Conception, Pregnancy, and Childbirth

HUMAN SEXUALITYDiversity in Contemporary AmericaFIFTH EDITION

Bryan Strong Christine DeVault Barbara W. Sayad William L. Yarber

C h a p t e r

McGraw-Hill © 2005 The McGraw-Hill Companies, Inc. All rights reserved.

12Conception, Pregnancy, and Childbirth

McGraw-Hill © 2005 The McGraw-Hill Companies, Inc. All rights reserved.

2 A Matter of Choice• Parenthood is now a matter of choice

– Increasing numbers of individuals and couples are choosing to remain child-free

• The birth of a wanted child is generally considered joyful– Some emotional pain and controversy

for others• Drugs, disease, malnutrition, familial chaos• Infertility

McGraw-Hill © 2005 The McGraw-Hill Companies, Inc. All rights reserved.

3 Fertilization Process• Ovum released from ovary, drifts to

fallopian tube– Oocyte viable ~ 12 - 24 hours after ovulation– Sperm viable ~ 12 - 48 hours – May be fertilized there if live sperm are present– If pregnancy proceeds normally, birth 266 days

later• Capacitation: takes 6-8 hours

– biochemical changes in sperm cell; release enzymes that allows it to penetrate egg’s outer membranes

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4 Fertilization Process• A single sperm is inside the oocyte

cytoplasm– An electrical reaction prevents any other sperm

from entering• Oocyte swells

– Detaches sperm that cling to outer layer• Sperm and ovum nuclei release

chromosomes– Chromosomes divide to form the diploid

zygote containing 23 pairs of chromosomes– Fertilization is now complete

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5 Development of the Conceptus• Zygote undergoes cell divisions

– Becomes a blastocyst of ~100 cells after 4-5 days

– Blastocyst implants in uterine lining on 6th or 7th day

• Blastocyst becomes embryo after implantation in uterus

• Embryo is called a fetus after 8th week

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6 Development of the Conceptus

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7 Pregnancy Tests• Test for human chorionic gonadotropin

(HCG)– A chemical secreted by the developing placenta

• Blood analysis• Home pregnancy tests• Early physical signs

– Changes in cervix occur about 4 weeks after a missed period

– Hegar’s sign• A softening of the uterus just above the cervix

– Labia change color, gaining purple hue

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8Changes That Occur During Pregnancy• Vary according to woman’s

personality, feelings, and circumstances– Changes in relationships– Physical and emotional changes during

each trimester• Three trimesters - each three months long• First trimester may include nausea,

vomiting, fatigue

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9 Complications of Pregnancy• Effects of teratogens

– Substances that cause defects in embryonic and fetal development• Toxins ingested by mother affect fetus

• Infectious diseases– German Measles (rubella)– Group B streptococcus

McGraw-Hill © 2005 The McGraw-Hill Companies, Inc. All rights reserved.

10 Complications of Pregnancy• Sexually transmitted diseases

– Can be transmitted from pregnant woman to fetus, newborn, or infant• Chlamydia• Gonorrhea• Hepatitis B• HIV• Syphilis• Genital herpes

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11 Complications in Pregnancy• Some complications:

– Ectopic pregnancy– Pregnancy-induced hypertension– Premature births – Operative delivery (Caesarian Section)

• Women age 40+ are more likely to experience complications in pregnancy

McGraw-Hill © 2005 The McGraw-Hill Companies, Inc. All rights reserved.

12Diagnosing Abnormalities of the Fetus• Ultrasound• Amniocentesis• Chorionic villus sampling (CVS)• Alpha-fetoprotein (AFP) screening

McGraw-Hill © 2005 The McGraw-Hill Companies, Inc. All rights reserved.

13 Ultrasound• High frequency sound waves

determine size & position of fetus• Sonogram - picture• Estimates fetal age, guides during

amniocentesis, checks for physical birth defects, evaluates complications during pregnancy

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14 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 & age

• 0.5-2% chance of fetal death

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15Chorionic Villus Sampling (CVS)• thin catheter inserted through

abdomen or cervix into uterus and some chorionic villi are sucked into tube

• Detects: fetal abnormalities• Performed ~ 9-11 weeks

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

cord, skull & brain

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17 Infertility• Infertility:

• the inability to conceive a child after a year of unprotected intercourse or the inability to carry a child to term

• Causes for women:– Pelvic Inflammatory Disease, an infection

of the fallopian tubes or uterus• Usually the result of an STI

– Hormonal & psychological causes• Glands might not release hormones to stimulate

ovulation• Stress may contribute to lowered fertility• A woman might be allergic to her partner’s sperm

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18 Infertility:• Physical causes for women,

continued:– Environmental factors

• Toxic chemicals, exposure to radiation therapy

– Natural factors• Beginning around age 30, women’s fertility

naturally begins to decline• ¼ of women are infertile by age 35

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19 Infertility• Causes for men:

– Low sperm count– Sperm motility decrease– Misshapen sperm– Sperm duct blockage– Ejaculatory difficulties– Environmental factors– Natural factors

• Men’s fertility begins dwindling after age 27

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20 Enhancing Fertility• Some simple, non-medical

techniques– Examples:

• Man stops wearing tight underwear• Woman lies on her back for an hour after

coitus

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21 Medical Intervention• Treatment successful in at least 50% of

cases– Fertility medications– Surgery– Procedures

• Intrauterine insemination (IUI) • Assisted reproductive technology

– In vitro fertilization (IVF) • Micromanipulation technique• Third-party methods

– Includes egg donation, sperm donation, and surrogate motherhood

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22 Labor and Delivery• 3 stages• Stage 1:

– Effacement: thinning of cervix– Dilation: opening up of cervix– mucus plug is expelled– amniotic sac ruptures– contractions are regular & progressive

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23 Labor and Delivery• Stage 2

– Begins when baby’s head moves into birth canal

– Ends when baby is born• Stage 3

– Placenta is expelled

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24 Choices in Childbirth• Hospital birth• Cesarean section• Prepared childbirth• Birthing rooms & centers• Home birth• Midwifery• Breast-feeding