How your baby will grow
Although you’re not pregnant yet, you may be about to release an egg that could grow into a baby if it’s fertilized by a sperm.
Last week an increase in the amount of estrogen and progesterone coursing through your bloodstream prompted your uterus to produce a lush, blood-rich lining of tissue to support a potential fertilized egg. At the same time, in your ovaries, eggs were ripening in fluid-filled sacs called follicles.
At the beginning of this week (around day 15 of a 28-day cycle), you may ovulate. When this happens an egg erupts from its follicle and is swept from your ovary into a fallopian tube. (Note that the day of ovulation can vary quite a bit. For example, it could happen between day nine to day 21 for women with a 28-day cycle.)
During the next 24 hours, that egg will be fertilized if one of the nearly 250 million sperm in each ejaculation manages to swim all the way from your vagina through your cervix, up through your uterus to the fallopian tube, where it can penetrate the egg. Only about 400 sperm survive the arduous 10-hour journey to the egg, and only one can succeed in burrowing through its outer membrane.
Over the next 10 to 30 hours, the sperm’s nucleus merges with the egg’s and they combine their genetic material. If the sperm carries a Y chromosome, your baby will be a boy. If it’s an X chromosome, you’ll be carrying a girl.
During the three- to four-day trip from your fallopian tube to your uterus, the fertilized egg (now called a zygote) will divide into 16 identical cells. Once it enters the uterus, the zygote is called a morula. A day or two later, it will begin burrowing into the lush lining of your uterus, continuing its amazing growth and transformation.
By this time, your developing baby is a little ball of cells that’s officially referred to by scientists as a blastocyst: It has an inner cell mass that will become the embryo itself and a fluid-filled cavity that will become the amniotic sac. An outer cell mass will become the placenta, the pancake-shaped organ that delivers life-sustaining oxygen and nutrients to your baby and carries away waste products.
Note: Every baby develops a little differently – even in the womb. Our information is designed to give you a general idea of your baby’s development.
How your life is changing
A lot of things have to fall into place for conception to happen – in this case, timing really is everything. To boost your odds, aim to have sex during the two days before you ovulate and again on the day you think you’re ovulating. Make sure you and your partner have plenty of time together to make love.
You also might want to do some homework beforehand: Read up on detecting ovulation to help you pinpoint your window of opportunity. And find out how long it usually takes to get pregnant – most couples need more than a few tries before they can announce that a baby’s on the way.
And if you haven’t already, see your healthcare provider for a preconception checkup to make sure your body is in the best possible shape for baby-making. For example, she’ll offer you genetic carrier screening to see whether you or your partner is a carrier for serious inherited illnesses. And if you’re taking any prescription or over-the-counter drugs, ask her whether you should continue taking them.
If you succeed in conceiving, it could be two weeks or more before you get a positive result on a pregnancy test.
Most babies are born about 38 weeks after the egg is fertilized, but because it’s often difficult to pinpoint exactly when that happened, your healthcare provider calculates your due date by counting 40 weeks from the first day of your last period, assuming your cycle is about 28 days. (If you have shorter or longer cycles, you may have your due date adjusted after an ultrasound.)
Learn about: Baby-making sex myths
Are some sexual positions better than others for conceiving?
There’s no evidence that any particular sexual position is more likely to lead to conception. You may have heard that certain positions, such as the missionary position (man on top), are more promising than others because sperm is deposited closest to the cervix, but there are no studies to back this up.
Does having an orgasm boost my chances of conceiving?
Some people believe that a woman who climaxes after her partner ejaculates is more likely to get pregnant, but there isn’t any evidence to support this either.
The female orgasm isn’t necessary for conception, but it is possible that uterine contractions from an orgasm may propel sperm toward the fallopian tubes. (The uterus also contracts involuntarily when you’re not having sex, especially around the time of ovulation.)
Should I stay lying down afterward?
You may have heard that remaining horizontal for 15 minutes or so after intercourse allows semen to remain in your vagina longer, but there’s no evidence that this makes a difference. There are millions of sperm in each ejaculation, so there should be plenty in your vagina even if you get up right away.
Activity: Stock up on prenatal vitamins
If you haven’t already, now’s the time to start taking a daily prenatal vitamin. Make sure yours contains at least 400 micrograms of folic acid to reduce your baby’s risk of certain birth defects. To help you remember to take one every day, put your bottle of vitamins next to your toothbrush or something else you’re sure to see before bed or in the morning.