FETAL DEVELOPMENT MONTH BY MONTH

Fetal Development Month by Month

Month One

  • Amniotic Sack Formation: A watertight sack forms around the fertilized egg, filling with fluid to cushion the developing embryo.

  • Placenta Development: The placenta, a round flat organ, develops to transfer nutrients from the mother to the baby and manage waste.

  • Facial Features and Circulation: A primitive face begins forming with developing mouth, lower jaw, and throat, while blood cells shape and circulation starts. The heart tube beats at 65 bpm by the end of week four.

  • Embryo Size: By the end of the month, the embryo is about a quarter inch long, smaller than a grain of rice.

Month Two

  • Facial Features: Continuing development of facial features like ears, which start as small skin folds.

  • Limb Development: Tiny buds for arms and legs form, with fingers, toes, and eyes developing.

  • Neural Tube Formation: The neural tube, which becomes the brain, spinal cord, and central nervous system, is well formed; digestive tract and sensory organs begin developing.

  • Bone Development: Cartilage starts to be replaced by bone, and the head is disproportionally large.

  • Size and Weight: By the end of the second month, the baby is about an inch long and weighs around one-thirtieth of an ounce, with a detectable heartbeat by six weeks.

  • Transition from Embryo to Fetus: After eight weeks, the developing baby is referred to as a fetus.

Month Three

  • Full Organ Formation: By the end of the month, all organs and extremities are formed and continue to mature; the baby can close its fists and mouth.

  • Nail Development: Fingernails and toenails begin forming, with early tooth development occurring.

  • Reproductive Organ Formation: The reproductive organs develop, but gender identification via ultrasound is difficult at this stage.

  • Functioning Systems: The circulatory and urinary systems start working, and the liver produces bile.

  • Size and Weight: The fetus measures about four inches long and weighs approximately one ounce, with a lower miscarriage risk after this month.

Month Four

  • Audible Heartbeat: The fetus's heartbeat can be heard using a Doppler instrument.

  • Development of Features: Well-defined fingers and toes, formation of eyelids, eyebrows, eyelashes, and initial hair appear, along with dense teeth and bones.

  • Physical Movements: The baby can suck its thumb, yawn, stretch, and make facial expressions.

  • Fully Developed Reproductive Organs: Gender can often be determined through ultrasound.

  • Size and Weight: By the end of the month, the fetus is about six inches long and weighs around four ounces.

Month Five

  • Quickening: The mother may start feeling baby movements, known as quickening.

  • Hair and Skin Development: Hair grows on the head, with lanugo (soft hair) covering the back and shoulders, and a protective coating of vernix caseosa covers the skin.

  • Size and Weight: The fetus measures about ten inches long and weighs between half to one pound by the end of the month.

Month Six

  • Skin Appearance: The skin appears reddish and wrinkled, revealing veins beneath a translucent skin layer.

  • Eye Development: Eyelids open and the baby starts responding to sounds; muscle jerks can indicate hiccups.

  • Survival Potential: A fetus born prematurely at this stage may survive with intensive care; by the end of the month, it is about twelve inches long and weighs around two pounds.

Month Seven

  • Body Fat Development: The fetus accumulates body fat and can change positions; fully developed hearing allows responses to stimuli like sound and light.

  • Amniotic Fluid Levels: The amniotic fluid begins to decrease.

  • Size and Weight: At the end of this month, the fetus is about fourteen inches long and weighs between two to four pounds, with a high survival rate if born prematurely.

Month Eight

  • Brain Development: Rapid brain development occurs; the baby can see and hear, with ongoing maturation.

  • Lung Immaturity: Although most internal systems are well developed, the lungs may still require growth.

  • Size and Weight: By the end of the eighth month, the fetus is approximately eighteen inches long and may weigh up to five pounds.

Month Nine

  • Final Preparations for Birth: The lungs near full development, and reflexes become coordinated; the baby can blink, turn its head, and respond to sound and touch.

  • Movement Decrease: Fetal movement may lessen due to confinement within the womb, and the baby's position shifts in preparation for delivery.

  • Size and Weight: The baby is about eighteen to twenty inches long and weighs around seven pounds, ready to be born.