Mark I. Evans

SCREENING FOR NEURAL TUBE DEFECTS

Neural tube defects are separated into two main categories: (1) abnormalities of the skull and brain (anencephaly, acrania, and encephalocele) and (2) malformations of the spine (meningomyelocele or spina bifida). The cause of neural tube defects is not always clear, and include chromosomal abnormalities, single gene mutations, maternal disease, or maternal exposure to teratogens. Mostly the disorder emerges as a multifactorial trait. Routine screening for neural tube defects was introduced in the United Kingdom in the mid-1970s and the United States in the mid-1980s. The use of screening has resulted in a marked decline in the frequency of neural tube defects diagnosed at birth.

Intact fetal cells in maternal plasma: are they really there?

Rare fetal cells can be recovered from maternal blood, which suggests that non-invasive prenatal diagnosis is possible. However, recovery and analysis of fetal cells from blood is complex, and sensitivity is low because of the rarity of these cells in the maternal circulation. An alternative strategy, which suggested that intact fetal cells can be found in maternal plasma by use of simple enrichment methods, has been reported. We aimed to replicate this technique. However, five independent laboratories were unable to identify any intact male cells from the plasma of 38 women known to be carrying male fetuses. Although apoptotic intact fetal cells could contribute to the detection of fetal DNA in maternal plasma, we believe that recovery of these cells is difficult and not clinically practical.

Natural History of Twin Gestation Complicated by in utero Fetal Demise: Associations of Chorionicity, Prematurity, and Maternal Morbidity

Objectives: To evaluate the pathophysiology by which the in utero death of 1 twin might increase morbidity to its co-twin survivor and its mother. To assess previously reported risks for maternal disseminated intravascular coagulopathy, peripartal hemorrhage, retained placenta and infection, as well as the fetal risk of prematurity. Material and Methods: A retrospective analysis of the natural history of twin pregnancies from three institutions was performed. A total of 1,989 cases of twin pregnancy were identified, Wayne State University included 1,266 cases from 1984 to 1993; Madigan Army Medical Center 136 cases, 1995–2000, and Rockford Regional Perinatal Center, 587 cases, 1990–2000. The findings were classified by the presence or absence of fetal death in utero (IUFD) as follows: both IUFD (0/0); 1 IUFD (0/+), and both live born (+/+). A case-control study was performed on the subgroup of patients for whom complete records as to chorionicity, etc., were available. Results: Of the 1,989 cases reviewed there were 49 both IUFD (0/0), 61 complicated by 1 IUFD (0/+), and 1,879 with both live born (+/+). The overall fetal death rate for this twin cohort was 55/1,000. IUFD of 1 or both twins was related to an increased risk of previable delivery 55% in 0/0, and 28% in 0/+ versus 4% for +/+ with p < 0.001. IUFD also was associated with early preterm delivery (mean gestational age at delivery of 23 (0/0) and 30 (0/+) versus 35 (+/+) weeks). Chorionicity as well as maternal risks were examined in the case-control study (24 (0/0), 43 (0/+), 134 (+/+)) with the following results: monochorionic placentation was more likely in pregnancies complicated by IUFD (54% (0/0), 51% (0/+) versus 14% (+/+); p < 0.001). Retained placenta, requiring dilation and curettage, occurred more frequently when both twins died in utero, but may be related to the earlier gestational age at delivery. Discussion: Independent of retained placenta, there is no difference in the maternal risks for hemorrhage, abruption, coagulopathy or infection between groups. Immaturity at delivery and monochorionicity are more common in pregnancies complicated by fetal demise. Neonatal morbidity and developmental outcome will be the focus of a longitudinal study comparing cotwin survivors to twins matched for chorionicity and gestational age at delivery.

Spontaneous Abortions in Couples Declining Multifetal Pregnancy Reduction

Multifetal pregnancy reduction (MFPR) has clearly improved the outcomes of multifetal gestations. Several recent reports have also suggested improved outcomes in nonreduced cases, but there have been methodologic concerns about the denominators, i.e. have all cases been included and is there a ‘hidden mortality’ of unknown lost cases. Here we assessed the outcome of patients telephoning to discuss MFPR, but who chose not to have the procedure. Over a 3-year period, 446 patients had MFPR by one operator. Nineteen patients chose not to have the procedure. There were 11 preterm births, 1 term delivery, and 5 spontaneous losses (7 of 17) prior to 24 weeks, a loss rate of 35%. Two patients delivering triplets had a loss of 1 fetus/neonate. These data suggest that the loss rates of nonreduced pregnancies may be higher than generally thought, making the improvements with MFPR even bigger than generally realized.

Principles of screening.

Over the past several decades, the principles by which screening tests are performed have slowly been developed and refined. The key distinction for the clinician to understand is the difference between diagnostic tests, which give a definitive answer, and screening tests, which identify who among the low-risk population is at high risk.

