Maternal-Fetal Physiology and Placentation Flashcards
A 29 yo Caucasian primigravida is 20 weeks pregnant with twins. Today, on her routine U/S for fetal anatomy, she found out that she is carrying two boys. In this patient’s case, which of the following statements correctly describes the zygosity of this pregnancy?
a. The twins must be monozygotic since they are both the same gender.
b. If division of these twins occurred after formation of the embryonic disk, the twins will be conjoined.
c. She has a higher incidence of having monozygotic twins because she is Caucasian.
d. If the U/S showed two separate placentas, the twins must be dizygotic.
e. If the U/S showed two separate placentas, teh twins cannot be monozygotic.
b. If division of these twins occurred after formation of the embryonic disk, the twins will be conjoined.
These twins of the same gender could be monozygotic or dizygotic. Two identifiable chorions can occur in monozygotic or dizygotic twinning. Dizygotic twins will always have two amnions and two chorions, since they result from fertilization of two eggs. Therefore, dizygotic twins may be of the same or different genders. The placentas of dizygotic twins may be totally separate, or intimately fused, depending on the location of the implantation of teh two zygotes.
Monozygotic twins are always of the same gender because they originate from the division of one zygote; however, they may be monochorionic or dichorionic depending on when the separation of the twins occurred.
20-30% of monozygotic twins have dichorionic, diamniotic placentation (similar to dizygotic twins), which results from separation of the blastocyst within the first 72 hours after fertilization. Division that occurs between days 4 and 8 will result in monochorionic, diamniotic twins. 1% of monozygotic twins will be monochorionic, monoamniotic, which occurs with division after day 8 but before the embryonic disc is formed.
Conjoined twins are always monozygotic, and occur with late division after formation of the embryonic disk.
After delivery of a term newborn with Apgar scores of 2 at 1 min and 7 at 5 min, you ask that blood from the umbilical arteries be collected for pH. What do the umbilical arteries carry?
Deoxygenated blood to the placenta
Umbilical arteries atrophy and obliterate within 3-4 days after birth; remnants are called umbilical ligaments
How to continue care with a patient who’s baby has a single umbilical artery?
She will require periodic assessments of fetal growth.
The finding of SUA in the absence of other abnormalities does not require karyotype evaluation, early delivery, or delivery by cesarean. The timing and mode of delivery may be determined by routine obstetric indications. Patients with a fetus with SUA should undergo periodic growth assessments with U/S, as there is an increased risk of growth restriction in these fetuses.
A healthy 25 yo G1P0 at 37 weeks’ gestational age comes to your office to see you for a routine obstetric visit. She reports that on several occasions she has experienced dizziness, light-headedness, and feeling as if she is going to pass out when she lies down on her back to take a nap. What is the most appropriate plan of mgmt for this pt?
a. Perform an electrocardiogram
b. Monitor her for 24 hours with a Holter monitor to r/o arrhythmia
c. Perform an ABG analysis
d. Refer her to a cardiologist
e. Reassure and encourage her not to lie flat on her back
e. Reassure and encourage her not to lie flat on her back
Late in pregnancy, when the mother assumes the supine position, the gravid uterus compresses the IVC and decreases venous return to the heart. This results in decreased CO and symptoms of dizziness, light-headedness, and syncope. This significant arterial hypotension resulting from IVC compession is known as supine hypotensive syndrome or IVC syndrome. No need for additional workup.
A 22 yo primigravida presents to your office for a routine OB visit at 34 weeks’ gestational age. She voices concern b/c she has noticed an increasing number of spidery veins appearing on her face, upper chest, and arms. She is upset with the unsightly appearance of these veins and wants to know what you recommend to get rid of them. How should you counsel this pt?
Vascular spiders, or angiomas, are common findings during pregnancy. They form as a result of the hyper-estrogenism associated with normal pregnancies and are of no clinical significance. The presence of these angiomas does not require any additional workup or treatment, and they will resolve spontaneously after delivery. Reassurance to the patient is all that is required.
What is contraindicated in a pt with placenta previa?
Digital cervical exam
A healthy 34 yo G1P0 pt comes to see you in your office for a routine OB visit at 12 weeks’ gestational age. She tells you that she has stopped taking her prenatal vitamins with iron supplements b/c they make her sick and she has trouble remembering to take a pill every day. A review of her prenatal lab tests reveals that her hematocrit is 39%. What is the best way to counsel her?
Tell the pt that she needs to take iron supplements, even though she is not currently anemic, in order to meet the iron demands of pregnancy.
