Pregnancy Flashcards
Question
C Human placental lactogen
During pregnancy, a physiologic increase in maternal insulin resistance occurs during the second and third trimesters, largely due to human placental lactogen (hPL), a peptide hormone secreted by the syncytiotrophoblast. hPL establishes a glucose-sparing effect that results in:
Increased maternal glucose levels: allows glucose to freely cross the placenta for consumption by the fetus for energy
Increased maternal proteolysis: provides a readily available supply of amino acids for the fetus
Increased maternal lipolysis: leads to increased free fatty acids and ketones to provide energy to the mother, preserving glucose and amino acids for the fetus
hPL also stimulates maternal pancreatic beta-cell proliferation to increase insulin production to counteract the rising resistance. This physiologic process becomes pathologic (ie, gestational diabetes mellitus) when the pancreatic function is not sufficient to overcome the pregnancy-related increase in insulin resistance.
Average levels of hPL rise with increasing gestational age, reflecting the increasing energy requirements of the growing fetus. Therefore, screening for gestational diabetes is performed in the late second or early third trimester (when plasma levels of hPL are peaking) to ensure screening accuracy.
(Choice A) Growth hormone, released from the pituitary gland, causes an increase in insulin resistance and fat breakdown; however, growth hormone secretion does not increase during pregnancy.
(Choice B) In early pregnancy, the placental syncytiotrophoblast secretes human chorionic gonadotropin, a peptide hormone, which stimulates the corpus luteum to produce progesterone, a steroid hormone. Progesterone is necessary to maintain the secretory endometrium, allowing the pregnancy to persist through term.
(Choice D) Prolactin is a peptide hormone secreted by lactotroph cells in the anterior pituitary. It stimulates ductal and alveolar growth in breast tissue and is responsible for milk production and lactation in postpartum women.
(Choice E) Pregnancy increases the levels of thyroid-binding globulin, leading to increased total circulating T3 and T4. However, free thyroid hormone levels remain essentially normal.
Educational objective:
Human placental lactogen creates a fetal glucose-sparing effect by increasing maternal insulin resistance during the second and third trimesters, leading to a rise in serum glucose that helps provide adequate nutrition to the growing fetus. Gestational diabetes occurs when the compensatory rise in maternal insulin secretion is inadequate to prevent serum glucose levels from reaching excessively high levels.
Connexin 43 upregulation and pregnancy
Communicating gap junctions are especially important during labor and delivery, which require coordination and synchronization of individual myometrial (uterine smooth muscle) cells.
Gap junctions facilitate electrical and chemical communication between neighboring cells via a connexon, a connecting cylinder with a central channel composed of connexin proteins (eg, connexin 43). In preparation for labor, increasing estrogen levels stimulate upregulation of connexin 43, increasing formation of gap junctions between individual myometrial cells. An increase in gap junction density allows the passage of small ions between neighboring myometrial cells, resulting in coordinated, synchronous labor contractions.
Estrogen also increases the expression of uterotonic oxytocin receptors, Gq–coupled membrane receptors that increase intracellular calcium levels, heightening myometrial excitability.
Question
B. Dilated, coiled endometrial glands and edematous stroma
This patient with vaginal bleeding, positive β-hCG, and no visible intrauterine gestational sac has a pregnancy of unknown location, which is concerning for an ectopic pregnancy (ie, embryo implantation in an extrauterine location such as the fallopian tube). Early ectopic pregnancy may not be visible on ultrasound; therefore, patients require serial β-hCG measurements for diagnosis.
This patient has an abnormally low β-hCG level for gestational age (eg, 800 IU/mL at 6 weeks gestation) plus an inappropriate rise in β-hCG level. In normal pregnancies, these levels double approximately every 48 hours; in cases of spontaneous abortion, levels typically decrease. Therefore, the most likely cause of this patient’s low β-hCG level is ectopic pregnancy. Risk factors include pelvic inflammatory disease and prior pelvic surgery.
Despite its extrauterine location, an ectopic pregnancy changes the uterine endometrium due to the secretion of β-hCG, which signals the ovarian corpus luteum to continue progesterone production. Progesterone promotes endometrial remodeling and decidualization, which normally optimizes the intrauterine environment for pregnancy. Therefore, if uterine curettage is performed on this patient, it would likely show dilated, coiled endometrial glands and vascularized, edematous stroma (ie, decidualization) but no products of conception (eg, villi).
(Choice A) Atypical endometrial cells with disorganized glands and multiple mitoses are consistent with endometrial adenocarcinoma, a uterine malignancy that usually presents with vaginal bleeding. However, it typically affects postmenopausal women and is not associated with positive β-hCG levels.
(Choice C) Inflammatory infiltration of endometrial glands suggests endometritis, an infection of the uterine decidua. Endometritis is not associated with abnormal β-hCG levels.
(Choice D) Straight, short endometrial glands with compact stroma are found in the early proliferative phase of the menstrual cycle (ie, 4-7 days following menses, prior to ovulation).
Educational objective:
Ectopic pregnancy should be suspected in patients with a pregnancy of unknown location (ie, no visible intrauterine gestation) and abnormally rising β-hCG levels. Despite their extrauterine location, ectopic pregnancies promote endometrial decidualization, which appears as dilated, coiled endometrial glands and vascularized, edematous stroma.
