**Week 1:** Conception occurs when a sperm fertilizes an egg. The fertilized egg, now called a zygote, begins to divide as it travels down the fallopian tube toward the uterus..
**Week 2:** The zygote continues to divide as it travels through the fallopian tube. By the end of this week, it has reached the uterus and implanted in the uterine lining. The placenta, which will nourish the fetus throughout pregnancy, begins to develop..
**Week 3:** The embryo, which is now about the size of a poppy seed, begins to develop three layers of cells: the ectoderm, mesoderm, and endoderm. These layers will eventually give rise to all of the organs and tissues in the body..
**Week 4:** The embryo’s heart begins to beat. The neural tube, which will eventually become the brain and spinal cord, begins to form..
**Week 5:** The embryo’s arms and legs begin to develop. The face begins to take shape, with the eyes, nose, and mouth forming..
**Week 6:** The embryo is now about the size of a lentil. The eyelids begin to form, and the fingers and toes start to develop..
**Week 7:** The embryo’s external genitalia begin to develop. The fetus is now about the size of a blueberry..
**Week 8:** The fetus’s major organs are now formed. The fetus begins to move and make small gestures..
**Week 9:** The fetus’s heartbeat can now be detected with a Doppler ultrasound. The fetus is now about the size of a grape..
**Week 10:** The fetus’s fingers and toes are now fully formed. The fetus begins to produce urine..
**Week 11:** The fetus’s sex can now be determined by ultrasound. The fetus is now about the size of a strawberry..
**Week 12:** The fetus’s kidneys begin to function. The fetus begins to swallow amniotic fluid..
**Week 13:** The fetus’s hair begins to grow. The fetus is now about the size of a lemon..
**Week 14:** The fetus’s movements become more pronounced. The fetus is now about the size of an avocado..
**Week 15:** The fetus’s skin begins to thicken. The fetus is now about the size of an apple..
**Week 16:** The fetus’s eyes begin to open. The fetus is now about the size of a pear..
**Week 17:** The fetus’s fingernails begin to grow. The fetus is now about the size of a turnip..
**Week 18:** The fetus’s hearing is now fully developed. The fetus is now about the size of a bell pepper..
**Week 19:** The fetus’s movements become even more pronounced. The fetus is now about the size of a mango..
**Week 20:** The fetus’s skin begins to smooth out. The fetus is now about the size of a banana..
**Week 21:** The fetus’s eyebrows and eyelashes begin to grow. The fetus is now about the size of a carrot..
**Week 22:** The fetus’s hair begins to darken. The fetus is now about the size of a zucchini..
**Week 23:** The fetus’s lungs begin to mature. The fetus is now about the size of a grapefruit..
**Week 24:** The fetus’s eyelids begin to open and close. The fetus is now about the size of a cantaloupe..
**Week 25:** The fetus’s sucking reflex is now fully developed. The fetus is now about the size of a cauliflower..
**Week 26:** The fetus’s skin begins to thicken again. The fetus is now about the size of a pineapple..
**Week 27:** The fetus’s fingernails are now fully grown. The fetus is now about the size of a coconut..
**Week 28:** The fetus’s brain begins to grow rapidly. The fetus is now about the size of a head of lettuce..
**Week 29:** The fetus’s eyes begin to focus. The fetus is now about the size of a butternut squash..
**Week 30:** The fetus’s lungs are now fully mature. The fetus is now about the size of a cabbage..
**Week 31:** The fetus’s body begins to fill out. The fetus is now about the size of a watermelon..
**Week 32:** The fetus’s skin becomes even thicker. The fetus is now about the size of a pumpkin..
**Week 33:** The fetus’s head begins to engage in the pelvis. The fetus is now about the size of a turkey..
**Week 34:** The fetus’s lungs are now fully mature. The fetus is now about the size of a small car..
**Week 35:** The fetus’s movements become more restricted as it runs out of room in the uterus. The fetus is now about the size of a honeydew melon..
**Week 36:** The fetus’s skin begins to dry out. The fetus is now about the size of a papaya..
**Week 37:** The fetus’s head is now fully engaged in the pelvis. The fetus is now about the size of a pineapple..
**Week 38:** The fetus is now about the size of a watermelon. The fetus is now ready to be born..
**Week 39:** The fetus is now about the size of a full-term baby. The fetus is now ready to be born..
**Week 40:** The average length of a full-term pregnancy is 40 weeks. The fetus is now ready to be born..
