Prenatal Influences on Healthy Development

Flashcards reviewing key concepts of prenatal genetics, fertilization, fetal development stages, critical periods, microbiomes, teratogens, and clinical care from NURS 300 Chapter 6.

What multigenerational health impact can maternal pregnancy practices have according to Leifer (2022)?

Healthcare practices, missing nutrients, stress, or toxin exposures during pregnancy can influence the health of the child, grandchild, and great-grandchild, setting adult-onset diseases in motion.

What is a human genome?

The complete set of DNA contained in all of a cell's nucleus, representing the full instruction manual of approximately 30,000 genes.

How many chromosomes do human cells normally contain?

Humans normally have 46 chromosomes, arranged in 23 pairs.

What is the distinction between a gene and an allele?

A gene is a single unit of the genetic code, whereas an allele is the pair of genes (one inherited from each parent) for a specific trait.

What mechanism is used in gene therapy to deliver replacement genes into cells?

Gene therapy uses a virus or bacterial vector to carry a healthy gene into a target cell to replace a missing or defective one.

What were the five original goals of the Human Genome Project (1990–2001)?

1. Identify the 30,000+ genes in human DNA; 2. Sequence the billions of DNA chemicals; 3. Build tools to analyze findings; 4. Address ethical, legal, and social implications (ELSI); 5. Transfer technology to the private sector.

What proportion of offspring will express the dominant trait when both parents are carriers ($Dr$) for a recessive trait?

Approximately 3 out of 4 offspring (75%) show the dominant trait, while 1 out of 4 (25%) shows the affected recessive trait ($rr$).

What three engineered gene tools are utilized in genetic therapy?

Therapeutic genes (to repair DNA), suicide genes (to destroy defective genes), and pure genes (to replace a missing gene).

Which condition has been the primary focus of most gene therapy applications according to Lundstrom (2019)?

Cancer.

What condition does the Guthrie test screen for in newborns?

Phenylketonuria (PKU), where untreated phenylalanine accumulates and causes cognitive damage.

What does hemoglobin electrophoresis detect in clinical screening?

Types of anemia, including sickle cell trait and sickle cell disease.

What do presymptomatic DNA tests for conditions like Huntington's disease or ALS detect, and what non-medical concerns accompany them?

They detect adult-onset disease risk before symptoms appear. Non-medical concerns include psychological burden and potential impacts on employment or life-insurance eligibility.

What does the ELSI program stand for in genomics research?

Ethical, Legal, and Social Implications.

What are the survival lifespans of sperm and ovum relative to fertilization?

Sperm lives up to 5 days in the reproductive tract, while the ovum lives for only 24 hours after ovulation.

Where in the female reproductive tract does fertilization normally take place?

In the upper fallopian tube.

Why does the father determine the biological sex of the fetus?

The ovum always contributes an X chromosome, whereas sperm can carry either an X or a Y chromosome ($XX$ = female, $XY$ = male).

How can maternal physiology influence sex determination during fertilization?

Estrogen levels and the pH of the reproductive tract affect which X- or Y-bearing sperm survive and how fast they travel (Ross & Ervin, 2016).

What is the chronological sequence of prenatal stages from fertilization to birth?

Zygote $\rightarrow$ Implantation $\rightarrow$ Embryo (from ~2 weeks) $\rightarrow$ Fetus (from 9th week to birth) $\rightarrow$ Viable (by ~20–24 weeks).

What is an ectopic pregnancy, and why is it considered a medical emergency?

An ectopic pregnancy occurs when the zygote implants outside the uterus (most commonly in the fallopian tube), which can rupture the tube and cause life-threatening internal bleeding.

In which week of embryonic development does the neural tube form and the heart begin to beat?

Week 3.

At what gestational age does the embryo acquire a distinct human appearance and transition into the fetal period?

Week 8.

At what point in gestation is a fetus considered viable outside the uterus?

By approximately 20–24 weeks, though NICU support is required due to immature lung function.

Why is folic acid supplementation essential during the earliest weeks of pregnancy?

The neural tube closes in Week 3, often before a woman knows she is pregnant; folic acid deficiency at this time can cause neural tube defects such as spina bifida.

What food sources are rich in folate?

Beans, soy, lentils, peas, and leafy green vegetables such as spinach.

Do maternal and fetal blood supplies mix during normal pregnancy?

No, maternal and fetal blood do not normally mix; placenta-mediated circulation exchange begins at the end of month 3.

How do monozygotic and dizygotic twin pregnancies differ genetically and structurally?

Monozygotic (identical) twins develop from one fertilized ovum splitting into two embryos (same sex, genetically identical). Dizygotic (fraternal) twins develop from two separate ova fertilized by two separate sperm (same or different sex, genetically as alike as regular siblings).

Why do twin pregnancies present a higher risk for prematurity?

The uterus becomes overdistended, or the placenta cannot supply sufficient nourishment to support both fetuses to full term.

How does a newborn acquire its initial microbiome?

In utero (influenced by maternal diet, stress, illness, and medications), during birth while passing through the birth canal, and in the first hours via skin contact and breastfeeding.

What is dysbiosis, and what conditions are linked to early-life versus later-life microbial shifts?

Dysbiosis is a harmful shift in the body's microbial community. Early-life dysbiosis has been linked to autism, while later-life dysbiosis is linked to dementia (Wu et al., 2019).

What are the fetal consequences of maternal alcohol intake during pregnancy?

Fetal alcohol syndrome, causing cognitive impairment and abnormal facial features; there is no safe amount of alcohol during pregnancy.

What is the primary fetal effect associated with cigarette smoking during pregnancy?

Decreased birth weight.

Why must pregnant women avoid changing cat litter?

Cat litter poses a risk of toxoplasmosis, an infection that causes devastating outcomes in newborns.

What substance in excess licorice harms fetal development, and what long-term effects does it have?

Glycyrrhizin causes excess fetal cortisol, which is linked to deficits in cognition, memory, and aggression control in adult life.

What are the general guidelines for exercise frequency and caloric intake during pregnancy?

Exercise 30 minutes per day, 5 days per week (e.g., walking, swimming, prenatal yoga) and increase dietary intake by ~300 calories per day to support an expected weight gain of 25–30 lb.

What warning signs require immediate cessation of exercise during pregnancy?

Vaginal bleeding or discharge, uterine contractions, or decreased fetal movement.