PERIODS OF PREGNANCY

First-fourth pregnancy week
Your body is ready for egg laying (ovulation) following the end of your menstruation period. Ovulation occurs in women between 11-19^th days beginning from the first day of menstruation. Sperm cells oscillating to vagina with sexual relationship reach to uterus by passing through uterus mouth and then oviducts, and this sperm generates zygote by combining with mature ovule. Zygote divides while passing through oviduct and forms morula. Morula obtains the name of blastocyst when it reaches to uterus. Blastocysts has hold on uterus wall after 6-10 days after fertilization and the embryonic period starts beginning from this stage. This period is the phase when brain and nervous system, spine, heart and circulation system, stomach and bowels start to develop.




Fifth pregnancy week
Arm and leg limbs emerge. Heart beatings can be monitored on ultrasonography. Placenta and navel cord develops. Placenta starts to secrete some hormones significant for pregnancy. Navel cord is required for oxygen and food transfer for baby and for removal of wastes. Moreover, structures which will form eyes and ears appear in this period.

Sixth pregnancy week
Development of lung, nose, chin and palate starts. Arms and legs continue to develop. More complex parts of brain start to develop in this period. Lens structure appears on eyes. Nostrils are formed. Development of intestines continues. Intestines locate in navel cord outside body of baby at first. Pancreas starts to develop in this period.


Seventh pregnancy week
All vital organs of embryo which is equal to an aspirin tablet in size continue to develop during this period. Hair follicles, eye lids and tongue start to develop. Elbows and fingers-toes become visible; corpus starts to flatten. Eyes, ears and nose become clear. Teeth development starts below gums.

Eight pregnancy week
Internal and external ear development continues. Cartilage and bone formation starts. Intestines relocate from navel cord towards inside of abdomen. Embryonic period comes to an end after this week.

Ninth-thirteenth pregnancy week
Baby gets into motion during about ninth week, but this is not noticed by mother. Baby can motion fingers again during these weeks. Placenta function actually starts in this period and continues. Fingers and toes separate from each other in about tenth week. Nails start to develop. Genital organs of fetus start to differentiate towards appropriate sex as male or female, but sex of baby cannot be clearly seen on ultrasonography yet. Amnion fluid required for kidney function starts to accumulate. Eyelids close in this period and remain closed until 28^th week. By this way, iris development and determination of eye color are ensured. Vocal cords start to develop. Eyes and ears relocate toward their normal places. Liver and pancreas start to function in about twelfth week. Inhale-exhale movements start in about thirteenth week. Baby’s neck gets longer a bit and hands become more functional. Size of fetus head is equal to the half of baby’s total size during these weeks.

Fourteenth-sixteenth pregnancy week
Baby’s skin is thin and transparent, and skin surface is covered with fuzzes called as lanugo during these weeks. Thyroid glands develop and start to secrete hormone. Prostate gland develops in male babies, and ovariums relocate towards below part of abdomen in female babies. You can feel motions of baby in these weeks, because it can take many movements including thumb sucking, catching, frowning, and grimace. Legs and arms continue to lengthen. Fingers and toes grow up. Little bones in middle ear start to develop which is required for hearing in the future. Regular thoracic cage movements appear in this period, baby swallows and vomits amniotic fluid. Fat accumulation on sub surface skin starts in sixteenth week. Fingerprint also starts to develop in this period.

Seventeenth-twentieth pregnancy week
Baby’s movements become more perceivable during these weeks. Eyebrows and eyelashes develop. The substance called vernix which looks like cheese, protects baby from amniotic fluid in mother’s abdomen and cover the whole skin starts to be formed. Small air vesicles start to be formed in lungs. Heart sounds of baby can be heard above abdomen of mother with stethoscope. Sleeping-waking periods start just like a new born baby during about nineteenth week. Nerves start to be covered with the substance called as myelin which provides signal transmission. Hairs become distinct, milk teeth develop and kidneys start to function. Uterus development starts in female babies. Development of baby continues more rapidly after twentieth week. Muscle development is evident. Transfer of immunity cells which transits from mother to baby and continue to protect baby during 6 months following birth start. Nerves having tasks like smelling and tasting develop in special parts of brain. Baby gives some light responses to sounds in these weeks.

Twenty first-twenty third pregnancy week 
lanugo covers the whole body surface during these weeks and fetus starts to gain the outlook of a new-born baby since sub surface skin fat thickness increases. Development of eyes complete. Liver and pancreas complete their development. White blood cells (leucocytes) required for defense of body against diseases start to develop. Large intestine movements start with the increase in swallowing movements. Vagina development starts in female babies. Weight of baby reaches up to 360 grams in about twenty first week. Eyebrow and eyelash development completes in about twenty second week. Baby starts to hear any sound better. Brain development accelerates. Testicles start to come down towards its place in male babies, production of sperm cells and testosterone oscillation starts.

Twenty four-twenty seventh pregnancy week
Tongue pimples which provide tasting starts to develop during these weeks. Sweat glands are formed. Lung development accelerates. Blood vessels in lungs develop in about twenty fifth week. Nerves surrounding mouth and on lips become more sensitive. Capturing and grasping reflexes develop more. Weight of baby is about 750 grams in the twenty sixth week. Lungs start to oscillate the substance called surfactant which ensure enlargement during confinement. Brain development accelerates in twenty seventh week. Baby becomes more sensitive against sounds since nerve structures in ear complete their development. Breathing exercises made by baby in the amniotic fluid makes baby ready for inhaling and exhaling after birth. Eyelids open and baby starts to notice light-darkness.

Twenty eight-thirty second pregnancy week
Fat storage continues in these weeks even though it is not as intensive as in last weeks of pregnancy. Baby puts on weight due to the increase in muscle and bone mass and body ratios of baby change. Lungs continue rhythmic inhaling-exhaling actions even though they are not completely mature yet. Bones are still soft although bone development completes. Brain starts to control inhaling-exhaling actions and boy temperature during about twenty ninth week. Baby can revolve from one side to another. It becomes more sensitive to light, smells and tastes. Eye movements accelerate and diversify in about thirteenth week, teardrop generation starts. Bone marrow starts production of red blood cells (erythrocyte). Calcium, iron and phosphor which ensure hardening in bones stat to accumulate in bones. Weight of baby is about 1500 grams. All organs except lungs complete their development in this period.

Thirty three-thirty sixth pregnancy week
Fetus relocate towards bottom part of the abdomen in a way head is downward for preparation to birth. Rapid development in brain and nervous system continues. Rapid weight increase continues. Lanugo hairs disappear and skin becomes more tight and mat; therefore baby more resembles a new-born baby. Twinkling reflex starts. Weight of baby is about 2100 grams in thirty fourth week. Body temperature can be controlled better due to rapid fat accumulation on arms and legs after this week. Since baby relocates towards birth canal after thirty sixth week, respiration of mother will ease but walking may become difficult.

Thirty seventh-fortieth pregnancy week
Weight of baby is about 2800 grams in the thirty seventh week. Baby is ready for birth after thirty eight week. Meconium which is formed due to intestine actions of baby and means the first evacuation of baby in birth accumulates on intestines. Since baby fills the whole uterus, a decline occurs in its movements. Little breast sprouts appear in both sexes. All organs except lungs have completed their development in this period, development of lungs complete with birth.