Like your own ear, your baby's ear is made of soft and flexible cartilage. Although the outer ear is well developed at this stage, inner ear structures will not be mature enough to enable your baby to hear for about another five weeks.
The sex of your baby should now be apparent on an ultrasound scan, but you may not have this for a couple of weeks yet (see Finding out the sex of your baby).
Whether your baby develops into a boy or a girl depends on the presence or absence of a Y chromosome. Males are XY and the Y chromosome instructs the reproductive glands (gonads) to become testes. These then produce testosterone and other hormones that inhibit the development of the female organs and in turn stimulate the normal development of the external male genitalia.
If there is no Y chromosome, the gonad becomes an ovary and the internal genitals are female by default; it's not the ovary that dictates that the female reproductive organs will develop but the lack of testosterone. In the female the uterus is formed first and the vagina lengthens upward to meet it.
Many women have a strong opinion about whether or not they want to find out the sex of their baby at the 20-week ultrasound, but others are ambivalent. If your partner has strong feelings one way or the other, you can choose to follow his lead. Otherwise, try to figure out your feelings by deciding if you want to choose two names (boy and girl) and get mostly yellow and green baby clothing at your shower, or if identifying with the baby's gender will make these upcoming baby tasks more enjoyable for you.
When one person in a relationship wants something that is at odds with what his or her partner wants, tensions can arise.
Like you, I wanted to find out the sex of my baby but my partner didn't. We both explained our reasons: I felt that knowing the sex would better help me prepare for the birth, both emotionally and practically; my partner said he wanted the surprise element of discovering the sex of the baby at the actual birth.
Talk to each other openly and hopefully you'll be able to reach an agreement. Try not to let the issue get out of hand and consider backing down if necessary. It's important that you feel united at this special time.
You may find either one of you doesn't feel as strongly once you start talking. You could agree to find out but not tell anyone else. If you do find out, don't forget the result is not 100 percent accurate.
Excerpted from Pregnancy Day by Day.
Copyright ©2009 Dorling Kindersley Limited.
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