ULTRASONOGRAPHY IN REPRODUCTIVE MEDICINE
Deborah Smith, M.D.
Ultrasound is one of the most important technologic advancements in the modern practice of Reproductive Medicine. The understanding of pelvic anatomy and physiology aids in the diagnosis of certain disorders associated with gynecology.
Early Landmarks in Normal and Abnormal Pregnancy
Gestational sac: A sonographic term not an embryologic term. Early investigators spoke of a "double decidual sac" sign wherein it was believed that the two layers of the deciduas (capsularis and parietalis) had to be present to make a definitive diagnosis of an intrauterine pregnancy.1 Others believed the diagnosis of an intrauterine pregnancy should not be made until a fetal pole was seen in the developing sac. The echogenic rim in an intrauterine pregnancy is now known to be the result of the trophoblastic decidual reaction that occurs as the primary villi (fetal origin) invade the maternal deciduas. A gestational sac should be seen by transvaginal ultrasound by the time the βhCG >2000 mIU/mL.
Yolk sac: After the appearance of the gestational sac the next structure visible sonographically is the yolk sac. It is first visible 3-3 1/2 weeks postconception (=5-5 1/2 weeks AOG). It is fetal in origin and extra-amniotic. The yolk sac is about 4 mm in diameter and is visible and constant until about 10 weeks AOG. Enlarged yolk sacs >5 mm are associated with an increased risk of pregnancy loss or chromosomally abnormal fetus. The yolk sac should be seen by transvaginal ultrasound by the time the βhCG level >8000 mIU/mL.
Embryonic (Fetal) Pole: First seen between 5-6½ weeks AOG the embryo grows about 1 mm/day. Cardiac activity is generally seen when the embryo measures 5 mm or greater but this greatly depends on the resolution of the ultrasound equipment. The actual HR is slow until 10 weeks when it is >120 beats/minute and at 8 weeks AOG when it increases to 140-160 beats/minute. FHR <90 beats/minute at 6 weeks AOG have a 70% spontaneous loss rate. FHR should be seen by the time the βhCG level is >11,000 mIU/mL.4
Blighted Ovum/Missed Abortion
- Blighted ovum initially defined as gestational sac >20 mm without an embryo (using abdominal ultrasound). It now appears that once a gestational sac is >10 mm (inner to inner wall) a yolk sac should be visualized and if it is not visualized it is usually a nonviable pregnancy (scanning skill important!).
- Missed abortion was previously defined as embryo >15 mm without cardiac activity but has not passed spontaneously. Now with transvaginal technique embryonic heart motion should be seen when the embryo is >10 mm in size.
Subchorionic hemorrhage: Seen in 20% of pregnancies that have vaginal bleeding.
- Crescent shaped sonolucent collections outside of the gestational sac.
- Those patients with vaginal bleeding in pregnancy and ultrasound reveals fetal cardiac activity and no subchorionic bleed have a 98% continuation rate.
- Those patients with vaginal bleeding in pregnancy and ultrasound reveals fetal cardiac activity and a subchorionic bleed have a 70% continuation rate.
- 60% of twin gestations diagnosed prior to 10 weeks will be singleton by term.
- Better to diagnose with endovaginal probe.
- Can be diagnosed earlier with TVUS.
- Incidence 1 in 100 pregnancies.
- Suspect when--No double ring, irregular "sac", no embryonic structures in sac.
Menopause and Ultrasound
- Postmenopausal mass
- Ovary- In postmenopausal women:
- If the ovarian mass is <5 cm, 3% risk that it is cancer.
- If the ovarian mass is 5-10 cm in size, 15% risk that it is cancer.
- If the ovarian mass is >10 cm in size, 65% risk that it is cancer.
- Scoring system for ovarian masses.
- Fibroids - monitor size and location
- Polyps - may be better visualized with a fluid contrast ultrasound
- Endometrium - especially useful for evaluation for abnormal uterine bleeding in postmenopausal women. Remember these criteria are for postmenopausal women not regularly cycling pre-menopausal women.
- Endometrial hyperplasia/carcinoma
- >5 mm - increased risk there is an abnormality of the endometrium (polyp, hyperplasia)
- >8 mm - increased risk that there is hyperplasia or carcinoma
- Transvaginal ultrasound evaluation of the endometrial lining of postmenopausal women with abnormal bleeding has decreased the incidence of surgical intervention (Bx or D&C) by 60%.
