First, Second and Third Trimesters Fetal Development First, Second and Third Trimesters

Definition: Trimester One of the three periods of approximately 3 months into which pregnancy is divided. The first trimester includes the time from the first day of the last menstrual period to the end of 12 weeks. (conception – 12 weeks) The second trimester, closer to 4 months in length than 3, extends from the twelfth to the twenty-eighth week of gestation. (12 – 28 week) The third trimester begins at the twenty-eighth week and extends to the time of delivery. (28 – delivery)

1st Month

1st Month Milestones Arms and legs begin to form The brain and spinal cord begin to form The heart and lungs begin to develop. The heart begins to beat near the end of this month

First Trimester Week 2: Conception is the moment at which the sperm penetrates the ovum. Once fertilized it is called a zygote, until it reaches the uterus 3-4 days later. Fact: The zygote contains all of the genetic information (DNA) needed to become a baby. Week 4: The embryo may float freely in the uterus for about 48 hours before implanting. Upon implantation, complex connections between the mother and embryo develop to form the placenta.

Month - 2

2nd Month Milestones Eyelids form, but remain closed The inner ear begins to develop Bones appear Ankles, wrists, fingers and toes form The genitals begin to develop By the end of month, all major body systems have begun to develop

First Trimester (cont.) Week 6: The embryo is about 1/5 of an inch in length. A primitive heart is beating. Head, mouth, liver, and intestines begin to take shape. 7 weeks - Brain has the first detectable brain waves, muscles develop and get stronger

Month - 3

3rd Month Milestones Twenty buds for future teeth appear All internal parts are formed, but are not fully developed Soft nails begin to form The intestines begin to form Skin is almost transparent Hand are more developed thatn feet Arms are longer than legs

First Trimester (cont.) Week 10: The embryo is now about 1 inch in length. Facial features, limbs, hands feet fingers and toes become apparent. The nervous system is responsive and many of the internal organs begin to function. The end of the 10th week of pregnancy marks the end of the "embryonic period" and the beginning of the "fetal period." 8 weeks - Eyes are well-developed, Fingers lengthen while distinct grooves (digital rays) form between the fingers

12 Weeks 12 weeks - Fetus begins to move around, though the mother cannot yet sense these movements.

Month - 4

4th Month Milestones Eyebrows, eyelashes, and fingernails form Arms and legs flex External sex organs are formed The placenta is fully formed The outer ear begins to develop The fetus can swallow and hear The neck is formed Kidneys are functioning and begin to produce urine

Second Trimester Week 14: The fetus is now 3 inches long and weighs almost an ounce. The muscles begin to develop and sex organs form. Eyelids, fingernails, and toenails also form. The child's spontaneous movements can be observed.

14 Weeks 14 weeks - Fetus is more flexible with ability to move head, mouth, lips, arms, wrists, hands, legs, feet, and toes

Second Trimester (cont.) Week 18: The fetus is now about 5 inches long. The child blinks, grasps, and moves her mouth. Hair grows on the head and body. Fetus has phases of sleep and waking and may prefer a favorite sleep position, temporary hair called lanugo appears on the head.

Month - 5

5th Month Milestones The sucking reflex develops The fetus sleeps and wakes regularly Nails grow to tips of fingers The Gallbladder begins to produce bile, which is needed to digest nutrients In Girls, the eggs have formed in ovaries In Boys, the testicles begin to descend from the abdomen into the scrotum

Second Trimester (cont.) 20 weeks -  Fetus may suck on thumb. Extremely rapid brain growth; eyebrows and scalp hair become more visible and fetus blinks more often

Second Trimester (cont.) Week 22: The fetus now weighs approximately 1/2 a pound and spans about 10 inches from head to toe. Sweat glands develop, and the external skin is no longer transparent

Month - 6

6th Month Milestones Real hear begins to grow The brain is rapidly developing The eyes begin to open Finger and toe prints can be seen The lungs are fully formed, but not yet functioning

Third Trimester 24 weeks - Fetal brain waves begin to activate auditory and visual systems, both mouth and lips show more sensitivity. Eyes respond to light, while ears respond to sounds originating outside uterus.

Month -7

7th Month Milestones The eyes can open and close and sense changes in light The fetus kicks and stretches The fetus can make grasping motions and responds to sound

Third Trimester (cont.) Week 26: The fetus can now inhale, exhale and even cry. Eyes have completely formed, and the tongue has developed taste buds. Under intensive medical care the fetus has over a 50% chance of surviving outside the womb.

Month - 8

8th Month Milestones Bones harden, but the skull remains soft and flexible for delivery The different regions of the brain are forming Taste buds develop and the fetus can taste sweet and sour The fetus may now hiccup

Third Trimester Week 30: The fetus is usually capable of living outside the womb and would be considered premature at birth.

Month - 9

9th Month Milestones The fetus usually turns into a head-down position for birth The skin is less wrinkled The lungs mature and are ready to function on their own Sleeping pattern develop The fetus will gain about ½ pound per week this month

Third Trimester Cont… Week 40:This marks the end of the normal gestational period. The child is now ready to live outside of his mother's womb.

Fetal Development Vocabulary Progesterone: hormone that changes the lining of the uterus and prevents the ovaries from releasing any more eggs Fertilization: union of an ovum and sperm; also called conception Estrogen: Any of a group of steroid hormones that promote the development and maintenance of female characteristics of the body Zygote: a fertilized egg Chromosome: a threadlike structure that carries genes; 23 male/23 female Fetus: a developing human from usually two months after conception to birth

Vocabulary continued… Umbilical Cord: is a robe-like structure that connects the embryo to the placenta; the area in which the mother’s blood caries nutrients and oxygen to the fetus Afterbirth: the placenta and fetal membranes that are expelled after delivery Gene: is a unit of hereditary material Oxytocin: referred to as the “love” hormone Progesterone: hormone that changes the lining of the uterus and prevents the ovaries from releasing any more eggs

Facts: Each year in the United States, there are approximately six million pregnancies. This means that at any one time, about 4% of women in the U.S. are pregnant. Only 25% of couples actively trying to conceive will experience pregnancy within the woman’s first cycle. However, 90% of couples will achieve pregnancy within the first 12 months of actively trying. Approximately 10% of pregnancies will end in miscarriage. Many miscarriages often occur before a woman even knows she is pregnant. Just under 500,000 babies are born each year in the U.S. to teenage mothers The average size of a full-term baby in the U.S. is 8 pounds. This is an increase from an average size of 6 pounds 30 years ago.

Facts continued…. The largest baby ever born weighed in at over 23 pounds but died just 11 hours after his birth in 1879. The largest surviving baby was born in October 2009 in Sumatra, Indonesia and weighed an astounding 19.2 pounds at birth Approximately one in three babies in the United States is now delivered by cesarean section. The number of cesarean sections in the U.S. has risen nearly 46% since 1996 Fewer than 10% of babies are born on their exact due date, 50% are born within one week of the due date, and 90% are born within two weeks of the date