BIOL 80A Final | Pregnancy and Fetal Development by Trimester

What common maternal symptoms occur in the first trimester?

Fatigue, morning sickness, breast tenderness, cravings/aversions, GI issues (heartburn/constipation), mood swings, headaches, slight weight gain.

What major maternal physiological changes occur in the first trimester?

Increased blood volume and cardiac output; ~2–5 lbs gained.

What key fetal developments occur in the first trimester?

Organs begin forming; heartbeat detectable (6–7 wks); fetus by 8 weeks; movement by 12 wks; systems functioning; ~5 cm in length.

Why is the first trimester the most vulnerable to teratogens?

All organs/structures are forming—disruption leads to severe defects or miscarriage

what are some examples of harmful substances in the first trimester?

Alcohol, smoking, isotretinoin, thalidomide, amphetamines, X-rays, lead, heavy aspirin use, toxoplasmosis sources.

what are common maternal changes in the second trimester?

 Symptoms ease; melanin increases (darker areolas, linea nigra); relaxin causes aches; baby bump grows; weight gain increases; quickening (~20 wks).

What major hormonal shift occurs in the second trimester?

Placenta takes over estrogen/progesterone production

what are some key fetal developments in the second trimester?

Organs continue developing; sex visible on ultrasound; active movement; hearing develops; lungs formed but not functional; ~12 in & ~2 lbs.

When is fetal survival outside the uterus first possible?

Around 24–26 weeks.

what are some common maternal experiences in the third trimester?

 Increased discomfort, shortness of breath, back pain, frequent urination, swelling, cramps, hemorrhoids, Braxton-Hicks, colostrum, rapid weight gain, fetal “dropping.”

what are some key fetal developments in the third trimester?

Rapid growth; fat accumulation; lung/brain maturation; bone hardening; head-down positioning; ready for birth in final month; ~6–9 lbs.

What does hCG do?

Maintains the corpus luteum in the first trimester

What are major functions of estrogen in pregnancy?

Uterine/mammary growth, fetal tissue growth, lung/liver maturation, regulates progesterone

What are major functions of progesterone in pregnancy?

Maintains endometrium, supports fetal organ maturation, inhibits uterine contractions

What does relaxin do?

Loosens pelvic ligaments/joints and helps cervix dilate.

What contributes to pregnancy weight gain?

Fetus, placenta, amniotic fluid, breast tissue, blood volume, fat stores, and enlarged uterus.

 What is the typical total pregnancy weight gain?

 About 22–36 lbs (10–16.3 kg)