From the moment of conception to the time of delivery, your growing baby goes through several stages of development. The first third of your pregnancy is called the first trimester. It’s made up of weeks 1 through 12 or 13 of pregnancy. Here is a summary of how your baby develops during the first trimester. Show
Path to improved healthPregnancy begins when a man’s sperm fertilizes a woman’s egg. Since you don’t always know when fertilization occurred, doctors calculate pregnancy based on the first day of your last menstrual period (LMP). Your doctor will count forward 40 weeks from your LMP to estimate the due date. Most births occur between weeks 38 and 42. If you have an ultrasound early in your pregnancy, your doctor may measure the baby to determine your due date instead. After conception, your baby begins a period of dramatic change known as the embryonic stage. This stage runs from the 5th through the 10th week of pregnancy. During this stage, the baby is called an embryo. There are numerous changes that occur during the embryonic stage. First, the cells of the embryo (called embryonic stem cells) multiply and develop. They become the hundreds of different types of cells needed to make a whole human body. Your baby’s major organs and body parts begin to take shape. The placenta forms during the embryonic stage. The placenta takes nutrients, oxygen, and water from your blood and passes these along to your baby through the umbilical cord. It also removes the baby’s wastes. The placenta will filter out most of the harmful substances that may be present in your body. The amniotic sac forms during this stage as well. It is filled with amniotic fluid, which surrounds and protects your baby in the uterus. Below are some of the highlights that occur during the embryonic stage.
By the end of the embryonic stage at week 10 of your pregnancy, your baby will be about 1 inch long. That’s still too small for you to feel your baby’s movements. You’ll probably feel them starting in the middle of the second trimester. After the embryonic stage, the fetal stage begins and your baby is called a fetus. This stage runs from the 11th week until birth. Your baby will grow longer and gain weight quicker. His or her organs and body parts will continue to develop. Fingernails and toenails begin to form and the kidneys start working. By the end of the first trimester, your baby has tripled in length to about 3 inches long. Things to considerAs your baby develops in the womb, your body goes through a lot of changes as well. Make an appointment with your doctor if you think or know you’re pregnant. He or she will be able to confirm your pregnancy. Your doctor will also talk with you about your baby’s development and prenatal care. So much important development happens during the first trimester. It is important to not take any medicines without first asking the advice of your doctor. Questions for your doctor
ResourcesAmerican Academy of Family Physicians: Changes in Your Body During Pregnancy: First Trimester March of Dimes: Pregnancy Week by Week National Institutes of Health, MedlinePlus: Fetal Development Copyright © American Academy of Family Physicians This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject. Why are the first 3 months first trimester of a pregnancy the most important developmentally quizlet?- The mother has the most energy during the first 3 months that allow the embryo the energy needed to develop. - The uterus protects and nourishes the embryo during the first 3 months until the placenta begins to develop during the second trimester.
What is the most important trimester for development of a fetus?In general, major defects of the body and internal organs are more likely to occur between 3 to 12 embryo / fetal weeks. This is the same as 5 to 14 gestational weeks (weeks since the first day of your last period). This is also referred to as the first trimester.
Why is the first trimester of pregnancy so critical for ensuring a healthy newborn?The first trimester is so important because most of your baby's major organs and body systems are developing. Toxins, harmful substances and infection can severely damage a fetus's growth and development during this time. It could increase your baby's risk of being born with a congenital disorder.
What is happening developmentally during each trimester of pregnancy?In the first trimester, your baby will grow from a fertilized egg into a moving fetus with eyes, ears, and working organs. In the second trimester, your baby's features develop and you may be able to feel your baby move. In the third trimester, your baby will grow rapidly to get ready for birth.
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