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blastocyst resting on the lining of the uterus

What's happening inside

The blastocyst prepares to embed itself in the lining of the uterus-the endometrium. Once it is completely implanted-usually around seven days after fertilization-the pregnancy will become established.

Your reproductive organs undergo complex processes that will enable your body to maintain the pregnancy.

If you have conceived, the ball of cells known as the blastocyst that will eventually form the fetus will now be preparing to embed in the lining of your uterus, and the placenta will be starting to form.

Before this happens, however, there is another important change going on. After you ovulate, the empty ovarian follicle develops into a structure called the corpus luteum (which means, literally, "yellow body"). This small, fluid-filled sac becomes increasingly "vascular," developing blood vessels and beginning to produce the hormone progesterone. This is required to create mucus to allow your fertilized egg to survive, and build up the lining of your uterus, in which the blastocyst will soon imbed (see You are 3 Weeks Exactly).

The corpus luteum also produces a little estrogen. By about 8-12 weeks of pregnancy, your placenta will take over the production of progesterone, but the corpus luteum continues to play a small role in hormone production until about six months, when it usually shrinks away.

Ask A... Doctor

Should I stop taking medication in case I've conceived?

Many medicines are safe to take, but some are not, or have not been fully evaluated. This last group includes many antihistamines for allergies, over-the-counter sleeping pills, and many analgesics.

If you've accidentally taken an over-the-counter remedy that's not considered appropriate for use in pregnancy, you're unlikely to have done any harm with just one dose. However, seek medical advice if you're concerned.

If you need to continue using a medicine in pregnancy, ask if it's safe to do so. While pharmacists are well-informed on all medicines, your doctor is the best person to consult on prescription-only drugs.

woman reading medication label

The miracle of conception

When you consider the multitude of events that have to fall neatly into place before a baby is conceived, it's hard to believe that anyone can become pregnant. No wonder they talk about the miracle of life!

To become pregnant the following have to happen:

  • Your hormone balance must be correct for the egg to develop.
  • Ovulation must take place: if you don't release an egg, there is no way for fertilization to occur.
  • You need to have sex at the right time in your menstrual cycle; sperm can last about three days in healthy cervical mucus, but if your timing is off, egg and sperm are unlikely to meet. In some cases there may be only two or three days each month when you can conceive.
  • Your partner needs to produce plenty of good, healthy sperm that can penetrate your cervical mucus to reach the egg.
  • When the egg has been fertilized, the blastocyst has to implant securely in the lining of the uterus.
  • The right levels of the hormone progesterone must be produced by the corpus luteum to maintain the pregnancy.

excerpted from:

Excerpted from Pregnancy Day by Day.
Copyright © 2008 Dorling Kindersley Limited.
Buy this book now!

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