21.3

Conception, Pregnancy, and Birth

Genetics and Traits

• Genes from both biological parents influence a person's traits
• Chromosomes from each parent carry genetic material that determines characteristics
• 22 pairs of chromosomes possess similar genetic material, which influences traits such as eye color, hair color, and risk of diseases
• Multiple genes influence many characteristics, with some genes being dominant and others being recessive

Conception

• Humans reproduce through sexual intercourse, where sperm enter the vagina and swim to the fallopian tube to fertilize an egg
• The moment of sperm and egg combination is called conception
• A single sperm fertilizes an egg, and a barrier forms to prevent additional sperm from entering

In Vitro Fertilization (IVF)

• A technology developed to help couples conceive, involving hormone stimulation, egg fertilization, and embryo insertion into the uterus
• IVF can help people conceive children, passing on genes from the mitochondria

Pregnancy

• Human gestation is approximately 9 months, with most babies born 36-40 weeks after fertilization
• Pregnancy can be divided into stages, and a person's behaviors during pregnancy influence the health of the developing baby

Stages of Prenatal Development

• Germinal Stage: Lasts about 2 weeks, from conception to implantation, where the zygote divides rapidly into many cells
• Embryonic Stage: Lasts about 6 weeks, where the embryo develops tissues and organs, and systems take shape
• Fetal Stage: Begins at the 9th week, where the fetus grows and develops, lasting until birth

Pregnancy Complications

• Ectopic Pregnancy: A serious condition where the embryo attaches and develops inside the fallopian tube, requiring urgent medical attention
• Miscarriage: A pregnancy that ends before the 20th week, often caused by genetic abnormalities, infections, or diseases
• Preeclampsia: High blood pressure during pregnancy, which can develop into eclampsia, a life-threatening condition
• Gestational Diabetes Mellitus: A condition where the body cannot produce enough insulin during pregnancy, usually caused by hormone levels and weight gain
• Premature Birth: The birth of a baby more than 3 weeks before the estimated due date, which can lead to health complications
• Stillbirth: The death of a baby after the 20th week of pregnancy, but before birth

Healthy Behaviors During Pregnancy

• Eating well and gaining 25-35 pounds promotes personal and fetal health
• Regular physical activity, such as walking and swimming, helps maintain circulation and blood sugar levels
• Avoiding certain substances, such as alcohol, nicotine, and drugs, is crucial for fetal health and development

Childbirth

• Labor pushes the baby out of the pregnant person's body and into the world
• There are three stages of labor:
  1. First Stage: Contractions cause the cervix to thin and stretch, opening the cervix for the baby to pass through
  2. Second Stage: Uterine and abdominal muscles push the baby into the vagina and out of the body
  3. Third Stage: The placenta is delivered
• The Apgar test is used to evaluate the baby's health, responsiveness, and vital signs immediately after birth

Prenatal Care

• Regular visits to an obstetrician/gynecologist (OB/GYN) are essential for the developing baby and pregnant person's health
• Prenatal care involves monitoring the pregnancy, estimating the due date, and performing lab tests and physical exams
• Doctors may prescribe vitamins, such as folic acid, to support fetal development

Stages of Pregnancy

• First Trimester: Week 1-12
• Second Trimester: Week 13-26
• Third Trimester: Week 27 to the end of pregnancy