Role of Ultrasound in Ovulation Induction
Sequential use of ultrasound for monitoring follicular size and the endometrial stripe.
Clomiphene Citrate: Follicle average diameter >19 mm used for timing insemination and hCG injections.
Human Menopausal Gonadotropins: Follicle average diameter >16 mm for timing hCG injection and intrauterine insemination
In Vitro Fertilization: For determining follicle number and maturity typically >18 mm. There is a high correlation between the number of oocytes aspirated and the number of follicles visualized by ultrasound.
Frozen Embryo Transfer: For endometrial stripe measurement. >8 mm higher chance of success.
Oocyte Retrieval: Usually done under ultrasound guidance. Better oocyte recovery when compared to laparoscopic or transvesical retrieval.
Embryo Transfer: Higher success with abdominal ultrasound-guided embryo placement procedures.
Multifetal pregnancy reduction
Ultrasound-Guided Tubal Cannalation: For gametes for insemination technique or GIFT technique.
- Endometrial Pattern and Pregnancy Success: Triple line pattern measuring >8mm just prior to ovulation is associated with the highest pregnancy rates during ovulation induction
Sonohysterogram (Fluid Contrast Ultrasound)
- Catheter: Several catheters are available commercially for the sonohysterography procedure. There are both disposable and reusable catheters. Some catheters have a balloon tip, others have cone tips for occluding the cervical os.
- Fluid: Sterile water saline or lactate ringers, 60 cc.
- Syringe: Leur lock
- Betadine swabs
- Tenaculum, ring forceps, dilators: Hopefully these will not be needed, but occasionally it is difficult to pass the catheter.
- Preoperative antibiotics are not necessary
- NSAID one hour prior to the procedure reduced cramping
- Insert catheter through the cervical os using sterile technique
- Instill 5-30 cc of sterile fluid
- Visualize the uterine cavity longitudinally then transversely
- If using a balloon tip, deflate the balloon after instilling the fluid to visualize the cavity completely
Ovarian Changes Associated with Infertility
Endometriosis: Sometimes endometrioma can be seen by ultrasound. Endometrioma larger than 3 cm in size rarely respond to medical therapy. Therefore, ultrasound may be utilized to determine if surgical or medical therapy is the best option, in addition to making the diagnosis. Women with endometriosis have a higher incidence of infertility.
- Ardaens et al (Fertil Steril 1991; 55:1062
- Uterine widths/ovarian length ratio <1
- Ovarian width/ovarian length ratio >0.7
- Small echoless regions (follicles) <8 mm in size on a single ovarian slice >10
- Hyperechogenic central ovarian stroma
- Pache et al (Fertil Steril 1993; 59:544-549)
- Small echoless regions (follicles) <8 mm in size on a single ovarian slice >10
Ovarian volume/antral follicle count
- Ovarian volume - larger the size the better response to ovulation induction
- Antral follicle count - number of follicles <10 mm in each ovary around CD 2-5. Antral follicle counts >10 predict better response to superovulation and thus higher chance of achieving pregnancy. Useful for determining dose of fertility medication and protocol.
- Color Doppler and Reproductive Medicine
- Monitor response to therapy
Aspirin therapy in IVF
- Danazol increases impedance to uterine circulation and hence reduces uterine blood flow.
- Improve blood flow to ovary and uterus as demonstrated by changes in the uterine pulsatility index and ovarian pulsatility index. Demonstrating aspirin improves uterine and ovarian blood flow.
- Patients with improvement in uterine and ovarian blood flow during the cycle of stimulation as determined by the pulsatility index had higher pregnancy rates in ovulation induction and IVF.
1. Bradley et al: The double sac sign of early intrauterine pregnancy: Use in exclusion of ectopic pregnancy. Radiology 143:223-226, 1982.
2. Sauerbrei E, Coopersberg PL, Poland JB: Ultrasound demonstration of the normal fetal yolk sac. J Clin Ultrasound 8:217, 1980.
3. Nyberg DA, Filly RA, Mahony BS: Early gestation: Correlation of hCG levels and sonographic identification. AJR 144:451, 1985.
4. Bree RL, Edwards M, Bohen Velez M et al: Transvaginal sonography in the evaluation of normal early pregnancy; Correlation with hCG levels. AJR 153:75-79, 1989.