Blueprints - 1 - Pregnancy And Prenatal Care Flashcards
How sensitive are OTC pregnancy tests?
Very! They will be positive around the time of the missed menstrual cycle.
When does a pregnant patient’s β-hCG peak, and how high does it get?
10 weeks gestational age
100,000 mIU/mL
Where does β-hCG come from?
It is produced by the placenta
Confirmation of a viable pregnancy - β-hCG
1,500 - 2,000 mIU/mL
Happens around 5 weeks
Confirmation of a viable pregnancy - Ultrasound
Presence of a gestational sac as early as 5 weeks via transvaginal ultrasound.
When do you see fetal heart motion?
As early as 6 weeks
OR
A β-hCG of 5,000 - 6,000 mIU/mL
When is it called an embryo?
From the time of fertilization until the pregnancy is 8 weeks along (10 weeks gestational age)
When is it called a fetus?
After 8 weeks of pregnancy, up until the time of birth.
When is it called an infant?
Until the first anniversary of the delivery.
Definition - First Trimester
Pregnancy up to 12 weeks
Up to 14 weeks gestational age
Definition - Second Trimester
From 12 - 14 to 24 - 28 weeks gestational age.
Definition - Third Trimester
From 24 - 28 weeks until delivery.
Definition - Previable
An infant delivered prior to 24 weeks.
Definition - Preterm
An infant delivered between 24 and 37 weeks.
Definition - Term
An infant delivered between 37 and 42 weeks.
Definition - Postterm
A pregnancy carried beyond 42 weeks.
Gravidity
The number of times a woman has been pregnant.
Parity
The number of pregnancies that led to a birth:
At or beyond 20 weeks GA
OR
Weighing more than 500g
Nulli-
Primi-
Multi-
Nulli - 0
Primi - 1
Multi - >1
Remember the difference between parity and gravidity, though. A patient who is on her first ever pregnancy is primigravid and nulliparous.
Grand Multip
A patient whose parity ≥ 5
Gestational Age
Number of weeks and days since the LMP.
Typically this is around 2 weeks greater than developmental age.
Developmental Age
Number of weeks and days since fertilization.
This is also known as conceptional age or embryonic age.
Typically this is around 2 weeks less than gestational age
Why is gestational age usually 2 weeks greater than developmental age?
Typically fertilization happens around 14 days after the LMP
Nagele Rule
Estimated Date of Confinement (EDC) = Estimated Date of Delivery (EDD) = LMP - 3 months + 7 days
Exact Dating
EDC = EDD = LMP + 280 days
OR
If date of ovulation known through Assisted Reproductive Technology (ART),
EDC = EDD = Date of ovulation + 266 days
Signs of pregnancy
Chadwick Sign (Bluish discoloration of vagina and cervix)
Goodell Sign (Softenjng and cyanosis of the cervix at or after 4 weeks)
Ladin Sign (Softening of the uterus after 6 weeks)
Breast swelling and tenderness
Development of linea nigra (umbilicus to pubis)
Telangiectasias
Palmar erythema
Symptoms of pregnancy
Amenorrhea
Nausea and vomiting
Breast pain
Quickening - Fetal movement
Chadwick Sign
Bluish discoloration of vagina and cervix
Indicates pregnancy
Goodell Sign
Softening and cyanosis of the cervix at or after 4 weeks.
Ladin Sign
Softening of the uterus after 6 weeks
How early can pregnancy signs and symptoms present?
A few days to a week after a missed period
Dating - How much should the ultrasound differ from LMP in each trimester?
First Trimester - Not more than 1 week
Second Trimester - Not more than 2 weeks
Third Trimester - Not more than 3 weeks
Dating - How accurate is crown-rump length in the first half of the first trimester?
3 to 5 days
Landmarks - Fetal Heart Auscultation
Nonelectronic Fetoscopy - 20 weeks
Doppler Ultrasound - 10 weeks
Landmarks - Quickening (Maternal awareness of fetal movement)
Between 16 and 20 weeks
As pregnancy progresses, what happens to the accuracy of ultrasound dating?
Decreases
Oligo-ovulatory
Patient ovulates beyond the usual 14th day of the cycle. 5 - 15% of women are oligo-ovulatory.
What is a pitfall you can succumb to when treating an oligo-ovulatory patient?
Overdiagnosing prolonged pregnancy (≥ 41 weeks gestation
OR
Overdiagnosing postterm pregnancy (≥ 42 weeks gestation)
How much is cardiac output increased in pregnancy?
30 - 50%
At which point in pregnancy does the cardiac output increase the most?
First trimester. Maximum is reached between 20 and 24 weeks gestation, where it remains until delivery.
Describe the means for increase in cardiac output during pregnancy
Stroke volume increases
Heart rate increases as stroke volume decreases.
