Tetraploidy

NEW YORK -- A diagnostic work-up is indicated when a woman has had at least three first-trimester spontaneous abortions or just one pregnancy loss in the second or third trimester. Dr. Anthony Vintzileos said at an obstetrics symposium sponsored by Columbia University and New York Presbyterian Hospital.

If the mother is older than 35, a work-up should be done after two first-trimester losses or one subsequent loss, added Dr. Vintzileos, professor and acting chair of the department of obstetrics, gynecology, and reproductive sciences at Robert Wood Johnson Medical School. New Brunswick, N.J.

Data suggest that the overall chance of a second pregnancy loss after just one first-trimester loss is about 13.5%, not much higher than the 13% rate among those with no previous pregnancy losses. Among those with two first-trimester losses--occurring in about 5% of all couples--the recurrence rate increases to about 25%, and up to 33% with at least three losses.

The recurrence rate is elevated 5- to 20-fold after just one pregnancy loss during the second or third trimester, however.

The rates of pregnancy loss decrease with increasing gestational age, from 55% during preimplantation (0-6 days gestation) to 25% at 7-13 days to 8.2% by 14-20 days and to below 1% by 18-21 weeks. And as those rates drop, the most common causes for the losses change. That's why the textbook definition of "recurrent early pregnancy loss" as at least three spontaneous abortions occurring before 20-22 weeks doesn't really make sense, he said.

"Losses prior to 20-22 weeks have a diverse etiology. [This definition] doesn't help in managing the patient," he said.

Sonohysterography/hysteroscopy and a review of placental/fetal pathology are indicated for work-up in all cases of recurrent pregnancy loss. For repeated first-trimester losses, parental karyotyping and testing of ovarian function should also be part of the evaluation.

For repeat losses during the second or third trimester, testing for congenital thrombophilia should be part of the work-up when there is evidence of fetal growth restriction, oligohydramnios, or extensive placental thrombosis, while losses due to intraamniotic infection or cervical incompetence require surveillance for mycoplasma, bacterial vaginosis, and trichomonas during subsequent pregnancies, he advised.

Chromosomal abnormalities are the most common cause of first-trimester losses, with a prevalence of greater than 50%. Among the genetic factors accounting for first-trimester pregnancy losses, 50% are autosomal trisomies, 20-25% are monosomies, 16% are triploidy, and 8% tetraploidy. It's estimated that in 2%-3% of couples with recurrent first-trimester pregnancy loss, one of the partners has a balanced translocation.

Data suggest that chromosomal abnormalities are responsible for approximately 70% of all first-trimester pregnancy losses but only 22% of losses in the second trimester (Am. J. Obstet. Gynecol. 189[2]:397-400, 2003). In that study, aneuploidy was found in 82% of first-trimester losses among women aged 35 years and older, compared with just 57% of women under 35. However, those rates were nearly identical for second-trimester losses (21% and 22%, respectively).

Septate uterus, which results in a 60% spontaneous abortion rate, is probably the second leading cause of first-trimester losses. Other uterine anomalies are also associated with high spontaneous abortion rates, including unicornuate (45%), didelphys (42%), and bicornate (30%). Diagnosis is typically made using sonohysterography or hysterosalpingography. Unfortunately, there is no good treatment for most of these conditions, although metroplasty and cerclage have been used with some success, he said.

Impacted uterus, on the other hand, is a different story. An often-missed diagnosis, it should be suspected in any patient with the classic triad: pregnancy loss at 14-16 weeks, retroverted/retroflexed uterus associated with large fibroids and/or adhesions, and normal placental histology. It may or may not be associated with lower pelvic discomfort that is not relieved by positional changes, urinary symptoms, or constipation. Treatment with elevation of the uterus out of the pelvis under adequate analgesia, anesthesia, or even intraabdominal carbon dioxide insufflation used during laparoscopy is often effective, he said.

Abnormal cervical competence should be investigated via transvaginal cervical sonography with fundal pressure at 16-18 weeks in patients with prior midtrimester loss. Management depends on the cervical length: Cerclage is indicated if it's less than 1.6 cm, and should be considered if the cervical length is 1.6-2.0 cm with documented progressive shortening. The cervical length measurement should be repeated at 1 week if 2.1-2.5 cm, 2 weeks for 2.6-3.0 cm, and so on. Bed rest is advised for all patients with cervical lengths less than 2.5 cm.

Intraamniotic fluid infection is another common cause of repeated midtrimester (19-24 weeks) loss, and can mimic cervical incompetence. Indeed, approximately 80% of patients who have a classic history of midtrimester loss will have longstanding mycoplasma, bacterial vaginosis, or trichinosis infections, although the etiologic link has not been proved.

At least one study also found an increased risk for first-trimester (<20 weeks) spontaneous abortion and bacterial vaginosis, Mycoplasma hominis and Ureaplasma urealyticum but not other microorganisms (Am J. Obstet. Gynecol. 183[2]:431-37, 2000).

Antiphospholipid syndrome is probably overrated as a cause of fetal loss. "The textbooks say it responsible for 5%-15% of pathologic pregnancy loss, but I believe it's less, at least in my population." Dr. Vintzileos said. The condition should be suspected, however, in cases of fetal loss in the second or third trimester associated with fetal growth restriction, oligohydramnios, and extensive placental thrombosis.

Heparin plus aspirin is now the treatment of choice, with empiric use of intravenous immunoglobulin as a last resort. Prednisone should not be used, since it is associated with nearly a fivefold increased risk for prematurity (Obstet, Gynecol, 99[1]:135-44, 2002).

Congenital thrombophilias present similarly to antiphospholipid syndrome, and should also be considered in cases of repeat second-trimester loss associated with fetal growth retardation, oligohydramnios, and extensive placental thrombosis.

BY MIRIAM E. TUCKER

Senior Writer

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