Maternal Physiology Flashcards
Major hormones involved in regulating lactation
- Prolactin: Stimulates production of milk
- Progesterone: Interferes with prolactin signaling in breat alveolar cells, suppressing milk production
- Oxytocin: Stimulates lactation
Clinical “types” of gestational diabetes
A1: Diet controlled
A2: Requiring pharmacologic intervention
What abnormalities are infants born to patients with gestational diabetes at increased risk for?
Metabolic features of GDM that predispose to poor outcomes
Pregnancy is a ___-genic state
Pregnancy is a diabeto-genic state
As part of normal pregnancy physiology, fasting insulin levels increase and post-prandial blood glucose increases, while hepatic insulin sensitivity decreases.
Decreased insulin sensitivity is mediated by human placental lactogen, which is a strong anti-insulin hormone. Increased baseline insulin is mediated by estrogen and progesterone, which induce pancreatic beta islet cell hypertrophy.
Why does peripheral sensitivity to maternal insulin decrease in pregnancy?
Human placental lactogen from the placenta antagonizes its activity in these tissues
Screening for gestational diabetes
- If risk factors present, screen at first OB visit with 50g glucose tolerance test (1 hour, threshold >200 mg/dL)
- If no risk factors present, screen at 26-28 wks gestation with 50g glucose tolerance test (1 hour, threshold >140), and if this is positive, a confirmatory 100g glucose tolerance test (3 hours, threshold >140).
Treating GDM
- Behavioral:
- Diet
- Pharmacologic:
- 1st line: Insulin
- 2nd line: Metformin, glyburide with monitoring
Fetal complications of GDM
- Shoulder dystocia due to accumulation of fetal fat at shoulders
- Increased need for caesarean delivery
-
polyhydramnios (think of it as fetal polyuria)
- Increases risk for pre-term labor
Pre-term labor in GDM
- Traditionally, for pre-term labor we administer betamethasone in order to ensure sufficient surfactant production
- But. . . in patients with GDM this has the side effect of causing a glucose surge
- This necessitates close monitoring and potentially insulin therapy
- Effects can be seen up to 2 weeks following betamethasone administration
Neonatal metabolic consequences of GDM
- When the infant is born, it will have been accustomed to dealing with high levels of glucose by producing an excess of insulin
- When this supply is cut off, the infant will still be producing that insulin excess for ~24 hours, which may lead to:
- Neonatal hypoglycemia
- Hypercalcemia
- Hyperbilirubinemia
- Polycythemia
- Later on, they also are at increased risk for childhood obesity and adult type II diabetes
Maternal risks of GDM
-
Amenable to glucose control:
- All of the normal DM stuff
- Increased risk of need for caesarean delivery
- Risk of severe perineal laceration
-
Not amenable to glucose control:
- Pre-eclampsia
- Development of overt type II diabetes
Progesterone and blood pressure
Progesterone both promotes vasuclation of the placenta and relaxes vascular smooth muscle, leading to decreased blood pressure.
This reaches a nadir around the end of the 2nd trimester.
Six key hormones of pregnancy
Pregnancy wheel
Pathology that can be induced by elevated progesterone in pregnancy
- GERD (smooth muscle relaxation)
- Gallstones (inhibition of CCK)
- Constipation (decreased GI motility)
- N/V (along with beta hCG, morning sickness)
Hyperemesis gravidarum
- When the nausea and vomiting of pregnancy becomes truly pathologic
- Weight loss
- Ketonemia
- Metabolic alkalosis (similar physiology to bulemic metabolic alkalosis)
Three contributors to GERD during pregnancy
- Progesterone (decreased motility, smooth muscle relaxation)
- Relaxin (smooth muscle relaxation)
- Mass effect of enlarged uterus (pushes stomach up)
Rate of increased cardiac output in pregnancy
Slightly outpaces the rate of volume expansion in order to also cover the decreasing vascular resistance
Increases by about 25% by 8 weeks, 50% by the third trimester
In the first half of pregnancy, CO increases due to ___.
In the second half of pregnancy, CO increases due to ___.
In the first half of pregnancy, CO increases due to increased stroke volume.
In the second half of pregnancy, CO increases due to increased heart rate.
Supine postural hypotension syndrome
- The hypotension that pregnant women experience when lying flat on their backs
- Due to compression of the IVC by the womb
-
We advise pregnant women to not lay flat on their back while they are sleeping
- We recommend sleeping with a left tilt (IVC is on the right) or on their side
Respiratory changes during pregnancy
- Oxygen demand increases by 20%
- Minute ventilation increases by 30-40%
- Consequently, in order to meet this demand for oxygen, women must hyperventilate and blow of extra CO2
- This is the mechanism by which the physiologic alkalosis of pregnancy occurs
- It is balanced by kidney bicarbonate excretion
Lab features of the physiologic alkalosis of pregnancy
A fully compensated respiratory alkalosis with normal pH
Changes in the maternal thorax during pregnancy
- Diaphragm elevated by 4cm due to mass effect
- Chest diameter and circumference increase
Physiologic anemia of pregnancy
- Plasma volume increases by 45% by the third trimester
- RBC volume increases by 35% by the third trimester
- You do the math
- This makes the average Hb about 12.5 in the pregnant woman at term, compared to 14 in the non-pregnant woman
- Iron supplementation is given to help prevent further anemia
Maternal blood pressure starts to decline by week ___.
They reach a nadir and begin to rebound by around ___.
Maternal blood pressure starts to decline by week 7.
They reach a nadir and begin to rebound by around week 24-26.
Common cardiovascular exam findings in pregnancy
- Distended neck veins common due to physiologic increase in volume
- Systolic flow murmur common due to physiologic increase in CO and anemia
Maternal fetal circulation
- Three shunts of pregnancy (in order from umbilical vein):
- Ductus venosus
- Foramen ovale
- Ductus arteriosus
1000 foot view of pre-eclampsia and eclampsia
Four types of hypertension in pregnancy
- Chronic hypertension (Predates pregnancy or diagnosed pre-20 wk mark)
- Gestational hypertension (New onset post-20 wk mark, WITHOUT proteinuria OR end organ dysfunction)
- Pre-eclampsia (New onset post-20 wk mark, WITH proteinuria OR end organ dysfunction)
- Chronic hypertension with superimposed pre-eclampsia (Pre-existing chronic hypertension with NEW proteinuria OR end organ dysfunction starting post-20 wk mark)
Cytotrophoblast invasion of uterine spiral arteries
- A normal step in placental development
- Cytotrophoblasts enter uterine arteries and replace their endothelium through metaplasia
- Allow for conversion of high-resistance, small-diameter vessels to high-capacitance, low-resistance vessels
- This process is disordered in pregnant women who will eventually develop pre-eclampsia, such that the maternal endothelium is not replaced by cytrotrophoblasts.
Risk factors for pre-eclampsia
- History of pre-eclampsia
- Primiparity
- Pre-eclampsia in first degree relative
- Multiple gestation
- Maternal factors:
- HTN, kidney disease, diabetes, hypercoagulability, SLE, obesity, >40 years age
Diagnosing pre-eclampsia
Past what point are we no longer worried about pre-eclampsia for a given pregnancy?
37 wks gestational age