🫦Intro to Human Sexuality Unit 8 – Conception to Birth: Human Reproduction

Key Concepts and Terminology

• Conception occurs when a sperm fertilizes an egg, usually in the fallopian tube
• Zygote is the fertilized egg that contains genetic material from both parents
• Embryo refers to the developing human during the first 8 weeks after conception
  • Undergoes rapid cell division and differentiation
  • Major organs and systems begin to form
• Fetus is the term used for the developing human from the 9th week until birth
• Gestation is the period of time from conception to birth, typically around 40 weeks
• Trimesters divide the pregnancy into three periods, each lasting about 13 weeks
  • First trimester: conception to week 12
  • Second trimester: weeks 13 to 28
  • Third trimester: week 29 until birth
• Placenta is an organ that develops during pregnancy to provide oxygen and nutrients to the fetus and remove waste products
• Umbilical cord connects the fetus to the placenta, allowing for the exchange of nutrients and waste

The Biology of Conception

• Ovulation occurs when a mature egg is released from the ovary, typically once per menstrual cycle
• Sperm must travel through the cervix, uterus, and fallopian tubes to reach the egg
  • Sperm can survive in the female reproductive tract for up to 5 days
• Fertilization happens when a single sperm penetrates the outer layer of the egg
  • Triggers changes in the egg's surface to prevent other sperm from entering
• The fertilized egg, now called a zygote, contains 46 chromosomes (23 from each parent)
• The zygote undergoes rapid cell division as it travels down the fallopian tube towards the uterus
• Implantation occurs when the zygote attaches to the uterine wall, usually 6-12 days after fertilization
  • Marks the beginning of pregnancy
• If fertilization does not occur, the unfertilized egg disintegrates, and the uterine lining is shed during menstruation

Stages of Embryonic Development

• Week 1: Fertilization and implantation occur
• Week 2: The embryo develops into a blastocyst, a hollow ball of cells
  • The inner cell mass will become the embryo, while the outer cells form the placenta
• Week 3: The embryo undergoes gastrulation, forming three distinct cell layers (ectoderm, mesoderm, and endoderm)
  • Each layer gives rise to specific tissues and organs
• Week 4: The neural tube, which will become the brain and spinal cord, begins to form
• Week 5: The heart starts to beat, and early structures of the eyes and ears develop
• Week 6: Arm and leg buds appear, and the embryo begins to take on a more recognizable human shape
• Week 7: The embryo is about 1 cm long, and the brain continues to develop rapidly
• Week 8: The embryonic period ends, and the fetal period begins
  • All major organs and systems are present, but not fully developed

Fetal Growth and Milestones

• First trimester (weeks 1-12):
  • Rapid growth and development of major organs and systems
  • By the end of week 12, the fetus is about 6 cm long and weighs around 14 grams
• Second trimester (weeks 13-28):
  • Fetal growth accelerates, and the fetus begins to move and respond to stimuli
  • By week 20, the fetus can hear and swallow
  • By the end of week 28, the fetus is about 35 cm long and weighs around 1 kg
• Third trimester (weeks 29-40):
  • Fetus continues to grow and gain weight rapidly
  • Organs mature and prepare for life outside the womb
  • By week 36, the fetus is considered full-term and may engage in the pelvis in preparation for birth
  • At birth, the average newborn is about 50 cm long and weighs around 3.5 kg

Maternal Changes During Pregnancy

• Hormonal changes, such as increased levels of estrogen, progesterone, and human chorionic gonadotropin (hCG)
  • Support fetal development and prepare the body for childbirth
• Uterus expands to accommodate the growing fetus
  • Can increase up to 20 times its pre-pregnancy size
• Breasts enlarge and prepare for milk production
• Cardiovascular changes include increased blood volume and cardiac output
  • Support the increased metabolic demands of pregnancy
• Respiratory changes, such as increased tidal volume and decreased residual volume
  • Ensure adequate oxygen supply for the mother and fetus
• Gastrointestinal changes, such as decreased motility and increased risk of heartburn and constipation
• Weight gain due to the growth of the fetus, placenta, and maternal tissues
  • Average weight gain is 11-16 kg for a single pregnancy

Potential Complications and Health Concerns

• Miscarriage is the spontaneous loss of a pregnancy before the 20th week
  • Most common in the first trimester
  • Can be caused by chromosomal abnormalities, hormonal issues, or maternal health problems
• Ectopic pregnancy occurs when the fertilized egg implants outside the uterus, usually in the fallopian tube
  • Can be life-threatening if not treated promptly
• Gestational diabetes is a type of diabetes that develops during pregnancy
  • Can increase the risk of complications for both the mother and the fetus
• Preeclampsia is a condition characterized by high blood pressure and protein in the urine
  • Can lead to serious complications if left untreated
• Placental abruption occurs when the placenta partially or completely separates from the uterine wall before delivery
  • Can cause severe bleeding and may require immediate medical attention
• Preterm labor is labor that begins before the 37th week of pregnancy
  • Can lead to premature birth and associated health risks for the newborn

Birth Process and Types of Delivery

• Labor is the process by which the fetus is expelled from the uterus
  • Characterized by regular uterine contractions and cervical dilation
• Stages of labor:
  • First stage: Onset of regular contractions until the cervix is fully dilated (10 cm)
  • Second stage: Fully dilated cervix until the baby is delivered
  • Third stage: Delivery of the baby until the placenta is expelled
• Vaginal delivery is the most common type of birth
  • The baby is delivered through the birth canal
  • Can be assisted with forceps or vacuum extraction if necessary
• Cesarean section (C-section) is a surgical procedure to deliver the baby through incisions in the abdomen and uterus
  • May be planned or emergency, depending on maternal or fetal indications
• Water birth involves delivering the baby in a pool of warm water
  • Can help with pain management and relaxation during labor
• Home birth is when a woman chooses to give birth at home, usually with the assistance of a midwife
  • Requires careful planning and risk assessment

Ethical and Social Considerations

• Assisted reproductive technologies (ART), such as in vitro fertilization (IVF), raise ethical questions about the creation and selection of embryos
• Surrogacy involves a woman carrying and delivering a baby for another person or couple
  • Can be complex legally and emotionally
• Abortion is the termination of a pregnancy
  • Raises ethical debates about the rights of the fetus and the autonomy of the pregnant woman
• Maternal leave policies vary by country and employer
  • Can impact a woman's decision to start a family and her ability to balance work and family responsibilities
• Access to prenatal care and education can vary based on socioeconomic status and geographic location
  • Can lead to disparities in maternal and fetal health outcomes
• Cultural and religious beliefs can influence decisions about family planning, prenatal care, and childbirth practices
• Postpartum support is important for the physical and emotional well-being of new mothers
  • Includes access to healthcare, social support, and resources for adjusting to parenthood