Obstetrics: Physiology

A pregnant woman complains of increased urination, and has +2 glucose on urine dipstick.

Pregnant women are more likely to get diabetes because human placental lactogen (hPL) reduces the response to insulin, to allow for a more constant supply of glucose to the fetus. However, finding glucose on urine dipstick can be normal, because during pregnancy there is increased blood flow to the kidneys and increased glomerular filtration rate (GFR). More filtration (high GFR) results in more glucose in the urine. Increased renal blood flow, results in increased urine output and along with compression of the bladder by the growing uterus, this often leads to increased urination.

A pregnant woman has elevated total T4 on routine labs but no symptoms of hyperthyroidism

Increased steroid binding globulin (SBG) leads to increased total T4 during pregnancy. TSH should be used for screening instead of total T4. If total T4 is high, free T4 can also be checked and should be normal.

Pregnant woman with nausea and vomiting.

Normal in pregnancy and occurs due to high progesterone (lowers the LES [lower esophageal sphincter] tone) and delays gastric emptying. High beta-hCG levels correlate with nausea symptoms, and since high beta-hCG is associated with lower risk of miscarriage, nausea is too.

Pregnant woman with dyspnea.

Dyspnea is normal and occurs due to decreased lung volumes [total lung capacity (TLC), functional residual capacity (FRC) and residual volume (RV)] by the 3rd trimester uterus.

Pregnant woman with backpain.

Backpain is common and occurs due to increased progesterone causing relaxation/ loosening of the joints and ligaments and also the gravid uterus causing lordosis during the 3rd trimester.

Pregnant woman with fatigue.

Fatigue often occurs due to dilutional anemia which occurs during pregnancy due to the increased plasma volume and increased iron use by the fetus. Prenatal vitamins or specific vitamin supplementation is often needed.

Pregnant woman notices her base heart rate is higher than it was pre-pregnancy

Cardiac output and heart rate both increase during pregnancy to supply blood to the fetus. A pregnancy heart rate even 90-100 bpm can be normal.