Developmental Psychology - Conception, Pregnancy, Birth - Quick Guides | Psychology

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Study GuideDevelopmental Psychology–Conception, Pregnancy,Birth1. Prenatal CarePrenatal development is the process that begins at conception and continues until birth. This periodincludes many important stages, each with specific changes that help a fertilized egg grow into ahealthy baby. Let’s walk through these stages step by step in a clear and simple way.1.1 Conception: How Pregnancy BeginsOvulation and the EggAroundday 14 of a 28-day menstrual cycle, ovulation usually occurs. During ovulation:•One ovary releases anegg (ovum).•Fingerlikestructures calledfimbriaeguide the egg into a nearbyfallopian tube.•If the egg isnot fertilized, it dissolves within about48 hours.1.2 How Sperm Reach the EggAfter ejaculation:•Sperm can reach the fallopian tube closest to the ovary in about90 minutes.

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Study Guide•Sperm move using a whipping motion calledflagellation, powered by energy-producingstructures calledmitochondria.•Out of about300 million sperm, only around2,000reach the correct fallopian tube.•Only about50 spermget close to the egg.•One spermsuccessfully penetrates and fertilizes the egg.Other sperm help by releasing an enzyme calledhyaluronidase, which softens the egg’s protectivelayer, thezona pellucida. Once one sperm enters, the egg’s membrane thickens to block all others.1.3 Fertilization and ChromosomesFertilizationis complete when the nucleus of the sperm fuses with the nucleus of the egg. At thismoment:•Thesex of the baby is determined.•Chromosomes carry genes, which are the body’s biological instructions.•The egg always provides anX chromosome.•The sperm provides either anX or a Y chromosome.This means:•XX = female•XY = maleThe X chromosome carries essential genetic information, while the Y chromosome mainly triggersmale development.1.4 Multiple PregnanciesAmultiple pregnancycan happen in two ways:•Identical twins or tripletsform when one fertilized egg splits into two or more embryos.•Fraternal twinsform when two separate eggs are fertilized by two different sperm.

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Study Guide1.5 Early Cell DivisionWithin24–36 hours, the fertilized egg (now called azygote) begins dividing rapidly:•1 cell becomes 2•2 become 4•4 become 8, and so onAll of this happens as the zygote travels down the fallopian tube toward the uterus.1.6 Implantation: Attaching to the UterusAboutone week after conception, the zygote becomes ablastocyst, a hollow ball of about100cells.•The blastocyst floats in the uterus for about3 days.•It then attaches to theendometrium, the inner lining of the uterus.•Outer cells calledtrophoblastsrelease enzymes that help the blastocyst embed itselfsecurely.This process is calledimplantation.1.7 From Zygote to Embryo to Fetus•After implantation and for the first8 weeks, the developing organism is called anembryo.•From the end of week 8 until birth, it is called afetus.During implantation:•Cell division speeds up.•Early organs and tissues begin to form.•A groove called theneural grooveappears and later develops into the brain and nervoussystem.•The trophoblasts help form theplacenta, umbilical cord, and amniotic sac.

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Study Guide1.8 The First Trimester (Weeks 1–12)The Placenta and HormonesTheplacentais a disk-shaped organ that:•Connects to the fetus through theumbilical cord•Supplies oxygen, nutrients, and antibodies•Removes waste from the fetusEarly in pregnancy, the placenta releaseshuman chorionic gonadotropin (HCG).•HCG prevents menstruation by maintaining thecorpus luteum.•Pregnancy tests detect HCG in blood or urine.•Home pregnancy testsmay give false negatives, makinglaboratory tests more reliable.1.9 Umbilical Cord and Blood ExchangeByweek 5, theumbilical cordforms.•It containsone vein and two arteries.•Blood exchange happens throughchorionic villi, tiny projections in the placenta.•The mother’s and fetus’s bloodnever mix, but substances like oxygen, nutrients, viruses, anddrugs can pass between them.1.10 Hormones and Physical ChangesAfter the first trimester, the placenta produces:•Progesterone and estrogen, which:oEnlarge reproductive organsoRelax ligamentsoDevelop the uterine lining and breastsoPrevent uterine contractions•Placental lactogen, which prepares the breasts for milk production

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Study Guide1.11 Amniotic Sac and FluidThe embryo is surrounded by:•Theamnion(inner membrane)•Thechorion(outer membrane)Together, they form theamniotic sac, filled withamniotic fluid.This fluid:•Cushions the fetus•Protects against shock•Maintains a constant temperature1.12 Confirming PregnancyPregnancy can be confirmed by:•AnHCG-based test•Ballottement, where a doctor feels for the fetus during a pelvic exam•Hearing theuterine souffle, a rushing sound made by blood flow, using a stethoscope1.13 Growth and Development in the First TrimesterDevelopment follows acephalocaudal pattern, meaning growth starts at the head and movesdownward. This is why the fetus’s head is much larger than the rest of its body early on.Three cell layers form:•Ectoderm→ skin, nervous system, sensory organs•Mesoderm→ muscles, bones, circulatory and reproductive systems•Endoderm→ digestive, respiratory, and glandular systems

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Study GuideBy:•Week 7: Digestive and respiratory systems begin limited function•Week 8: Embryo is about 1¼ inches long and weighs 1/30 of an ounce•Week 10: Arms, legs, hands, feet, and toes are visible•Week 12: Fetus looks human, weighs about 1 ounce, is 3–4 inches long, and has visible sexorgans1.14 The Second Trimester (Weeks 13–26)•Begins atweek 13•Byweek 14, the mother can feel fetal movement•Byweeks 17–18, doctors can hear the heartbeat•Betweenweeks 20–26, the fetus may weigh up to2 pounds•The fetus can open its eyes, sleep, wake, and move its limbs1.15 The Third Trimester (Week 27 to Birth)•Begins aroundweek 27•The fetus develops alayer of fat, giving it a baby-like appearance•The fetus usually turnshead-downin preparation for birth•If it does not, abreech presentationoccurs (feet-first or hips-first)By:•Month 8: The fetus weighs about5 pounds•After that, it gains about½ pound per week•Skin becomes less red and smoother•Awaxy coatingcovers the skin to protect it during delivery

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