Week 5-8: The Embryonic Stage
During the embryonic stage, which lasts from week 5 to week 8, the developing embryo goes through significant changes. The embryo’s major organ systems start to develop, and the formation of limbs and digits occurs. At this stage, the embryo is about the size of a grape, and its heart begins to beat, circulating blood throughout the body.
One of the significant milestones during this stage is the development of the neural tube, which eventually becomes the brain and spinal cord. The neural tube’s proper development is crucial, and any abnormalities can lead to severe birth defects such as spina bifida.
At this stage, the embryo’s facial features start to form, including the eyes, ears, and nose. The embryo’s limb buds start to sprout, which will eventually form the arms and legs. Additionally, the embryo’s digestive system and lungs begin to develop, which will become functional later in the pregnancy.
It’s essential to note that during this stage, the developing embryo is vulnerable to external factors such as alcohol, drugs, and certain medications that can cause birth defects. Therefore, it’s crucial for pregnant women to avoid these substances and maintain a healthy lifestyle.
Week 9-12: The Fetal Stage
The fetal stage begins at week 9 and lasts until the end of the pregnancy. During this stage, the developing embryo is now called a fetus, and it undergoes rapid growth and development. At this stage, the fetus is about the size of a lime, and its major organs and systems are now fully formed.
One of the significant milestones during this stage is the formation of facial features, including the nose, lips, and ears. The fetus’s eyes are still widely spaced, but they will eventually move closer together as the pregnancy progresses.
Another significant development during this stage is the fetus’s movement and reflexes. The fetus can now move its arms and legs, and it can even suck its thumb. The fetus’s nervous system is also developing rapidly, allowing it to respond to external stimuli such as sound.
It’s also during this stage that the fetus’s gender can be determined through ultrasound. Additionally, the fetus’s skin is transparent, and the veins are visible, giving the fetus a reddish appearance.
As the pregnancy progresses, the fetus will continue to grow and develop, and it’s essential for pregnant women to continue receiving prenatal care to ensure the fetus’s healthy development. Regular check-ups with a doctor or midwife can help detect any potential issues early on and ensure the best possible outcome for both the mother and the baby.
Week 13-16: Second Trimester
During the second trimester, which spans from weeks 13 to 16, the fetus continues to grow and develop at a rapid pace. It is during this period that the nervous system begins to develop, and the fetus starts to exhibit more complex reflexes. The fetus’s gender is also determined during this time.
Continued Growth and Development
During the second trimester, the fetus develops rapidly, and its body systems continue to mature. The fetus measures around 3.5 inches and weighs about 1.7 ounces by the end of the 16th week. Its bones begin to harden, and its body starts to become more proportionate.
Development of the Nervous System
The nervous system begins to develop during the second trimester. The brain continues to grow, and the nervous system starts to function. The fetus starts to make complex movements and even exhibits reflexes such as sucking its thumb, yawning, and moving its eyes.
The fetus’s sex is determined during the second trimester. Most parents eagerly await this milestone and may even choose to have an ultrasound scan to confirm the baby’s gender. The fetus’s genitals are visible by the end of the 16th week, and the doctor can determine the sex of the baby.
Week 17-40: Third Trimester
The third trimester is the final stage of fetal development, spanning from week 17 to birth. During this time, the fetus undergoes significant changes to prepare for birth. The lungs and other vital organs continue to develop, and the fetus gains significant weight.
Final Stages of Fetal Development
During the third trimester, the fetus undergoes significant changes to prepare for birth. Its bones continue to harden, and its body grows plumper as it gains weight. The fetus also practices breathing movements in preparation for life outside the womb.
Preparation for Birth
As the due date approaches, the fetus moves lower into the mother’s pelvis, preparing for birth. The baby’s head may engage, which means it moves into a position that will allow for a smooth delivery. The mother may also experience Braxton Hicks contractions, which are practice contractions preparing the uterus for labor.
Development of the Lungs and Other Vital Organs
The final weeks of pregnancy are crucial for the development of the lungs and other vital organs. The lungs start to produce surfactant, which is a substance that enables the lungs to expand and contract easily. The liver, kidneys, and digestive system also continue to mature, preparing the fetus for life outside the womb.
Understanding fetal development week by week is essential for expectant mothers. It provides valuable insight into the changes that occur during pregnancy and helps mothers prepare for childbirth and motherhood. At Mama Knows Best, we provide comprehensive information on various aspects of motherhood, including pregnancy, childbirth, breastfeeding, and raising children. Knowing what to expect during each stage of pregnancy can help mothers make informed decisions about their health and the health of their babies.