COPENHAGEN — The chances of having a healthy newborn are similar among patients with a history of recurrent miscarriage, regardless of whether they have chromosomal abnormalities, Maureen T.M. Franssen, M.D., reported during the annual meeting of the European Society of Human Reproduction and Embryology.
But carriers of chromosomal abnormalities have a higher risk of repeat miscarriage before eventually achieving their successful pregnancies.
Dr. Franssen of the Center for Reproductive Medicine, Academic Medical Center, Amsterdam, and her associates analyzed 705 couples who had experienced recurrent miscarriage and had been tested for chromosome abnormalities.
A total of 278 couples were identified as carriers, meaning that they had chromosome abnormalities. In carrier couples, products of conception can sometimes have an unbalanced karyotype, resulting in miscarriage, stillbirth, or the birth of a child with major congenital handicaps, she explained.
The study compared the reproductive outcomes of carrier couples with those of the 427 noncarrier couples (controls) over a mean follow-up period of 5.8 years.
A significantly greater percentage of the carrier couples than controls (16% vs. 6%) decided to stop trying to get pregnant. The main reason given by carriers was their risk of giving birth to a viable but unhealthy child. Among controls, the main reason was advanced maternal age.
Both groups had similar rates of successful reproductive outcomes, meaning the birth of a healthy child (83% for carriers and 84% for controls), but the carrier group had a significantly higher rate of miscarriage before a successful pregnancy (49% vs. 30%).
Both groups had similar rates of ectopic pregnancy, stillbirth, and neonatal death. In the carrier group these adverse outcomes were sometimes, but not always, the result of chromosomal abnormalities.
Both groups also had similar rates of pregnancy termination (2%), and in carrier couples two pregnancies were terminated because of an unbalanced structural chromosome abnormality.
Finally, in the 550 pregnancies in the carrier group two children (0.2%) with an unbalanced structural chromosome abnormality and major congenital abnormalities were born. One of these children died immediately after birth.
“In carrier couples … the risk of viable unbalanced offspring is very low,” Dr. Franssen said. “These couples have a good prognosis toward successful reproductive outcome, which is similar to noncarrier couples, even though their risk of miscarriage is higher.”
But a North American expert in miscarriage said she is concerned that the researchers grouped together all carriers without identifying the causes of miscarriage in each couple.
“We need to address each couple individually because there are couples whose specific chromosome abnormalities increase the likelihood of their pregnancy being unbalanced. But there are also many couples [with chromosome abnormalities] who are having miscarriages for other reasons,” she said during an interview.
In a study that she presented last year at the American Society for Reproductive Medicine's annual meeting, Dr. Stephenson showed that among carrier couples, only one-third of miscarriages are due to fetal chromosomal abnormalities, while two-thirds are not. To counsel recurrent miscarriage patients using only parental chromosome analysis without analyzing their products of conception is to disregard a big piece of the puzzle, she said.
For example, in the subgroup of carrier couples whose adverse reproductive outcomes are directly linked to their chromosome abnormalities, the chances of a successful outcome are much lower than in the group as a whole.
“The important part is to send the miscarriage specimen for cytogenetic analysis to try to get as much information as to why the miscarriage occurred. Then we can counsel the couple appropriately,” Dr. Stephenson said.