Fertilization, Pregnancy, and Labor and Delivery

Ch. 29

Pregnancy by Weeks

• Doctors and midwives track pregnancy by weeks.

• A typical pregnancy and full-term is 40 weeks• The weeks are counted from the first day of

your last period– This means that during week 1, you are not

technically pregnant yet

Embryonic Period

• Fertilization (week 2)• Sperm and egg unite• 300 million sperm make it into the vagina• Only 2 million reach the cervix• Only 200 reach the egg in the fallopian tube• Fertilization occurs 12-24 after ovulation• Pregnancy is most likely during a 3-day window– 2 days before ovulation to 1 day after ovulation

Fertilization

• Videos

After Fertilization

• Cell is called a zygote• Cleavage– Mitotic divisions of cells– 1 to 2 to 4 to 16 (3 days)

• Implantation– Zygote implants into wall of uterus– Occurs 6 days after fertilization

After Fertilization

Twins

• Twins– Dizygotic (fraternal) – two sperms, two eggs– Monozygotic (identical) – 1 egg, 1 sperm, divides

within first 8 days– After 8 day division – conjoined twins

• Ectopic Pregnancy– Development of embryo outside uterus– Can happen in fallopian tube or ovary– Pregnancy cannot continue

Summary of second week

Review

• What occurs in the first 3 days after fertilization?

• Describe the difference between fraternal and maternal twins.

• What occurs during the first week after fertilization?

By the end of month 1

• Baby is ¼ inch long, size of poppy seed

• Heart, digestive system, backbone, and spinal cord are beginning to form

• Placenta develops

By the end of month 2

• Heart is functioning• Eyes, nose, lips, tongue,

ears, teeth are forming• Baby is moving, but

mom can’t feel it yet• Arm and leg buds

appear• Size of a kidney bean• http://www.babycenter.com/2_insid

e-pregnancy-weeks-1-to-9_10302602.bc

By the end of month 3

• Arms, hands, fingers, legs, and toes are fully formed

• Nails form, hair grows• Most organs are fully

formed• Reflexes – opening

mouth, sucking, grasping• Urinating – drinks urine• Size of a lime

By the end of month 4• Genitals are developed• Skin is pink and covered in

soft hair• Can suck thumb• Facial expressions• “breathing” – moves

amniotic fluid into lungs• Taste buds form, eyes can

sense light but are still closed

• Size of avocado• http://www.babycenter.com/2_inside

-pregnancy-weeks-1-to-9_10302602.bc

By the end of month 5 (1/2 way)• Baby weighs 1 lb. (size of banana)• Mommy can feel baby move• Internal organs mature• Eyebrows, eyelids, eyelashes

appear• Cartilage is turning to bone• Nerves are becoming myelinated• Baby can hear voices or loud

noises• Produces meconium• http://www.babycenter.com/2_inside-pregna

ncy-weeks-1-to-9_10302602.bc

By the end of the 6th month

• Eyes can open• Skin is covered in waxy

vernix to prevent pickling in amniotic fluid

• Baby hiccups – mom can feel it

• Mom can see baby move in belly

• Baby is gaining weight

By the end of the 7th month

• If baby is born now, he could survive but need special care

• Hair is growing• Baby is gaining fat• Baby sleeps and is awake• Baby can blink and see

light• http://www.babycenter.com/2_inside-pre

gnancy-weeks-21-to-27_10312242.bc

By the end of the 8th month

• Brain grows• Weight gain is rapid• Organs are fully developed

except lungs• Skin is less wrinkly, baby is

filled out

By the end of the 9th month

• Baby has turned head down to prepare for birth

• Lungs are fully developed• http://www.babycenter.com/2_inside-pregnancy-we

eks-21-to-27_10312242.bc

Review

• Summarize the events that take place in each month of pregnancy. Focus mainly on organ development.

Prenatal Testing

• Doppler – used to listen to baby’s heartbeat• Ultrasound – used to get accurate fetal age,

check for proper growth, determine fetal position, identify multiple pregnancies

Ultra sounds pics here!

Amniocentesis• Invovles withdrawing some amniotic fluid and analyzing fetal

cells• Can detect genetic disorders

– Down syndrome– Hemophilia– Tay-Sach’s disease– Sickle-cell disease

• Ultrasound is used to prepare• Needle is inserted through mother’s abdomen and into

amniotic cavity• Fluid is withdrawn and analzyed

Chorionic Villi Sampling (CVS)

• Catheter is guided through vagina and cervix into chorionic villi of placenta

• Can detect same disorders as amniocentesis• Advantages– Can be done earlier– Test results are quicker– Abdominal penetration isn’t required

• Disadvantage – increased risk for miscarriage (1-2%)

Early Pregnancy Test (EPT)

• Detect tiny amounts of human chorionic gonadotropin (hCG) in urine

• False-positives are rare – if you have the hormone, you are pregnant

• False-negatives are more common – testing too soon

Labor

• Contractions can begin weeks before delivery• Sometimes the mother can’t feel them• Braxton-Hick’s contractions – tightening of the

muscles surrounding the baby, but not uterine• Induced by oxytocin• “false” labor – when contractions are irregular, no

dilation, no mucus discharge (plug)• “true” labor – mucus plug, contractions are regular,

walking intensifies contractions

Labor

• 3 stages– Stage of dilation (6-12) hours• Starts from start of labor to complete dilation (10 cm)• Amniotic sac breaks (water)

– Stage of expulsion (10 min. to several hours)• From complete dilation to delivery of baby

– Placental stage (5-30 min.)• When placenta is delivered

Labor

C-Section

• Cut through abdominal wall and lower uterus

• Baby is removed• Stitches to close up incision• Done because:– Woman is not progressing– Baby is not in correct position– Mother’s body could not handle

delivery (blood pressure, etc.)

Newborn

• Often have cone-shaped heads because of trip through birth canal

• Suction is used to clear nose and mouth for breathing

Videos

• http://www.babycenter.com/2_inside-pregnancy-weeks-21-to-27_10312242.bc