Pregnancy is an exciting journey filled with anticipation and numerous changes. Understanding each stage of pregnancy can help expectant parents feel more prepared and connected to the growth of their baby. Our comprehensive week-by-week pregnancy calculator provides detailed insights into what to expect each week, helping you navigate this incredible experience with confidence and ease.
Understanding Pregnancy Weeks
Pregnancy is typically divided into three trimesters, spanning approximately 40 weeks from the first day of your last menstrual period (LMP) to the baby’s due date. Each week brings unique developments for both the baby and the mother. Our week-by-week guide ensures you stay informed about these changes, from conception to birth.
First Trimester (Weeks 1-12)
Week 1-2: Conception and Implantation
During the first two weeks of pregnancy, your body is preparing for ovulation and fertilization. While you are not technically pregnant yet, these weeks are crucial for laying the groundwork for your baby’s development.
Week 3: Fertilization
In week three, fertilization occurs when the sperm meets the egg, forming a zygote. This single cell contains all the genetic information necessary to create a new life. The zygote begins its journey to the uterus, where it will implant and begin to grow.
Week 4: Implantation
By week four, the fertilized egg has implanted itself into the uterine lining. This marks the beginning of embryonic development. You might start experiencing early pregnancy symptoms such as mild cramping and spotting.
Week 5: The Embryo Forms
In week five, the embryo is about the size of a sesame seed. The neural tube, which will become the brain and spinal cord, begins to form. This week is crucial for the baby’s development, and you might notice more pronounced pregnancy symptoms like fatigue and nausea.
Week 6: Heartbeat Begins
By week six, the baby’s heart begins to beat. The embryo is now about the size of a lentil. You may experience heightened symptoms, including morning sickness and breast tenderness, as your body adjusts to the pregnancy.
Week 7-8: Rapid Development
Weeks seven and eight are marked by rapid development. The baby’s facial features, including the eyes, nose, and mouth, start to form. The limb buds, which will become arms and legs, are also developing. You might continue to experience pregnancy symptoms and should start considering your prenatal care options.
Week 9: Fetal Growth
At week nine, the embryo is now referred to as a fetus. It is about the size of a grape. Major organs, including the heart, brain, and kidneys, are developing rapidly. This is a crucial period for avoiding harmful substances and maintaining a healthy lifestyle.
Week 10: Vital Organs Develop
By week ten, the fetus’s vital organs are fully formed and beginning to function. The baby is about the size of a kumquat. You might start noticing changes in your body, such as weight gain and a growing belly.
Week 11-12: Nearing the End of the First Trimester
Weeks eleven and twelve mark the end of the first trimester. The fetus is now about the size of a lime, and its bones are beginning to harden. You might start to feel more energetic as early pregnancy symptoms subside.
Second Trimester (Weeks 13-26)
Week 13-14: Continued Growth
As you enter the second trimester, the baby continues to grow rapidly. By week fourteen, the fetus is about the size of a lemon. You may notice a baby bump starting to show as your uterus expands.
Week 15-16: Developing Senses
During weeks fifteen and sixteen, the baby’s senses start to develop. The eyes can now detect light, and the ears are positioning correctly. You may feel the first flutters of movement, known as quickening.
Week 17-18: Gender Reveal
By weeks seventeen and eighteen, the baby’s genitals are developed enough to determine the gender through an ultrasound. The baby is now about the size of a bell pepper. You might experience round ligament pain as your body adjusts to the growing baby.
Week 19-20: Halfway Mark
At week twenty, you are halfway through your pregnancy. The baby is about the size of a banana. You may start to experience more pronounced fetal movements and should continue regular prenatal check-ups.
Week 21-22: Baby’s Movements
Weeks twenty-one and twenty-two are marked by increased fetal movements. The baby is now about the size of a carrot and developing a sleep-wake cycle. You might start to feel Braxton Hicks contractions as your body prepares for labor.
Week 23-24: Viability
By weeks twenty-three and twenty-four, the baby is considered viable, meaning it has a chance of survival if born prematurely. The baby is about the size of an ear of corn. You should be vigilant about any signs of preterm labor.
Week 25-26: Preparing for Birth
During weeks twenty-five and twenty-six, the baby continues to grow and develop. The baby is now about the size of a head of lettuce. You may start to experience more discomfort as your belly grows and should focus on maintaining a healthy diet and exercise routine.
Third Trimester (Weeks 27-40)
Week 27-28: Entering the Final Stretch
As you enter the third trimester, the baby continues to mature and gain weight. The baby is now about the size of an eggplant. You might experience more frequent Braxton Hicks contractions and should start preparing for the baby’s arrival.
Week 29-30: Rapid Brain Development
During weeks twenty-nine and thirty, the baby’s brain is developing rapidly. The baby is about the size of a butternut squash. You might experience increased fatigue and should focus on getting enough rest.
Week 31-32: Increased Movement
By weeks thirty-one and thirty-two, the baby is about the size of a coconut. You may notice more pronounced and frequent movements as the baby becomes more active. Regular prenatal visits are crucial during this time.
Week 33-34: Lung Development
Weeks thirty-three and thirty-four are critical for lung development. The baby is now about the size of a pineapple. You might start to experience more discomfort and should consider taking childbirth classes.
Week 35-36: Final Preparations
As you approach the end of your pregnancy, the baby is about the size of a honeydew melon. You might experience more frequent Braxton Hicks contractions and should have your hospital bag packed and ready.
Week 37-38: Full-Term
By weeks thirty-seven and thirty-eight, the baby is considered full-term and can be born at any time. The baby is now about the size of a Swiss chard. You should continue regular prenatal check-ups and monitor any signs of labor.
Week 39-40: Awaiting Arrival
During weeks thirty-nine and forty, the baby is preparing for birth. The baby is now about the size of a watermelon. You should be vigilant about any signs of labor and stay in close contact with your healthcare provider.