Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
PLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2. With attachment of the blastocyst to the endometrial cavity, the trophoblastic cells differentiate into an inner layer; the cytotrophoblasts and an outer layer; the syncytiotrophoblasts. The syncytiotrophoblasts develop lacunae forming early intervillous spaces.The placenta forms at the site of th Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2e chorion frondosum (the fetal portion of chorion) and the decidua basalts and is first recognized sonographically as a thickened echogenic region byEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
about 9-10 weeks of gestation (Figure 8.1). Maternal blood flow is established within the placenta by 12 weeks of gestation (1). The placenta at term PLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2ogic conditions and thus assessment of the biometric dimensions of the placenta are infrequently performed on prenatal sonography today. The normal thickness of the placenta is correlated to gestational age with approximately 1 mm per weeks of gestation (3).Figure 8.1: Ultrasound of an intrauterine Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2pregnancy at 9 weeks showing the echogenic placenta (labeled). Note the decidua basalis (labeled) as a hypoechoic region behind the placenta. The embrEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
yo is also shown (labeled).chapter S: Pincental AbnormalitiesPlacental localization by ultrasound is one of the six components of the standardized appPLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2focus on the ultrasound diagnosis of placental abnormalities.PLACENTA PREVIAThe term placenta previa describes a placenta that covers part or all of the internal cervical OS. In normal pregnancy, the placenta implants in the upper uterine segment. In the case of placenta previa, the placenta is part Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2ially or totally implanted in the lower uterine segment.Placenta previa is one of the most common causes of bleeding in the second and third trimesterEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
of pregnancy. The incidence of placenta previa in the United States at term is estimated at 4.8'1000 deliveries (4). Given that there is a positive aPLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2nce of multiparity. The classical presentation of placenta previa is painless vaginal bleeding in the late second and third trimester of pregnancy. Painful bleeding may occur in some pregnancies with placenta previa however due to the association with uterine contractions or placental separation (ab Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2ruption). The first presentation of placenta previa maybe bleeding during labor which highlights the critical importance of prenatal diagnosis and a pEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
lanned delivery by cesarean section if the placenta previa persists into the third trimester of pregnancy. Placenta previa is also associated with a hPLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2early gestation (Figure 8.2). and in many such cases, with advancing gestation and growth of the uterus, the placenta is lifted into the upper uterine segment. This mechanism of "placental shift, migration" is poorly understood but may be related to a preferential growth of the placental towards a b Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2etter-vascularized upper endometrium (tropho tropism).Chapter S: Placenta! AbtwnnahtiesFigure 8.2: Ultrasound of an intrauterine pregnancy at 13 weeksEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
. Note that the placenta (labeled) is covering the internal os of the cervix (labeled), representing a placenta previa.Table 8.1 lists risk factors foPLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2of four prior cesarean sections increases the incidence of placenta previa about 10 folds (5).TABLE 8.1 Risk Factors for Placenta PreviaHistory of prior cesarean deliveryPrior pregnancy termination(s)-Prior uterine surgery-Maternal smokingAdvanced maternal ageMultiparityCocaine use in mother-Multipl Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2e pregnancyChipter S: Plncait.il Abtx>nn.ihticsissThe current terminology used to describe types of placenta previa has been somewhat confusing. ComplEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
ete placenta previa describes a placenta that completely covers the internal OS. a partial placenta previa describes a placenta that partially covers PLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2 distance away from the internal OS. within a few cm( s). the term low-lying placenta is suggested, and the distance should be measured. Assessing a dilated cervix by ultrasound for the diagnosis of partial previa is difficult, if not impossible, and the distance used to designate a low-lying placen Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2ta has been variable in the literature. Recently, a multi-disciplinary consensus conference in the United States has suggested a simpler terminology oEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
f placenta previa that is more pertinent and clinically applicable (6). This new classification uses 3 terms only: placenta previa, low-lying placentaPLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2e and total placenta previa should also be eliminated.The new classification is as follows: for pregnancies at less than 16 weeks of gestation, diagnosis of placenta previa is overestimated. For pregnancies greater than 16 weeks, if the placental edge is >2 cm from the internal OS. the placental loc Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2ation should be reported as normal. If the placental edge is < 2 cm from the internal OS. but not covering the internal OS. the placenta should be labEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
eled as low-lying (Figure 8.3 ) and a follow-up ultrasound is recommended at 32 weeks. If the placental edge covers the internal cervical OS. the placPLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2 if the placental edge is still less than 2 cm from the internal cervical OS (low-lying) or covering the cervical os (placenta previa), a follow-up transvaginal ultrasound is recommended at 36 weeks (6). These recommendations are for asymptomatic women and an earlier follow-up ultrasound may be indi Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2cated in the presence of bleeding. Because low-lying placenta or placenta previa detected in the mid second trimester that later resolves in pregnancyEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
is associated with vasa previa, transvaginal ultrasound with color, pulsed Doppler in the third trimester (around 32 weeks) is recommended to rule-ouPLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2ll bladder and / or a uterine contraction of the lower uterine segment can potentially result in a false positive diagnosis of a placenta previa, when a transabdominal approach is used. The transvaginal approach allows for a clear evaluation of the internal cervical os and the exact anatomic relatio Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2n of the placental edge to the cervix. Furthermore, color Doppler, when available, can assess the vascularity of the placenta, cervix and lower uterinEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
e segment and evaluate for the risk of accreta and bleeding at delivery (Figure 8.6). The safety of the transvaginal ultrasound approach in the assessPLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2ip of the cervix, unlike a digital examination, which typically introduces a fingerChapter S: Pincental Abiwnnahtiei1SÔinto the cervical canal. Figure 8.7. x.x and X.9 show normal anterior, ftindal and posterior placentas respectively.Figure 8.3: Transvaginal ultrasound in the third trimester showin Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2g a low-lying posterior placenta {labeled). Note that the lower edge of the placenta is about 0.9 cm from the cervical internal OS {labeled). The cervEbook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2
ix is also labeled for image orientation.Figure 8.4: Transvaginal ultrasound in the third trimester showing a placenta previa. Note that the placenta PLACENTAL 8ABNORMALITIESINTRODUCTIONThe placenta develops from the trophoblast cell layer of the blastocyst embryo at about 6 days from fertilization. Ebook Ultrasound in obstetrics and gynecology - A practical approach (1/E): Part 2hapter S: Placental AbnormalitiesGọi ngay
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