By the end of the third trimester, stroke volume has decreased to near pre-pregnancy levels.
What happens to systemic vascular resistance during pregnancy?
Decreases, leading to a drop in arterial BP
Likely due to elevated progesterone, which relaxes sloth muscle.
By how much does blood pressure drop during pregnancy?
Systolic - 5 to 10 mmHg
Diastolic - 10 to 15 mmHg
This drop bottoms out at week 24. From that point, the blood pressure slowly creeps back up to pre-pregnancy levels. Should never exceed them, though.
What happens to tidal volume during pregnancy?
Increases 30 - 40%
What happens to total lung capacity during pregnancy?
Decreases 5% due to elevation of the diaphragm
What happens to the expiratory reserve volume during pregnancy?
Decreases by about 20% due to the increase in tidal volume
What happens to minute ventilation during pregnancy?
Increases 30 - 40% due to tidal volume increase.
This leads to an increase in PaO2 and a decrease in PaCO2.
What happens to PaCO2 in pregnancy?
Decreases to ~30 mmHg (~40 mmHg is normal)
Likely caused by increased progesterone levels (this either increases responsiveness of respiratory system to CO2 or it acts as a primary stimulant, itself)
Leads to increased CO2 gradient between mother and fetus
What dies the CO2 gradient between mother and fetus do?
Facilitates oxygen delivery and carbon dioxide removal to and from the fetus.
Dyspnea of pregnancy
Occurs in 60 - 70% of patients
Possibly secondary to decreased PaCO2, increased tidal volume, or decreased total lung capacity.
“Morning Sickness”
Nausea and vomiting occur in more than 70% of pregnancies and can happen at any point in the day.
Oft attributed to elevated estrogen, progesterone and hCG.
Also may be due to hypoglycemia (treat with frequent snacking)
When should nausea and vomiting in pregnancy typically resolve?
14 to 16 weeks gestation
Hyperemesis Gravidarium
Severe “morning sickness” associated with:
Weight loss (≥5% of pre-pregnancy weight) Ketosis
Pregnancy’s effects on stomach and esophagus
Gastric emptying time prolongs
Gastroesophageal sphincter tone decreases.
Leads to reflux
Possibly combines with decreased esophageal tone to cause ptyalism (hypersalivation/spitting)
Pregnancy’s effects on the intestines
Large bowel has decreased motility.
This increases water absorption.
Leads to constipation.
Pregnancy - Gross effect on kidneys
Kidneys increase in size and ureters dilate.
Increases rates of pyelonephritis.
Pregnancy’s effect on GFR
Increases by 50% early on and is maintained until delivery.
Pregnancy’s effect on BUN and Creatinine
Both decrease by 25%
Pregnancy’s effect on the Renin-Angiotensin system.
Increased activity
Increased aldosterone levels
Increased sodium resorption
Plasma levels of sodium do not increase, though, due to the simultaneous increase in GFR.
Pregnancy’s effect on plasma volume, RBC volume and hematocrit
Plasma volume increases by 50%
RBC volume increases by 20 - 30%
Hematocrit decreases (dilutional anemia)
Pregnancy’s effect on WBC count
Increases to anywhere from 6 million to 16 million.
Mean level ~10.5 million/mL
During labor, this level may reach 20 million/mL due to stress.
Pregnancy’s effect on platelets
Slightly decreased platelet count.
Probably secondary to increased plasma volume and increased peripheral destruction.
A platelet count below 100 million/mL over a short time during pregnancy
Not normal. Investigate NOW.
Coagulation status of pregnancy
Hypercoagulable state
Increased number of thromboembolic events
May be due to elevations in: Fibrinogen Factor VII Factor VIII Factor IX Factor X
May also be due to other elements in the Virchow triad (increased venous stasis and vessel endothelial damage)
Clotting/bleeding times do not change.
Pregnancy and estrogen
Hyperestrogenic
Increased estrogen primarily produced by the placenta
Ovaries contribute some, but less
Normal estrogen production in the ovaries
Ovarian theca cells produce estrogen precursors.
Precursors are transferred over to ovarian granulosa cells.
Estrogen production by the placenta
Plasma-borne precursors are produced by the maternal adrenal glands.
Placenta converts precursors to estrogen.
