You. Your Pregnancy. Your Baby.

Pregnancy Calendar: Week Twelve

This week marks the end of the first trimester. And a milestone in your baby's development. Growing inside you is a living being which shares the genetic information of you and your partner.

The last few months have seen the fertilization of the ovum to create a cell which has split, grown and developed into a recognizable human form. You have achieved a lot over the last ten weeks. But the most exciting part is yet to come!

External details

Your baby's face is completely formed with its eyes in front of its head, still quite large, widely spaced and shut. Your baby's ears are now higher on the side of the head.

Thirty two permanent tooth buds have been formed in the baby's jaws and your baby will now begin to suck. Your baby's body is now also complete with small arms and legs which are beginning to move.

Fingers and toes are appearing and nails are starting to grow. There is the suggestion of a neck separating the body from the head.

Internal details

Your baby's bone tissue has begun to form complete with joints. Ossification, the process which hardens cartilage into bone will continue and will not be complete until your child reaches adolescence. The skin is still translucent and permeable to amniotic fluidThe liquid, which is produced by both the fetal membranes and the fetus that surrounds the baby during pregnancy. The liter of fluid at term serves to protect the fetus during pregnancy and also provide active chemical exchange.
The amniotic fluid consists of maternal and fetal plasma in varying concentrations. The pH of the fluid is almost neutral and clear, although lipids and desquamated fetal cells can make it cloudy.
Visit our comprehensive glossary for more pregnancy terms and definitions.
.

Inside your baby's body all organs are completely formed. The heart is operational and pumping blood throughout the body and the stomach is linked to the mouth and intestines.

Ovaries or testes are formed inside the body, but no external signs are visible to determine the baby's sex.

Your changing body

Pregnancy Tip!
  • Buy some good quality fragrance free moisturizing cream. The skin on your abdomen and breasts may become dry or tight.

Until now, your ovaries have provided the hormones progesteroneOne of the two naturally occuring female hormones (the other is estrogen) used to regulate and maintain the pregnancy. Produced first by the corpus luteum in the ovary, production is subsequently taken over by the placenta as it develops. During pregnancy a mother's production of progesterone ten times the level it was prior to conception. Progesterone and estrogen are responsible for giving many mothers a sense of tranquility, shiny hair and glowing skin.
Visit our comprehensive glossary for more pregnancy terms and definitions.
and estriolA natural human estrogen that is found in the urine and blood. Measurement may be taken during the last trimester to determine the effectiveness of the placenta.
Visit our comprehensive glossary for more pregnancy terms and definitions.
. This function is now replaced by the placentaThe placenta is a large disk shaped membrane responsible for providing nourishment to the fetus during pregnancy. It consists of three parts, the fetal part made up from the chorion membrane surrounding the fetus, the maternal part, formed from the decidua basalis layer of the uterine lining, and the intervillous space between the two plates. It is connected to the fetus by the umbilical cord and consists of tissue from both the mother and the embryo.
Its function is complex. It has been described as a simple organ that combines the functions of a kidney-dialysis machine, heart and lung machine and intravenous drip. It consists of enormous numbers of blood vessel branches that permit the exchange of nutrition and oxygen, from the mother's bloodstream to the fetus and the removal of wastes to the mother to be excreted. The placenta's remarkable quality is that it does so without the blood of the mother mixing with that of the baby.
It also is responsible for the production of vital hormones including, estrogen, progesterone, and human chorionic gonadotropin. After birth, the placenta is delivered, and is sometimes referred to as the afterbirth.
Visit our comprehensive glossary for more pregnancy terms and definitions.
, which helps to induce the changes necessary to your body throughout your pregnancy.

Your body will adjust to this flow of hormonesA complex chemical substance created in a part or organ of the body. When released it initiates or regulates activity in an organ or group of cells in another part of the body.
Hormones secreted by endocrine glands are transported through the bloodstream to their target organ. The amount of hormone secreted is regulated either by other hormones, by neurotransmitters, or simply when an excess of the organ's activity indicates a need to reduce the amount of the hormone produced.
Other hormones are produced locally by the organs themselves and are common in the digestive tract.
Visit our comprehensive glossary for more pregnancy terms and definitions.
in your bloodstream, and this week your
morning sickness should be nearly over. The placentaThe placenta is a large disk shaped membrane responsible for providing nourishment to the fetus during pregnancy. It consists of three parts, the fetal part made up from the chorion membrane surrounding the fetus, the maternal part, formed from the decidua basalis layer of the uterine lining, and the intervillous space between the two plates. It is connected to the fetus by the umbilical cord and consists of tissue from both the mother and the embryo.
Its function is complex. It has been described as a simple organ that combines the functions of a kidney-dialysis machine, heart and lung machine and intravenous drip. It consists of enormous numbers of blood vessel branches that permit the exchange of nutrition and oxygen, from the mother's bloodstream to the fetus and the removal of wastes to the mother to be excreted. The placenta's remarkable quality is that it does so without the blood of the mother mixing with that of the baby.
It also is responsible for the production of vital hormones including, estrogen, progesterone, and human chorionic gonadotropin. After birth, the placenta is delivered, and is sometimes referred to as the afterbirth.
Visit our comprehensive glossary for more pregnancy terms and definitions.
is also providing your baby with most of the nutrients it needs as well as oxygen and removal of bodily waste.

Your uterus is growing at a steady rate and should be quite noticeable. The amnionA membrane that surrounds the amniotic cavity, covering the fetal side of the placenta and the outer surface of the umbilical cord. It also becomes the outermost layer of skin on the developing fetus.
Visit our comprehensive glossary for more pregnancy terms and definitions.
is filled with amniotic fluidThe liquid, which is produced by both the fetal membranes and the fetus that surrounds the baby during pregnancy. The liter of fluid at term serves to protect the fetus during pregnancy and also provide active chemical exchange.
The amniotic fluid consists of maternal and fetal plasma in varying concentrations. The pH of the fluid is almost neutral and clear, although lipids and desquamated fetal cells can make it cloudy.
Visit our comprehensive glossary for more pregnancy terms and definitions.
, which protects your baby from bumps. It also keeps your baby warm while allowing it to move.

This week marks the end of your first trimester, and your risk of miscarriage greatly reduces. Rest assured that any feelings of anxiety you have had should be diminished.


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