Chapter 12 Conception Pregnancy and Childbirth The Fertilization

Chapter 12 Conception, Pregnancy, and Childbirth

The Fertilization Process • Ovum released, drifts to fallopian tube – Oocyte viable ~ 12 - 24 hours after ovulation – Sperm viable ~ 12 - 48 hours • Capacitation: takes 6 -8 hours – biochemical changes in sperm cell – Enzymes allow it to penetrate egg’s outer membranes

Fertilization Process • Single sperm inside the oocyte cytoplasm • Oocyte swells • Sperm & Ovum nuclei release chromosomes – Divide to form the diploid zygote containing 23 pairs of chromosomes – Fertilization is now complete

Development of the Conceptus • Zygote undergoes cell divisions – Forms a blastocyst (100 cells) after 4 -5 days – Blastocyst implants in uterine lining on 6 th or 7 th day • Blastocyst becomes embryo after implantation in uterus • Embryo is called a fetus after 8 th week

Pregnancy Detection • Test for human chorionic gonadotropin (HCG) • Blood analysis • Home pregnancy tests • Early physical signs – Changes in cervix occur about 4 weeks after a missed period – Hegar’s sign – Labia change color, gaining purple hue

Changes During Pregnancy • Vary according to personality, feelings, and circumstances • Changes in relationships • Physical and emotional changes during each of the 3 trimesters • First trimester may include nausea, vomiting, fatigue

Complications and Dangers to the Fetus • Teratogens – Substances that cause defects in embryonic and fetal development • Infectious diseases – German Measles (rubella) – Group B streptococcus

Complications and Dangers to the Fetus • Sexually transmitted infections • Can be transmitted from pregnant woman to fetus, newborn, or infant • Chlamydia • Gonorrhea • Hepatitis B • HIV • Syphilis • Genital herpes

Complications and Dangers to the Fetus • Pregnancy after age 35 – Is more common as women wait to have children – Increased likelihood of chromosomal variation – Risk increases with increasing maternal age

Complications in Pregnancy • • Ectopic pregnancy Pregnancy-induced hypertension Premature births Delayed labor

Diagnosing Abnormalities of the Fetus • • Ultrasound Amniocentesis Chorionic villus sampling (CVS) Alpha-fetoprotein (AFP) screening

Ultrasound • High frequency sound waves determine size and position of fetus • Sonogram—picture • Estimates fetal age, guides during amniocentesis, checks for physical birth defects, evaluates complications during pregnancy

Amniocentesis • Amniotic fluid is withdrawn with needle inserted through abdominal wall • Detects: fetal abnormalities; Down’s syndrome, Turner’s syndrome, cystic fibrosis, spina bifida, sex and age • 0. 5 -2% chance of fetal death

Chorionic Villus Sampling (CVS) • Thin catheter inserted through abdomen or cervix into uterus to remove some chorionic villi • Detects: fetal abnormalities • Performed 9 -11 weeks

Alpha-fetoprotein Screening • Test run on mother’s blood • After 16 weeks of pregnancy • Detects: defects of spine, spinal cord, skull and brain

Pregnancy Loss • • Early pregnancy loss Miscarriage Infant mortality Coping with loss

Infertility • The inability to conceive after a year of unprotected intercourse or the inability to carry a child to term • Fertility issues are equally distributed among men and women • 1% of children in U. S. are the product of assisted fertility

Female Infertility • Physical causes – Pelvic Inflammatory Disease, an infection of the fallopian tubes or uterus • Hormonal & psychological causes – Hormone release may be atypical – Stress, anxiety, allergy • Environmental factors

Male Infertility • • Low sperm count Decrease of sperm motility Misshapen sperm Sperm duct blockage Ejaculatory difficulties Environmental factors Fertility begins dwindling after age 27

Infertility Treatment • Selective timing of sexual activity • Man wears boxer underwear • Woman lies with her back elevated following internal ejaculation

Medical Intervention • Fertility medications • Surgery • Artificial insemination

Assisted Reproductive Technology • • • In vitro fertilization - IVF Gamete intrafallopian transfer – GIFT Zygote intrafallopian transfer – ZIFT Surrogate motherhood Cloning Sex selection

Giving Birth: Labor and Delivery • Relaxin released by the placenta • Braxton Hick contractions

Labor: Stage 1 • • • Effacement: thinning of cervix Dilation: opening up of cervix Mucus plug is expelled Amniotic sac ruptures Contractions are regular and progressive • Transition

Labor and Delivery • Stage 2 – Begins when baby’s head moves into birth canal – Ends when baby is born – Vernix: waxy substance which may cover baby • Stage 3 – Afterbirth: placenta is expelled