OB Prenatal Development and Pregnancy Changes

What is conception?

• Encompasses the entire journey from fertilization to implantation

What is the first part of conception?

• Fertilization occurs and the sperm enters ovum (egg)

• Membrane now unaccesable

• Pairing of chromosomes (46)

Where does Fertilization occur?

• Outer 3rd of fallopian tube

What is the implantation stage of conception?

• 6-10 days following conception

• May cause “implantation bleeding” at time of first missed period

• Blastocyst burrows into the endometrium

What is a blastocyst?

• Structure of evolving embryo

Implantation Bleeding vs. Period

Implantation Bleeding

• Nausea, light cramps, frequent urination

• Few drops of blood

• Duration: 1-2 days

• Color: light pink and brown

Period

• Heavier cramps, PMS, breakouts

• flow of blood

• Duration: 4-7 days

• Color: bright red

What are the stages of intrauterine development?

• Ovum/Zygote

• Embryo

• Fetus

What is the Ovum/Zygote stage of intrauterine development?

• 1st 14 days

• Not susceptible to teratogens

What is the embryo stage of intrauterine development?

• Day 15 through week 8

• CRITICAL TIME IN ORGAN DEVELOPMENT

• VULNERABLE TO TERATOGENS

What is the fetus stage of intrauterine development?

• Week 9 through END OF PREGNANCY

• Less sensitive to teratogens

What are the 3 different trimesters of pregnancy?

• 1st = through the end of the 13th week

• 2nd = 14 weeks through end of the 27th week

• 3rd = 28 weeks through end of 40 weeks

What are the two different ways twins can form?

• Dizygotic fertilization: 2 separate eggs, 2 separate sperm

• Monozygotic fertilization: 1 egg, 1 sperm, cell division (one egg splits into two embryos)

What are the different types of twins?

• Di/Di: 2 chorions, 2 amniotic sacs

• Mono/Di: 1 chorion, 2 amniotic sacs

• Mono/Mono: 1 chorion, 1 amniotic sac (very high risk, can get tangled)

What is present with a 24 day old embryo?

• 2 chamber heart beating for 2 days already

What happens at 6 weeks?

• the yolk sac is clearly visible on an ultrasound

What occurs at 8 weeks?

• all organ systems and external structures are present

• ~3cm long

What happens at 12 weeks?

• 12 weeks: sex identifiable

What happens between 14-20 weeks?

• “Quickening”- first fetal movement felt

• 1st time moms may not feel this until later when movement is bigger and more pronounced

What happens at 20 weeks?

• initial respiratory- like movements

• Vernix: White cheesy stuff that protects skin

• Lanugo: fine hair, holds vernix on, helps regulates temp.

What happens at 24 weeks?

• Alveolar ducts and sacs present

• Baby can hear

• Age of “viability”

What happens at 28 weeks?

• Eyes open

• Suck reflex begins

What happens at 30+ weeks?

• Subcutaneous fat development

• Continued CNS/brain development

• Continued lung development

Placenta acts as the…..

• LUNGS & LIVER

How does fetal circulation work?

• Baby’s do not breathe while inside the mother, their lungs are not involved in gas exchange

• Delivery of oxygen and nutrients are from the placenta

• Waste products eliminated by mother’s body

• Three fetal shunts that deal with blood flow

What is the purpose/role of the 3 fetal shunts?

• Redirect blood flow away from the nonfunctional fetal lungs

• Ensure highest oxygenated blood reaches the heart and brain

What are the 3 specific fetal shunts involved in fetal circulation?

• Ductus Venosus: carries oxygenated blood from the umbilical vein to inferior vena cava (bypasses liver)

• Foramen Ovale: allows blood to flow from right atrium to left atrium (bypasses lungs)

• Ductus Arteriosus: connects the pulmonary artery to aorta (bypasses lungs)

What is the role of the umbilical cord?

• transports oxygen, carbon dioxide, nutrients, and wastes from placenta to fetus

• Twisting and spiraling of cord due to fetal movement

• Average 1.4-2.3 feet long at term

How many arteries/veins does the umbilical cord have?

AVA

• 2 umbilical arteries

• 1 umbilical vein

What do the umbilical arteries do?

• Carry deoxygenated blood away from baby back to the placenta

What does the umbilical vein do?

• Carry oxygenated blood from placenta to fetus

What is Wharton’s jelly?

• Prevents compression of vessels

What is the function of amniotic fluid?

• acts as cushion to protect embryo from injury

• Thermoregulation & antibacterial properties

• Allows movement; helps musculoskeletal growth

• Assists in lung development

• Prevents umbilical cord compression

What does the amniotic fluid consist of in the different trimesters?

• 1st: mostly maternal blood plasma

• 2nd and 3rd: fetal lung fluid and urine

What is the average volume of amniotic fluid at term? What is too much and too little fluid?

