A 37-year-old woman, gravida 2 para 0 aborta 1, at 8 weeks gestation comes to the emergency department due to 2 days of light vaginal spotting and mild abdominal cramping. She has not passed large clots or had heavy bleeding. The patient has infertility issues and this pregnancy resulted from an ovulation induction. Her only prior pregnancy was an ectopic pregnancy 10 years ago that was treated with methotrexate. She has no other medical conditions. The patient takes a daily prenatal vitamin and does not use tobacco, alcohol, or illicit drugs. Blood pressure is 116/64 mm Hg and pulse is 76/min. BMI is 26 kg/m². Speculum examination shows a closed cervix and scant blood in the vagina. Bimanual examination reveals a 10-week-sized nontender uterus and no adnexal masses or tenderness. Two 8-week intrauterine gestations with normal heartbeats are seen on ultrasound. There is a single placenta and no dividing intertwin membrane. Which of the following is the most likely diagnosis in this patient?

Question

Quizplus · Accepted Answer

11ec25c8_da4a_e11c_bc81_bdffe591d0b9_MD0003_00 Vaginal spotting and mild abdominal cramping are common during the first trimester and normal in patients with a closed cervix and a viable intrauterine gestation. This patient has 2 viable intrauterine gestations, or twin pregnancy. Twin pregnancies are classified based on chorionicity (number of placentas) and amnionicity (number of amniotic sacs); this is best assessed during the first trimester, as the imaging is not obscured by the growing fetuses and resultant overcrowding. Management of twins is dependent on chorionicity and amnionicity, as complications differ depending upon the classification. This patient's twin gestation has a single placenta and no dividing intertwin membrane (ie, single amniotic sac), consistent with monochorionic monoamniotic twins. Monochorionic monoamniotic twins are the least common of twin gestations and have the highest pregnancy-related complication rate. In addition to complications that occur in all twins (eg, preterm birth), the single placenta increases the risk of twin-twin transfusion syndrome (unbalanced arteriovenous anastomoses), and the single amniotic sac increases the risk for umbilical cord entanglement and intrauterine fetal demise. Therefore, monochorionic monoamniotic twins are typically managed inpatient beginning at 28 weeks gestation with frequent fetal monitoring (eg, nonstress test) and antenatal corticosteroid administration. Patients are delivered preterm (32-34 weeks gestation) via cesarean delivery. (Choice A) Dichorionic diamniotic pregnancies have 2 placentas and 2 amniotic sacs. However, due to fetal overcrowding, some dichorionic diamniotic twins develop an obscured intertwin membrane that causes the separate placentas to have a single, fused appearance on ultrasound (similar to monochorionic diamniotic twins). However, dichorionic diamniotic gestations with a "fused" placenta can be identified by a thick intertwin membrane and a placental projection where the intertwin membrane meets the placenta (ie, lambda-sign). lambda-sign (Choice B) A heterotopic pregnancy is the presence of both an intrauterine and an ectopic (ie, extrauterine) pregnancy, which are not seen in this patient. (Choice C) An inevitable abortion presents with vaginal bleeding and abdominal pain; however, patients also have a dilated cervix, making this diagnosis unlikely. (Choice D) Monochorionic diamniotic twins have a single placenta and 2 amniotic sacs with a thin intertwin membrane that meets the placenta at a 90-degree angle (ie, T-sign). T-sign Educational objective: A monochorionic monoamniotic twin pregnancy has a single placenta and no intertwin membrane on ultrasound. Monochorionic monoamniotic twin pregnancies are at risk of cord entanglement and fetal demise; therefore, patients require inpatient monitoring. Delivery typically occurs by 32-34 weeks gestation via cesarean delivery. References: Role of ultrasonography in the management of twin gestation. (http://www.ncbi.nlm.nih.gov/pubmed/29536536) First-trimester ultrasound determination of chorionicity in twin pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/21308842) Managing monoamniotic twin pregnancies. (http://www.ncbi.nlm.nih.gov/pubmed/26083132)

A 37-Year-Old Woman, Gravida 2 Para 0 Aborta 1, at 8