Ultrasound
Vincenzo Berghella in Obstetric Evidence Based Guidelines, 2022
A gestational sac is normally noted within the uterus by 5 weeks of gestation. Shortly thereafter at approximately 5 ½ weeks in a normal pregnancy, the yolk sac appears, followed by the fetal pole at 6 weeks. When measuring the gestational sac, dimensions are recorded in three orthogonal planes; the average of the measurements is the mean sac diameter. A mean gestational sac diameter of ≥25 mm without an embryo is diagnostic of pregnancy failure (e.g. anembryonic pregnancy, or blighted ovum) with positive predictive value approaching 100% [21] (See also Chap. 16). An intrauterine gestational sac should be visible by transvaginal ultrasound with a serum beta-human chorionic gonadotropin (B-hCG) of >1500 mIU/mL. If this is not the case, ectopic pregnancy should be suspected.
New imaging diagnostics
Carlos Simón, Linda C. Giudice in The Endometrial Factor, 2017
Transvaginal US is the primary imaging modality for evaluation of an early intrauterine pregnancy. In normal pregnancies, the gestational sac is usually seen at 4.5 weeks’ gestation as an oval or rounded sonolucent area surrounded by a hyperechogenic double rim measuring at least 2 mm in thickness (13). Color Doppler allows visualization of the embryonic heart activity when crown–rump length (CRL) reaches between 2 and 4 mm (Figure 2.8a). 3-D sonography enables precise volume measurement of the gestational sac during the first trimester (Figure 2.8b). Surface rendering may be beneficial in the evaluation of the yolk sac echogenicity, which is commonly associated with chromosomal abnormalities (28,29). Sonographic and color Doppler assessment of the uterine cavity after pregnancy loss or termination is very useful for detection of residual products of conception (RPOC). Bright color signals coupled with the low resistance flow just beneath the endometrium or within the myometrium are a sensitive indicator of RPOC (Figure 2.9). Table 2.2 reviews typical sonographic and color and pulsed Doppler findings of abnormal pregnancy or pregnancy complications, such as anembryonic pregnancy, missed abortion, RPOC, arteriovenous malformation, molar pregnancy, and choriocarcinoma (30–34).
Seeing with Sound: Diagnostic Ultrasound Imaging
Suzanne Amador Kane, Boris A. Gelman in Introduction to Physics in Modern Medicine, 2020
A normal pregnancy lasts 40 weeks on average; by convention, gestation is divided into three roughly three-month-long periods called trimesters. Obstetrical ultrasound imaging can be performed any time after approximately the fifth week of pregnancy, at which point the gestational sac is visible in the uterus, although more information is gleaned the further along the pregnancy is. Early ultrasound can confirm the pregnancy, and distinguish between normal and abnormal pregnancies (such as a “blighted ovum” in which no fetus can be seen in the amniotic sac). By about seven weeks, the fetal heart motion is visible, and the broad outlines of the developing fetus can be resolved (Figure 4.20b). Later exams can distinguish in great detail many anatomical features of the fetus and placenta.
Early Pregnancy Losses: Review of Nomenclature, Histopathology, and Possible Etiologies
Published in Fetal and Pediatric Pathology, 2018
M. Halit Pinar, Karen Gibbins, Mai He, Stefan Kostadinov, Robert Silver
To be able to interpret the abnormal findings in miscarriage specimens, it is important to review the morphology of normal early gestation. The basic structure of an early gestation is the gestational sac. In the early stage of development, the trophoblastic villi form all around the embryo and give it the appearance of a hairy ball. (Figure 1) illustrates normal chorionic villi from an elective termination at 6 weeks' gestation. After week 8, most placental villi disappear but remain present at the decidual plate. The chorion in this location becomes villus rich and is called chorion frondosum. At other locations, where the villi degenerate, the chorion becomes smooth (chorion laeve). This fuses with the placental membranes, and, at these locations, no exchange between the maternal and fetal blood circulation systems takes place. The embryo is located inside two sacs, called amnionic and chorionic sacs. (Figure 2) illustrates the structure of an early gestational sac. (Figure 3) illustrates more detailed morphology of an elective termination from a normal gestation.
Further evidence that a supraphysiologic estradiol level during ovarian stimulation affects birthweight: findings of fresh and frozen embryo transfer with comparable estradiol levels on human chorionic gonadotropin trigger
Published in Gynecological Endocrinology, 2021
Lu Luo, Huiying Jie, Minghui Chen, Limei Zhang, Yanwen Xu
For FET cycles, endometrium was prepared with natural cycles or hormone replacement cycles. For natural cycles, embryos were transferred on the third (for D3 embryos) or fifth (for blastocysts) day after ovulation. Hormone replacement therapy for hormone replacement cycles was initiated on days 3–5 of a spontaneous menstrual cycle or 3–5 days after progesterone withdrawal bleeding. The initial dose of estradiol valerate was 2 mg twice per day. Vaginal ultrasound and hormone assays were performed to adjust the dosage. If the endometrial thickness reached 8 mm and the serum E2 level reached 100 pg/mL, oral E2 was continued and an intramuscular injection of 40 mg progesterone was given for two days, followed by 60 mg for the following 15 days. Embryos were transferred on the fourth or sixth day of progesterone treatment. Pregnancy tests were conducted 12 days after ET. Clinical pregnancy was defined as intrauterine gestational sac observed at 7 weeks of gestation.
Extended culture of cleavage-stage embryos in vitrified–thawed cycles may be an alternative to frozen and thawed blastocysts during in vitro fertilization
Published in Gynecological Endocrinology, 2022
Pinar C. Aytac, Esra B. Kilicdag
Pregnancy was defined as a human chorionic gonadotrophine (HCG) level higher than 10 IU/l noted 10 days after embryo transfer. If the HCG level then doubled two days later, patients were evaluated by transvaginal ultrasound to check gestational sac and fetal heart beat in two weeks time. A clinical pregnancy was defined as a gestational sac in uterus around 6th or 7th week of gestation. If HCG levels did not increase properly, one week later we examined our patient to rule out ectopic pregnancy versus chemical abortus. Pregnancy rate was defined as a positive pregnancy tests per IVF cycle, while clinical pregnancy rate was defined as a positive gestational sac per IVF cycle. Live birth rate was defined as the number of live born babies per 100 embryo transfers. Chemical abortus was noted if HCG levels decreased and no gestational sac was seen in the uterus. Implantation ratio was defined as a ratio of the number of gestational sacs over the number of transferred embryos. Abortus was defined as gestational sac without fetal heart beat or expulsion of gestational sac with vaginal bleeding before 20 weeks of gestation. Early abortus was defined as a pregnancy not proceeding beyond 12 weeks of gestation, while late abortus was a pregnancy ending between 12 and 20 weeks of gestation.
Related Knowledge Centers
- Embryo
- Uterus
- Pregnancy
- Obstetric Ultrasonography
- Echogenicity
- Gestational Age
- Trilaminar Embryonic Disc
- Amniotic Sac
- Conceptus
- Heuser'S Membrane