• Average volume by term = 800mL

• Polyhydraminos (too much fluid) = > 2 liters

• Oligohydraminos (too little fluid) = < 300mls

What are the functions of the placenta?

• Provides metabolic and nutrient exchange between embryo/fetus and maternal circulation

• Acts as LUNGS and LIVER

• Fetal waste is excreted through diffusion

• Endocrine functions: produces hormones (progesterone and estrogen) essential to fetal survival

How does the placenta develop?

• Develops at site of implantation

• Structure is completed by week 12

• Widens until 20th week gestation

• Thickens in size from 20th to 40th week gestation

What are the different sides of the placenta?

• Chorion = maternal side

• Amnion = fetal side

What happens to the uterus during pregnancy?

• Estrogen and Progesterone stimulates uterine growth

What happens to the cervix during pregnancy?

• Cervix is firm/closed to maintain pregnancy

  • Mucus plug early on

• Changes to soft/elastic tissue so that it can dilate fully during labor/birth

• Goodell’s sign: ~6 weeks = increase in cervical vascularity = softening of the cervix

What happens to the vagina during pregnancy?

• Thickening of the vaginal mucosa

• Chadwick sign: bluish coloration of vagina/cervix d/t increased vascularity

• Increase in vaginal secretions

  • Secretions are white/greyish

What happens to the breasts during pregnancy?

• Enlargement

• Prominent superficial veins

• Darkening of areola

• Striae (stretch marks)

• Colostrum production 2nd trimester on (after 15 weeks)

What happens to the cardiovascular system during pregnancy?

• Increase in blood volume - 40-50% (1200-1600ml) by 32 weeks

• Increase in heart rate (10-20bpm over baseline), therefore increased cardiac output

• Decrease in blood pressure (slightly in 2nd trimester and returns to pre-pregnancy levels by term)

What does the enlarged uterus cause?

• Stasis of blood flow in lower extremities

• Dependent edema, varicosities, vena cava syndrome, postural hypotension

What happens to labs during pregnancy?

• Increase in RBC volume (20-30%) = increase in iron needs

• Increase in plasma volume (increases more than RBCs = decrease in H&H values)

  • Hemodilution = Physiologic Anemia of pregnancy

  • Lower H&H levels are normal

• Increase in WBC levels (leukocytosis)- mostly 3rd trimester

• Hypercoagulable state!!

What happens to the respiratory system during pregnancy?

• Increase in oxygen requirements/consumption → Increase in RR

• Breathing changes from abdominal to chest

• Epistaxis and nasal stuffiness r/t hormone-induced edema/hyperemia

• Chest cavity expands (increased AP diameter)

What happens to the GI system during pregnancy?

• N/V: unknown etiology, most common in 1st trimester

• Bleeding gums

• Susceptible to gingivitis

• Increase in salivation (ptyalism)

• Delayed gastric emptying = bloating, heartburn, constipation, hemorrhoids, and gallstones

What happens to the GU system during pregnancy?

• 1st and 3rd trimesters: urine frequency increases

• GFR increases 50% during pregnancy

• Elongation of ureters (especially right) causes stasis of urine = increase in UTI’s

What happens with fluid and electrolytes during pregnancy?

• Increase of total body water of 6.51 to 8.51

• Women can become dehydrated quickly and severely

• Susceptible to pylonephritis and hydronephrosis

What skin and hair changes occur during pregnancy?

• Pigmentation changes (hormones)

  • Areola (darker)

  • Lines nigra- dark vertical line on stomach

  • Chloasma/Melasma- mask of pregnancy, hyperpigmentation on face

• Striae gravidarum

• Increase in hair growth during pregnancy

• Increase in hair loss after pregnancy

What musculoskeletal changes occur during pregnancy?

• Postural changes

  • Lordosis- back arching

  • Low back ache

• Shift in center of gravity

• Relaxation of pelvic joints

• Diastasis recti abdominis: separation of abdominal muscles

What foods should you avoid during pregnancy?

• Overall avoid things with infection and teratogen risk

• Avoid eating fish with high levels of mercury: swordfish, shark, king mackerel

• Avoid foods known to cause food borne illnesses: sushi, soft cheeses, deli meats

What should you make sure you get plenty of (nutrition wise) during pregnancy?

• Get plenty of Folate (folic acid is synthetic folate):

  • 400mcg pre-pregnancy and 600mcg during pregnancy

• May need additional iron due to the increase in RBC production

How much weight should you gain during pregnancy?

• 25-35 lbs with normal pre-pregnancy weight (more with multiples)

• 15-25 lbs if overweight/obese

What are some psychological and cultural changes during pregnancy?

• Mother may feel wide range of emotions

• Partners face adjustments as they accept new role

• Siblings require assistance dealing with birth of new baby

• INDIVIDUALIZING CARE FOR ALL PT’s IS IMPORTANT

  • Don’t assume

  • Perform thorough cultural/family assessment

  • Ask about birth plan