Preganancy

• Conception is the union of a sperm cell and an ovum, forming a zygote
• Each ejaculate contains an average of 200 to 400 million sperm
• Fertilization normally occurs in a fallopian tube
• Ovum is surrounded by zona pellucida, which must be penetrated by sperm for fertilization
• Sperm secrete the enzyme hyaluronidase, which briefly thins zona pellucida, enabling penetration
• Ova carry X sex chromosomes, while sperm carry either X or Y sex chromosomes
• Girls are produced from the union of 2 X chromosomes, while boys are produced from an X and a Y chromosome
• Y sperm appear to be faster swimmers
• Male fetuses are more likely lost in spontaneous abortion, which helps balance the sexes
• Ovum can be fertilized for 4-20 hours after ovulation
• Sperm are most active within 48 hours after ejaculation
• Ways to predict ovulation include basal body temperature (BBT) chart, analyzing urine or saliva for luteinizing hormone, and tracking vaginal mucus
• Implantation is the attachment of the fertilized egg to the uterus, happening within 3 to 5 days of fertilization
• The outer layer of cells during implantation gives rise to the placenta and other supporting tissues needed for fetal development
• The embryonic stage lasts from implantation through the eighth week, where differentiation of major organ systems occurs
• The amniotic sac suspends and protects the fetus during prenatal development
• The placenta serves as a relay station between mother and embryo, allowing the exchange of nutrients and wastes
• The fetal stage begins by the ninth week and continues until birth
• During the third trimester of pregnancy, the fetus gains most of its weight and is able to grasp objects as well as open and close its eyes
• Rubella and syphilis are complications during prenatal development that can cause mental retardation, heart disease, or miscarriage
• HIV/AIDS destroys white blood cells in the immune system
• Toxemia is a life-threatening condition characterized by high blood pressure during pregnancy
• Rh incompatibility can cause brain damage or death in the fetus
• Drugs taken by the mother during pregnancy, such as Diethylstilbestrol (DES), can have harmful effects on the child