16th week of pregnancy: the baby about the size of small grapefruit:. Your baby is about 12 cm long and weighed about 100 g. Facial muscles of a baby has developed enough so it is actively building grimaces, frowns and smiles in the womb.
During the 16th weeks of pregnancy the baby’s eyes are already located in their places in front of the head, the ears continue moving, the body becomes more proportional.
Baby’s neurones are actively growing, their number is increased by 5,000 units per second, and the adrenal glands are already producing the required amount of hormones. The ovaries of the girls fall into the pelvic area, the fallopian tubes, uterus and vagina are already formed. In boys, the external genitalia are formed, but the testicles are still in the abdominal cavity.
Henceforth, the bone marrow of a baby is responsible for hematopoiesis, and at this period the blood composition of a baby has already formed: red blood cells, monocytes and lymphocytes are present, it is possible to determine the blood group and Rh factor. The fetal hemoglobin is produced, usual hemoglobin appears in the baby’s blood in six months after the birth only, and the heart is active, every second pumping about 25 liters of blood.
The bone skeleton of a baby continues to strengthen, legs become more developed, nails on fingers are almost fully formed. The liver is beginning to perform its digestive functions. The stomach, intestine and gall bladder gradually proceed to their direct responsibilities too. For example, there appears the first content that yet consists essentially of bile in the intestine of a baby. It is original feces, dark-green or black-green meconium.
At this period the kidneys and the bladder of a baby are carrying their missions: the baby urinates every 45 minutes. Urine enters the amniotic waters which are updated throughout the day (about ten times a day), allowing them to maintain a stable chemical composition required for the successful development of the fetus. Now the amount of amniotic fluid (amniotic fluid) is about 250 g.
The umbilical cord which connects mom and a baby is very durable and flexible and is able to withstand loads up to 5-6 kg. Its length at this gestational age is already about 40-50 cm and about 2 cm in diameter.