The amount of iron that can be mobilized from maternal stores and obtained from the diet is insufficient to meet the demands of pregnancy. A pregnant woman with a normal hematocrit at the beginning of pregnancy who is not given iron supplementation will develop iron deficiency during the latter part of gestation, as iron requirements increase significantly during the second half of pregnancy.
It is important to remember that the fetus will not have impaired hemoglobin production, even in the presence of maternal anemia, because the placenta will transport the needed iron at the expense of maternal iron store depletion.
The hematocrit in pregnancy normally falls in pregnancy due to plasma volume expansion and therefore is not used as a parameter to determine when to begin iron supplementation.
A 19 yo P0 at 20 weeks’ gestation presents to the ED with complaints of R flank pain. The ED physician orders a renal sonogram as part of a workup for a possible kidney stone. The radiologist reports that no nephrolithiasis is present, but reports the presence of bilateral mild hydronephrosis and hydroureter, which is greater on the R side than on the L. What is the most appropriate next step in mgmt?
These findings are consistent with normal pregnancy and are not of concern. No further evaluation is required.
When the gravid uterus rises out of the pelvis after 12 weeks, it presses on the ureters at the pelvic brim, causing ureteral dilatation and hydronephrosis. It is also likely that hormonal effect from progesterone contributes to the development of hydroureter and hydronephrosis of pregnancy.
In the vast majority of pregnant women, the ureteral dilatation tends to be greater on the R side as a result of dextrorotation of the uterus and/or cushioning of the L ureter provided by the sigmoid colon.
Why is trace glucosuria a common finding in pregnancy?
During pregnancy, there is an increase in GFR and a decrease in tubular reabsorption of filtered glucose. In fact, one in six women will spill glucose into the urine during pregnancy.
If the pt has risk factors for gestational diabetes, such as obesity, previous macrosomic baby, advanced maternal age, or family hx of diabetes, the physician may want to screen for diabetes with a glucose challenge test.
If the pt has a UTI, the dipstick will be more likely to show an increase in WBcs, and the presence of nitrites and blood.
A 29 yo G1P0 at 28 weeks’ gestation presents to your office complaining of SOB that is more intense with exertion. She has no significant PMH and is not on any medication. The patient denies any chest pain. She is concerned because she has always been very athletic and cannot maintain the same degree of exercise that she was accustomed to prior to becoming pregnant. On physical exam, her pulse is 72 bpm. Her BP is 90/50 mm Hg. Cardiac exam is consistent with grade I systolic ejection murmur. The lungs are clear to auscultation. Which of the following is the most appropriate next step in mgmt of this pt?
Reassure the pt.
The pt’s symptoms and exam is most consistent with physiologic dyspnea, which is common in pregnancy. The increased awareness of breathing that pregnant women experience can occur as early as the end of the first trimester, and is caused by an increase in lung tidal volume. The increase in minute ventilation that occurs during pregnancy may make patients feel as if they are hyperventilating, and may also contribute to the feeling of dyspnea. The patient in this case needs to be reassured and counseled regarding these normal changes of pregnancy.
Systolic ejection murmurs are common findings in pregnant women and are caused by the normal increased blood flow across the aortic and pulmonic valves.
A 22 yo G3P2 undergoes a normal spontaneous vaginal delivery without complications. The placenta is spontaneously delivered and appears intact. The patient is later transferred to the postpartum floor where she starts to bleed profusely. Physical exam reveals a boggy uterus and a bedside sonogram indicates the presence of placental tissue.
What type of placenta?
Succenturiate placenta
Characterized by one or more smaller accessory lobes located in the membranes at a distance from the main placenta.
A retained succenturiate lobe may cause uterine atony and result in postpartum hemorrhage.
A 34 yo G6P5 presents to L&D by ambulance at 33 weeks’ gestational age complaining of the sudden onset of profuse vaginal bleeding.
The patient denies any abdominal pain or uterine contractions. She denies any problems with her pregnancy to date but has had no prenatal care. She admits to smoking several cigarettes a day, but denies any drug or alcohol use. The fetal HR tracing is normal. There are no contractions on the tocometer.
What type of placenta?
Placenta previa
In placenta previa, the placenta is located very near or over the internal cervical os. Painless hemorrhage can occur without warning, and is caused by tearing of the placental attachments during formation of the lower uterine segment in the third trimester, or with cervical dilation during term or preterm labor. A hx of previous cesarean delivery, grand multiparity, and maternal smoking have been associated with an increased risk of placenta previa.
