A 29-year-old woman, gravida 1 para 0, at 36 weeks gestation comes to the office for a routine prenatal visit. The patient has noticed less fetal movement than normal. She has had no vaginal bleeding, contraction pain, or leakage of fluid. The patient has no chronic medical conditions and takes a daily prenatal vitamin. She previously smoked a pack of cigarettes daily but decreased to a quarter pack daily after becoming pregnant. Her prenatal course has been uncomplicated; a first-trimester ultrasound showed a viable intrauterine pregnancy and multiple intramural and submucosal leiomyomas. Vital signs are normal. Fundal height is 38 cm. A nonstress test is reactive. Ultrasound shows a fetus in frank breech presentation with an estimated fetal weight at the 80th percentile for gestational age, a fundal placenta, and an amniotic fluid index of 15 cm. Which of the following is the most likely cause of this patient's fetal presentation?

Question

A 29-year-old woman, gravida 1 para 0, at 36 weeks gestation comes to the office for a routine prenatal visit.  The patient has noticed less fetal movement than normal.  She has had no vaginal bleeding, contraction pain, or leakage of fluid.  The patient has no chronic medical conditions and takes a daily prenatal vitamin.  She previously smoked a pack of cigarettes daily but decreased to a quarter pack daily after becoming pregnant.  Her prenatal course has been uncomplicated; a first-trimester ultrasound showed a viable intrauterine pregnancy and multiple intramural and submucosal leiomyomas.  Vital signs are normal.  Fundal height is 38 cm.  A nonstress test is reactive.  Ultrasound shows a fetus in frank breech presentation with an estimated fetal weight at the 80th percentile for gestational age, a fundal placenta, and an amniotic fluid index of 15 cm.  Which of the following is the most likely cause of this patient's fetal presentation?

Quizplus · Accepted Answer

11ec25c8_da33_d77c_bc81_ddb79bd19057_MD0003_00 Breech presentation occurs when the fetal buttocks or feet are the closest fetal part to the cervix. It is a common type of fetal malpresentation and has an increased risk of complications during vaginal delivery (eg, delivery trauma, umbilical cord prolapse, head entrapment). Variable fetal presentation, including breech, is normal during early pregnancy due to the small fetal size relative to the amniotic fluid volume; with increasing gestational age, the fetus typically develops a cephalic presentation, thereby optimizing chances of an uncomplicated vaginal delivery. buttocks feet Fetal malpresentation (eg, breech) can occur when either fetal mobility or maternal anatomy (ie, fixation of presenting part in the pelvic inlet) is affected. A common risk factor for breech presentation (as seen in this patient) is uterine leiomyomas, particularly submucosal fibroids, as they can distort the uterine cavity and limit fetal mobility. In addition, large leiomyomas in the lower uterine segment can become space occupying and prevent fetal cephalic engagement. submucosal fibroids Patients with breech presentation and no contraindications to vaginal delivery (eg, placenta previa, prior classical cesarean delivery) can be offered an external cephalic version (manual rotation of the fetus to cephalic presentation) at ≥36 weeks gestation. (Choice A) Polyhydramnios (amniotic fluid index ≥24 cm) and oligohydramnios (amniotic fluid index ≤5 cm) are risk factors for breech presentation because extremes of amniotic fluid volume can cause fetal hypermobility (polyhydramnios) or hypomobility (oligohydramnios). This patient's amniotic fluid index is normal. (Choices B and E) Fetal growth restriction and its causes (eg, tobacco use) are risk factors for breech presentation, as small fetal size can result in hypermobility. Although this patient uses tobacco, fetal weight is normal; therefore, it is not likely the cause of this breech presentation. (Choice C) Multiparity is a risk factor for breech presentation, as pregnancy increases abdominal wall laxity and changes uterine shape in subsequent pregnancies, which can prevent fetal engagement. This patient is nulliparous. (Choice D) Placenta previa is a risk factor for breech presentation because the placenta occupies the lower portion of uterus and prevents fetal engagement. This patient has a fundal placenta. Educational objective: Breech presentation occurs when the fetal buttocks or feet are the closest fetal part to the cervix. A risk factor for breech presentation is uterine leiomyomas, which can distort the uterine cavity, thereby limiting fetal mobility and preventing fetal cephalic engagement. References: Breech presentation at term and associated obstetric risks factors-a nationwide population based cohort study. (http://www.ncbi.nlm.nih.gov/pubmed/28176014) Breech presentation: its predictors and consequences. An analysis of the Hungarian Tauffer Obstetric Database (1996-2011). (http://www.ncbi.nlm.nih.gov/pubmed/26660231) Common determinants of breech presentation at birth in singletons: a population-based study. (http://www.ncbi.nlm.nih.gov/pubmed/24784711)

A 29-Year-Old Woman, Gravida 1 Para 0, at 36 Weeks