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Ovulation
Ovulation is the release of an egg from your ovary, into your fallopian tube. It typically happens about 13–15 days before the start of each period. -
Conception
Conception occurs when a sperm cell from a fertile man swims up through the vagina and into the uterus of a woman and joins with the woman’s egg cell as it travels down one of the fallopian tubes from the ovary to the uterus. -
1st Trimester / 4 Weeks
Size: 0.04 inches Weight: 0.02
Development: The fetus rapidly divides into layers of cells, some of which become the embryo. The cell layers will start to grow into different parts of your little one's body, such as the nervous system, skeleton, muscles, organs, and skin. -
1st Trimester / 8 Weeks
Size: 0.06 inches Weight: 0.04 oz
Development: At this point, eyes begin to develop pigment, and genitals are forming too, although it's still too soon to know whether you're expecting a boy or a girl. These external features aren’t the only things developing — the internal organs are making strides, too. As the intestines form, they start to take up space in the umbilical cord because there’s not enough room in your baby’s abdomen yet. -
1st Trimester / 12 Weeks
Size: 2.1 inches Weeks: 0.49 oz
Development: At this point, your baby's hands are a little more developed than the feet, and the arms are longer than the legs. The little nailbeds that recently developed are starting to sprout fingernails and toenails, which will continue to grow to the tips of the fingers and toes during the next trimester. -
2nd Trimester / 16 Weeks
Size: 4.6 inches Weight: 3.5 oz
Development: Your baby's ears are closer to reaching their final position, and it is possible that your baby can hear sounds at this point, or in the next few weeks. -
2nd Trimester / 20 Weeks
Size: 6.5 Inches Weeks: 10.2 oz
Development: Rapid brain growth continues, particularly in the nerve centers dedicated to the senses. From time to time, loud noises may even wake him. Around this time your baby’s skin is thickening and layers of skin are forming as well. When you’re around 20 weeks of pregnancy, your baby’s digestive system starts to produce a greenish-black, sticky substance called meconium, which will accumulate in his bowels over the rest of the pregnancy. -
2nd Trimester / 24 Weeks
Size: 11.8 Inches Weight: 1.3 lb
Development: By 24 weeks, your baby’s inner ear is fully developed. This organ controls his sense of balance, and helps your baby sense if he’s right side up or not in the womb. Although your baby’s lungs are formed by this week, his lungs will only be ready to function normally in the outside world after they start producing a substance called surfactant. -
3rd Trimester / 28 Weeks
Size: 14.8 Inches Weight: 2.2 lbs
Development: Your little one is now able to open and close his eyes. He may even have some eyelashes! With his eyes open, your baby is now able to tell light from dark. Your baby’s brain is still developing, but the central nervous system has developed enough to allow your baby to begin to control his body temperature. When you’re 28 weeks pregnant, your baby’s position in the womb could be with his head facing down or with his buttocks pointed down. -
3rd Trimester / 32 Weeks
Size: 16.7 Inches Weight: 3.8 lbs
Development: He’s recently started shedding the lanugo — those fine hairs that covered your baby’s body — and most of it will be gone by now, though some babies are born with a little lanugo still on show. Your baby may be standing on his head now. You might feel him jostling into place as he flips. More and more fat is forming under your baby’s skin. This has slowly turned your baby’s skin from see-through to its current, opaque state. -
3rd Trimester / 36 Weeks
Size: 18.7 Inches Weight: 5.8 lbs
Development: He’s plumping up, becoming less wrinkled. All that growth means he doesn’t have quite as much room to move around at this point, because he’s now taking up most of the available space inside the amniotic sac. At this point, his skull bones are developed, but they haven’t yet fused together. This means they can move and overlap, allowing the head and body to pass through your cervix and pelvis a little more easily. -
3rd Trimester / 40 Weeks
Size: 20.2 Inches Weight: 7.6 lbs
Development: Your baby’s head has likely dropped lower into your pelvis, and his body is curled up tightly. He doesn't have much choice — it's pretty crowded in there. If your baby is in a breech position (rump down), your provider may attempt to turn him by placing firm pressure on your abdomen. If that doesn't work, your provider may discuss the possibility of a cesarean delivery with you. -
Birth
Size: 21 Inches Weight: 7.11 lbs
Development: His little body has been gaining fat up until this point so that he can more easily adjust to life outside the womb, and his liver, lungs, and brain are also still developing.