
when getting pregnant is most likely and the different ways it can
happen.
Whether you are trying to avoid pregnancy, trying to get
pregnant, or are just curious, you may have lots of questions. Here are
some answers about how pregnancy happens.
In order for a woman to become pregnant, she must release an egg from her ovary
— ovulation. Next, the egg and sperm must meet and form a single cell —
fertilization. Then pregnancy begins when and if the fertilized egg
attaches to a woman’s uterus and begins to grow — implantation.
MENSTRUATIONDuring the first two weeks of a woman’s menstrual cycle
she has her period. This usually lasts 3–7 days. After that, hormones
make eggs mature in her ovaries, and the lining of her uterus thickens.
OVULATIONOvulation happens about two weeks before a woman’s next period would take place. The egg enters a fallopian tube and starts moving toward the uterus.
FERTILIZATIONAfter vaginal intercourse or alternative insemination,
several hundred sperm travel up through the uterus and into the
fallopian tubes. An egg may be in one of the tubes. One sperm may
fertilize the egg. The millions of other sperm seep out of the vagina or
are absorbed by the woman’s body.
Boy or a Girl? Millions
of sperm are released when a man ejaculates. About half of them have a
gene that could produce a boy. The other half have one that could
produce a girl. |
The joining of egg
and sperm is called fertilization. It is most likely to occur from
sexual intercourse that happens during the five days before the egg is
released or on the day of ovulation.
IMPLANTATIONThe
fertilized egg moves down the fallopian tube and divides into more and
more cells, forming a ball. The ball of cells reaches the uterus about
3–4 days after fertilization.
The ball floats in the uterus for another 2–3 days.
Pregnancy
begins if the ball of cells attaches to the lining of the uterus. This
is called implantation. It usually starts about six days after
fertilization and takes about 3–4 days to be complete. The embryo will develop from cells on the inside of the ball. The placenta will develop from the cells on the outside of the ball.
Twins It
is possible for the developing ball of cells to split up until about
the end of week four. If it splits into two, for example, identical
twins can develop. It is also possible for two eggs to be released at
ovulation. Fraternal — not identical — twins can develop if both eggs
get fertilized by sperm and implant in the uterus. |
Up to half of all fertilized eggs never implant. They pass out of women’s bodies during menstruation.
Gestational Age Pregnancy is measured using “gestational age.” Gestational age starts on the first day of a woman’s last menstrual period (LMP).
Gestational
age can be confusing. Most people think of pregnancy as lasting nine
months. And it’s true that a woman is pregnant for about nine months.
But because pregnancy is measured from a woman’s last menstrual period —
about 3–4 weeks before she is actually pregnant — a full-term pregnancy
usually totals about 40 weeks LMP — roughly 10 months.
Many women
do not remember the exact date of their last menstrual period — that’s
OK. The surest way to tell gestational age early in pregnancy is with
ultrasound. |
How Do Women Get Pregnant?
Women can get pregnant in a variety of ways.
One
common way is through unprotected vaginal intercourse, during which a
man ejaculates sperm into the vagina. The sperm can then travel up
through the cervix, into the uterus, and, if an egg is present, the
sperm may fertilize it.
It is also possible — but less likely —
for women to become pregnant through any kind of sex play in which
semen, or ejaculate, comes in contact with the vulva. The sperm can
travel through the moisture on the vulva into the vagina.
Another
way for a woman to get pregnant is through alternative insemination.
During alternative insemination, sperm are inserted into a woman’s
vagina or uterus using a syringe or other device. The sperm may come
from a woman’s male partner, or from a donor. When a sperm donor is
used, the procedure is sometimes called donor insemination. Alternative
insemination is an option for single women, women who have women
partners, or for couples who are dealing with infertility.
A
woman who is dealing with infertility may also get pregnant through
other fertility treatments like in vitro fertilization. To do this, a
woman’s eggs are taken out of her body and combined with sperm. Then,
one or more of the fertilized eggs are implanted back into the uterus.
When Is Getting Pregnant Most Likely?
A woman's fertile days depend on the life span of the egg and the sperm.
Her egg only lives for about a day after ovulation. Sperm can live
inside her body for about six days. The egg and sperm are most likely to
join when intercourse happens during the five days before the egg is
released or on the day of ovulation. It is also possible for a day or
two after ovulation — even though it's less likely to happen then.
How Can I Avoid Pregnancy?
Using birth control consistently and correctly is the best way a
sexually active woman can avoid pregnancy. There are many safe,
effective birth control options.
How Can I Plan a Pregnancy?
Knowing when your fertile days will happen can help you plan your
pregnancy. The key is to figure out when you will ovulate. This will let
you figure out the other fertile days that come before you ovulate.
Then you can track your fertility pattern — the days of the month when
you are fertile and the days of the month when you are not. You must do
this carefully. Women don't all have the same fertility pattern. And
some women have different patterns from one month to the next.
One
way is to chart your menstrual cycle. The average menstrual cycle is 28
days long, but many women have cycles that are shorter or longer, and
some women have irregular cycles. If you have an irregular cycle, it can
be hard to predict ovulation.
You can also determine your fertile days by tracking your temperature, charting the consistency of your cervical mucus, using beads to keep track of your cycle, or using a combination of these methods to predict ovulation.
Ovulation Predictors Test
kits that attempt to predict ovulation are available for home use. They
may be useful for planning pregnancies. But they are not reliable for
preventing pregnancy. |
Learning about your
fertility pattern is just one step in choosing to become pregnant. There
are many other issues to think about when considering pregnancy — including your emotional and financial readiness, and your health. One way to have the best pregnancy you can have is by planning for it ahead of time.