Facts about an unborn baby

• The average length of a full-term pregnancy is 38 weeks. A figure of 40 weeks is often used by obstetricians, but this is actually the time between the first day of the last menstrual period and childbirth. On average, the first day of the last menstrual period occurs 2 weeks before fertilization. [1, 2, 3]
• Fertilization normally takes place within one day of intercourse, but six days later it can still take place.[4, 5] At fertilization, the genetic composition of a pre-born human is formed.[6] It is this genetic information determines the child’s gender, eye and hair colour, facial features, and influences characteristics such as intelligence and personality.[7] Genetically speaking, with the exception of identical twins,[8, 9] once a pre-born human is conceived, the odds against the same one being conceived again by the mother are greater than 10600 to one.[10, 11]
• Three weeks after fertilisation or five weeks after the last menstrual period (LMP), the eyes and spinal cord are visible and the developing brain has two lobes.[12, 13]
• Four weeks after fertilisation (6 weeks after LMP), the heart is beating and the circulatory system is established.[14] Specific brain components and some internal organs such as the lungs are beginning to develop and can also be identified.[15]
• Seven weeks after fertilisation, the muscles and nerves begin working together. When the upper lip is tickled, the arms move backwards.[16] During this period, the cerebrum has divided into hemispheres.[17]
• Nine weeks after fertilisation, more than 90% of the body structures found in a full-grown human are already present. It is at this period, that the embryo is referred to as a fetus. This dividing line was chosen by embryologists because from this point forward, most development involves growth in existing body structures instead of the formation of new ones.[18, 19] The pre-born human moves body parts without any outside stimulation.[20]
• Ten weeks after fertilisation, the brain and spinal cord are completely formed. The heart now pumps blood to the entire body.[21] The whole body is sensitive to touch except for portions of the head. The pre-born human will start making facial expressions.[22]
• Twelve weeks after fertilisation, electrical signals from the nervous system are measurable. After an abortion, efforts to suckle will sometimes be observed.[23, 24]
• Fourteen weeks after fertilisation, the pre-born human is making coordinated movements with the arms and legs.[25]
• Sixteen weeks after fertilisation, eye movements are already being observed.[26]
• Eighteen weeks after fertilisation, the portion of the brain responsible for functions such as reasoning, memory and language (the cerebral cortex) possesses the same number of nerve cells as an adult. Pain sensory receptors have also spread to all portions of the skin and mucous membranes.[27, 28]
• Twenty weeks after fertilisation, the pre-born human sleeps, awakes and can hear sounds as well.[29]
• Twenty-four weeks after fertilisation, the blink-startle reflex and taste buds are functional. The pre-born human will swallow more amniotic fluid if a sweetener is added to it.[30, 31] The grip is strong enough to hold onto an object that is moving up and down.[32] If born and given specialized care, the survival rate of the child is more than 80%.[33]
• Twenty-eight weeks after fertilisation, if the preborn is exposed to an 85 decibel noise while sleeping (about as loud as a blender), he/she exhibits the “motor behaviours that accompany the crying state.” [34, 35] Premature infants born at this time are more sensitive to pain than infants who are born at 38 weeks, and infants who are born at 38 weeks are more sensitive to pain than infants at 3-12 months after birth.[36, 37] If born and given specialized care, the survival rate is higher than 95%.[38]
• Thirty-eight weeks after fertilisation. This is the average point in time when humans are born. At birth, the medical classification changes from a foetus to a neonate.[39, 40]