Demographic Factors for Utilization of Invasive Genetic Testing after Multifetal Pregnancy Reduction

Objective: Pregnant infertility patients are commonly old enough to be offered prenatal diagnosis. However, they may be reluctant to undergo an additional invasive procedure. We, therefore, sought to determine what demographic factors, including race and ethnic group, influenced patients’ decisions to undergo genetic testing in addition to multifetal pregnancy reduction (MFPR). Methods: We retrospectively reviewed MFPR patients from July 1997 to June 1999 at our institution. Invasive genetic testing was routinely discussed. Maternal age, race, ethnicity, religion, egg source for in vitro fertilization (IVF) patients, and the remaining fetuses following MFPR were analyzed for invasive genetic testing determinants and were compared to our experiences with genetic referents to us for singleton pregnancies. 132 consecutive patients, of whom 49 were ≧35 years, including 15 having IVF with donor eggs, were included. Results: Maternal age was the single most significant determinant of testing. In donor egg cases, donor age was significant. Ethnic background, previous children, and the remaining number of fetuses after MFPR were also significant determinants. Conclusion: MFPR patients share similar demographics to the advanced maternal age population. Despite the very stressful situations, our data suggest that maternal age, and therefore genetic risk, is the most important determinant of choosing whether or not to have testing. However, patients’ decisions are, to varying degrees, modified by religious and ethnic considerations.

Multifetal Pregnancies: Evolution of Methods of Initiation and Impact of REI Certification for Patients Seeking Reduction

Objective: Multifetal pregnancy as a result of ovulation induction (OI) and assisted reproductive technologies (ART) correlate with Board certification in reproductive endocrinology and infertility (REI). Design: Retrospective chart analysis of 304 patients referred to Wayne State University (WSU) and Thomas Jefferson University (TJU) for multifetal pregnancy reduction (MFPR) from March 1986 to January 1995 compared to 275 patients referred from January 1 to December 31, 2000 at MCP Hahnemann University. Material and Methods: Chart review for fetal number, pregnancy generation (OI or ART) and physician REI Board certification from the American Board of Specialties Obstetrics and Gynecology. Information was available on 296 of 304 patients studied in the 1986–1995 WSU cohort and 275 patients studied from the MCP Hahnemann 2000 cohort. Results: Analysis of 296 multifetal pregnancies at WSU and TJU for REI Board status showed non-REI Board-certified (NREI) physicians generated 174 pregnancies with quadruplets or more compared to 122 quadruplets or more by REI Board-certified physicians. Board certification did not impact quadruplet or more rates for OI or ART (p < 0.368). Of 275 patients with triplets or more at MCP Hahnemann, 156 (56.7%) were from ARTs versus 41.2% from 1986–1995 (χ2 = 13.1, p < 0.001). Quintuplets or more decreased from 18.5 to 9.7% (χ2 = 8.3, p = 0.004), and for REIs from 22.1 to 9.6% (χ2 = 4.7, p < 0.01), while 14.4% of cases coming from non-REIs had quintuplets versus 9.6% from REIs (p = NS). Conclusions: Cases of MFPR from ARTs have risen, while percentage of cases with quintuplets have fallen in half. We found no difference in quintuplets between REIs and non-REIs overall, but REI quintuplets fell significantly, and NREI has not.

SECOND-TRIMESTER BIOCHEMICAL SCREENING

The past years have seen considerable progress in the area of biochemical screening. Increasing data have now clearly shown the advantages of multiple markers, particularly beta-hCG over AFP alone. There continues to be considerable controversy over the best mathematic algorithm and which markers are best (e.g., beta-HCG, uE3, and so forth). There seems to be a plateau of detection frequencies at about 65% to 70% with current methodologies. Further work needs to be done, however, including some new approaches, if there is to be substantial improvement of screening sensitivity. The combination of biochemical with biophysical parameters as discussed elsewhere in this issue represents the next level of sophistication in the attempt to identify the highest proportion of abnormalities with the fewest false-positives.

Sonographic Nuchal Markers for Down Syndrome Are More Common but Less Ominous in Gestations with a Male Fetus

Objective: A change in the normal male-to-female ratio has been reported in some autosomal trisomies (i.e., trisomy 21 or trisomy 18). The objective of the present study was to evaluate the male-to-female ratio in pregnancies with sonographic nuchal markers for Down syndrome. Methods: The results of amniocenteses performed for isolated nuchal markers for Down syndrome were grouped by fetal sex and by maternal age. The male-to-female ratio in normal and trisomic gestations was compared. Results: 584 fetal karyotypes were available for analysis. A significantly higher male-to-female ratio was observed. More affected gestations were observed in association with a female fetus. These differences were mainly attributed to the group of patients younger than 35 years that represents more than 80% of our study population. No difference was observed in pregnancies of patients older than 35 years of age. Conclusions: In patients younger than 35 years, sonographic nuchal markers for Down syndrome are more frequent (but apparently less ominous) in gestations with a male fetus. If the gender is known, counseling can be modified to include such differential risks.