Master Class

Investigating the etiology of recurrent pregnancy loss

With attention to the timing of loss


Introduction: Reassurance through pregnancy loss and workups

Pregnancy loss is not an uncommon complication but it can be associated with significant stress among parents and loved ones when it occurs. Especially when recurrent, it also becomes a medical dilemma for physicians and nurses because the cause is not always obvious immediately, and even with exploration, the cause may not always be found.

First and foremost, it is important that physicians provide counseling and reassurance to families experiencing loss, and that they encourage a level of patience while the investigation for loss is done. Investigations tend not to be linear. One must look at a number of diagnostic areas including genetics, anatomy, immunology, and infections.

Dr. E. Albert Reece, a maternal-fetal medicine specialist, University of Maryland School of Medicine

Dr. E. Albert Reece

Even with an extensive workup, what often is found are potential associations rather than precise causes. For instance, one may find that certain antibodies or certain conditions are present, or that certain anatomic structures are abnormal. While such findings are not necessarily causative, there are therapeutic interventions that we can offer to address many of the conditions (e.g., surgical correction of the septate uterus, and low-dose aspirin and heparin for antiphospholipid syndrome).

Less than 1% of couples experience recurrent pregnancy loss (traditionally defined as three or more losses), so parents who experience one loss should be given reassurance that their loss was likely a sporadic miscarriage and that chances of recurrence will be low. Even as workups proceed, reassurance is important.

For this month’s Master Class in Obstetrics we’ve invited Wendy L. Kinzler, MD, and Anthony Vintzileos, MD, both of whom have expertise in the area of recurrent pregnancy loss, to review the potential causes and the management approach. They focus on the first trimester, when genetic causes predominate, and the early second trimester, when undetected uterine factors can be at play. They explain that the gestational age at which recurrent losses occur is an important factor in decoding etiology and management.

Dr. Kinzler is associate dean, graduate medical education, and professor of obstetrics and gynecology at NYU Long Island School of Medicine, Mineola, N.Y., and Dr. Vintzileos is chief patient safety officer for obstetrics, Northwell Health–Western Region, and professor in the department of obstetrics and gynecology in the Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, N.Y. Dr. Kinzler and Dr. Vintzileos reported no relevant disclosures.

E. Albert Reece, MD, PhD, MBA, a maternal-fetal medicine specialist, is dean emeritus of the University of Maryland School of Medicine, former university executive vice president; currently the endowed professor and director of the Center for Advanced Research Training and Innovation (CARTI), and senior scientist in the Center for Birth Defects Research. Dr. Reece reported no relevant disclosures. He is the medical editor of this column. Contact him at

Investigating the etiology of recurrent pregnancy loss

Pregnancy loss is defined as a loss occurring at < 20 weeks’ gestation. Any pregnancy loss is a devastating experience and couples deserve a thoughtful approach to identifying possible causes and/or predisposing factors.

Consideration of the timing of the pregnancy loss can provide a useful guide to this evaluation, as etiologies vary depending on when in gestation losses occur. In this Master Class, we will address the evaluation of pregnancy loss at < 20 weeks’ gestation, with particular attention to first trimester and early second trimester causes. Literature on the role of the cervix and intra-amniotic infection in midtrimester loss is extensive and will not be covered here.

Stepwise approach to evaluation of recurrent pregnancy loss

Although early first trimester miscarriage is common, occurring in approximately 15% of clinically recognized pregnancies, only 2%-3% of couples experience two or more miscarriages and 0.5%-1% experience three or more.

When to begin a diagnostic workup should be part of a shared decision-making process, taking into consideration future family planning, parity, number of previous losses, and notably, the gestational age at which loss(es) occurred. Recurrence rates for first trimester miscarriage are similar after two versus three consecutive losses and either situation usually prompts an evaluation, whereas any second-trimester loss should be evaluated.

Increasingly, we are appreciating the value of a more targeted, gestational age–driven approach to the evaluation of pregnancy loss in an attempt to provide grieving parents with useful information without subjecting them to a wide array of expensive and unnecessary tests.

Genetic causes

The earlier the pregnancy loss, the more likely it is the result of abnormal fetal genetics. Genetic factors should be considered as the most likely cause for first trimester pregnancy losses (especially those occurring at < 10 weeks’ gestation), the most frequent being autosomal trisomies or monosomy X. The vast majority of trisomy conceptuses are sporadic in nature and are related to the natural aging process of the ovary (increasing the rate of meiotic nondisjunction).

Dr. Wendy L. Kinzler, professor of obstetrics and gynecology at NYU Long Island School of Medicine, Mineola, NY NYU Long Island School of Medicine

Dr. Wendy L. Kinzler

If fetal aneuploidy is identified in a pregnancy loss, couples can be counseled about the definitive cause of the loss and can be counseled about recurrence based on age-related risks and/or tests of ovarian reserve. Recurrent pregnancy loss (RPL) is only rarely associated with a parental translocation (< 5%). Testing parental karyotypes should be reserved for cases in which the fetal karyotypes are unknown or in which an unbalanced translocation was identified in the fetus.

When a first trimester pregnancy loss is diagnosed, chorionic villus sampling (CVS) with microarray testing is the most reliable and comprehensive method for evaluating potential genetic causes. It provides valuable information even when cells are not viable and reduces the risk of maternal cell contamination – two significant limitations to standard karyotype analysis performed on tissue passed spontaneously or at the time of D&C. Studies of products of conception (POC) testing with microarray have documented the detection of abnormalities in an additional 10%-15% of cases compared with traditional karyotype analysis.

Dr. Anthony Vintzileos, professor of obstetrics and gynecology at the Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, N.Y. Hofstra/Northwell

Dr. Anthony Vintzileos

When CVS is not feasible, testing maternal serum for cell-free DNA is a reasonable alternative. In a prospective cohort study of 50 maternal blood samples taken after fetal demise, 76% of samples yielded cell-free DNA results, meaning fetal fractions were within the detectable range. The higher the gestational age at the time of loss, the higher the chance of obtaining a result: Findings in the study were possible in 88% of samples when the gestational age was 8 weeks or greater, and in 53% of cases involving a lower gestational age. The time from demise to blood draw did not affect the likelihood of obtaining a result (Obstet Gynecol. 2015 Jun;125[6]:1321-29).

When neither CVS nor cell-free DNA analysis is feasible, analysis of either spontaneously passed tissue or tissue obtained at the time of a D&C may still be worthwhile. Maternal cell contamination, of course, is the main downside.

A paper published in 2020 documented the value of refocusing the initial workup. Researchers reported that 57% of 1,400 cases of recurrent pregnancy loss went unexplained using the 2012 ASRM guidelines, which included parental karyotyping but not POC cytogenetic analysis. When parental karyotypes were omitted from the initial workup and POC analysis with 24-chromosome microarray was added, at least one potential explanation for loss could be identified in 92% of cases. Only 8% were left “unexplained” (Curr Opin Obstet Gynecol. 2020 Oct;32[5]:371-9).


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