Low estrogen levels - Effect on fetus
Fetal death
Anencephaly
hCG - Structure
Two dissimilar subunits (alpha & beta)
α-hCG
Identical to the α subunits of:
Luteinizing Hormone (LH)
Follicle-Stimulating Hormone (FSH)
Thyroid Stimulating Hormone (TSH)
hCG levels in pregnancy
Double every 48 hours (early pregnancy)
Peaks at 10 - 12 weeks
Declines gradually
Reaches steady state after week 15
hCG is made by
The placenta
hCG’s function
To maintain the corpus luteum in early pregnancy
Corpus Luteum’s function
Produces progesterone (to maintain the endometrium)
Once the placenta begins to produce progesterone instead, the corpus luteum degrades into the corpus albicans
Progesterone level in pregnancy
Increases over the course of pregnancy
Causes smooth muscle relaxation (affects GI, cardiovascular and GU systems)
hPL - Production and Function
Human Placental Lactogen
Aka
Human Chorionic Somatomammotropin (hCS)
Produced by the placenta
Helps ensure constant nutrient supply to fetus
hPL - Mechanism
Insulin antagonist
(Diabetogenic effects)
Induces lipolysis
(Concomitant increase in circulating free fatty acids)
Insulin level in pregnancy
Increased due to hPL’s insulin antagonist effects. Body is trying to compensate.
Prolactin level in pregnancy
Markedly increased
Decreases after delivery
Later increases in response to suckling
Pregnancy’s effect on thyroid hormones
Ultimately, pregnancy is a euthyroid state. Slight changes explained below.
Estrogen stimulates Thyroid Binding Globulin, leading to:
TBG increases
Total T3 and T4 increase
Free T3 and T4 remain constant
hCG weakly stimulates the thyroid, since α-hCG resembles the α-subunit of TSH:
T3 and T4 slightly increase
TSH slightly decreases
Musculoskeletal changes in pregnancy
Center of gravity shifts.
Leads to postural changes and lower back strain, worsening particularly in the 3rd trimester.
Sometimes pregnancy is associated with self-limited bouts of carpal tunnel.
Dermatologic changes during pregnancy
Increased Estrogen:
Spider angiomata
Palmar erythema
Increased melanocyte-stimulating hormones and steroid hormones:
Hyperpigmentation of nipples
Hyperpigmentation of umbilicus
Hyperpigmentation of abdominal midline (linea nigra)
Hyperpigmentation of perineum
Hyperpigmentation of the face (melasma or chloasma)
When you’re pregnant, you’re eating for two, right?
No. You’re eating for 1.15.
Caloric requirement is increased by 300 kCal per day when pregnant, and 500 kCal per day when breastfeeding.
Average caloric requirements of a non-pregnant woman
2,000 to 2,500 kCal per day
Recommended weight gain during pregnancy
20 - 30 lbs
15 - 25 lbs (if overweight)
28 - 40 lbs (if underweight)
Do most women gain the recommended amount of weight during pregnancy?
No. Most gain more. This leads to:
Complications in pregnancy
Postpartum weight retention
Downstream obesity
Increased nutritional requirements in pregnancy (non-caloric)
Protein Iron Folate Calcium Other vitamins/minerals
Protein requirement in pregnancy
70 - 75g per day
Normally it is 60g
Calcium requirement in pregnancy
1.5 g per day
Why do many patients develop iron deficiency anemia in pregnancy?
Increased hematopoietic demands from both the mother and the fetus.
Folate requirement in pregnancy
0.8 mg per day
(Normal is 0.4 mg)
Important for preventing neural tube defects
What is recommended for a patient whose hematocrit falls during pregnancy?
Increase iron intake with oral supplements
Initial Prenatal Visit - Overview
History
Physical Exam
Diagnostic Evaluation
Initial Prenatal Visit - History
Include:
Present Pregnancy:
LMP
Symptoms during pregnancy
Obstetric History of Prior Pregnancies:
Date
Outcome - Spontaneous Abortion (SAB) Therapeutic Abortion (TAB) Ectopic Pregnancy Term Delivery
Mode of Delivery
Length of Time in Labor and Second Stage
Birth Weight
Complications
Complete Medical History
Complete Surgical History
Complete Family History
Complete Social History
Initial Prenatal Visit - Physical
Complete physical exam
Keep prior medical/surgical history in mind
Pelvic exam w/pap smear unless one was done in the past 6 months
Culture for gonorrhea and chlamydia
Bimanual exam - size of uterus should be consistent with Gestational Age from the LMP
Ultrasound for dating if the patient is unsure of LMP. Accurate dating is CRUCIAL.
Initial Prenatal Visit - Diagnostic Evaluation
CBC Hematocrit Blood Type Ab Screen/RPR/VDRL for syphillis Gonorrhea and Chlamydia Culture Rubella Ab Screen HBsAg Urinalysis Urine Culture VZV titers (if no history of chicken pox) PPD for TB in high risk patients Urine pregnancy test (if patient is unsure) Serum β-hCG (if bleeding or cramping) Toxoplasma Titers Offer HIV test Early screening for aneuploidy: NT (ultrasound) Serum markers
