CORONADO, CALIF. –
In addition, multiples conceived using ART – including twins – continue to be the biggest preventable risk factor for adverse pregnancy and fetal outcomes.
Those are key points that, made during a wide-ranging talk about the adverse pregnancy and fetal outcomes related to ART at a meeting on in vitro fertilization (IVF) and embryo transfer sponsored by the University of California, San Diego.
In 2016, Barbara Luke, ScD, MPH, and her colleagues published results from the ongoing Massachusetts Outcomes Study of Reproductive Technologies (). They found that pregnancy plurality is the predominant risk factor for infants and mothers. Of 8,948 birth outcomes resulting from ART, risks for pregnancy-induced hypertension, cesarean delivery, gestational diabetes, preterm birth, birth defects, and small for gestational age were significantly increased among twins.
“Lowering the plurality rate, including twins, should substantially reduce morbidity with ART,” said Dr. Gambone, professor emeritus at the David Geffen School of Medicine at the University of California, Los Angeles, who was not affiliated with the study. Thawed embryos were associated with a higher risk for pregnancy-induced hypertension and large for gestational age offspring, but a lower risk for low birth weight and small for gestational age.
According to, elective singleton embryo transfer increased from 35% of all cycles in 2015 to 42% in 2016, while singleton births increased from 80.5% to 84% during the same time period. In addition, the proportion of twins born in 2015 was 19% and declined to 16% in 2016, while the percentage of triplets or greater born was the same in both years (0.4%).
Meanwhile, in an analysis of more than 1.1 million cycles between 2000 and 2011 drawn from Centers for Disease Control and Prevention surveillance data, researchers found that the most commonly reported patient complication was ovarian hyperstimulation syndrome (a peak of 154 per 10,000 autologous cycles) and hospitalization (a peak of 35 per 10,000 autologous cycles;
Today, the most feared maternal and pregnancy outcome from ART is breast and ovarian cancer from treatment, he said, while the most feared outcome in offspring is birth defects from treatment. On the breast cancer front, an analysis of nearly 2 million women provided some reassurance ( ). It found no increased risk of breast cancer in women who have birth after ART, compared with women who gave birth after spontaneous conception (adjusted hazard ratio, 0.84). It also found no increased risk in women who received ovarian stimulation or other hormonal treatment for infertility (HRs, 0.86 and 0.79, respectively). A smaller study with a median follow-up of 21 years found no difference in the rate of invasive and in situ breast cancer between women who received IVF treatment and those who did not ( ). However, a recent analysis from Great Britain found a slight increase for in situ breast cancer that was associated with women who had a higher number of treatment cycles ( ).
On the ovarian cancer front, a case-control analysis of 1,900 women conducted by researchers at Mayo Clinic found that infertile women who used fertility drugs were not at increased risk of developing ovarian tumors, compared with infertile women who did not use fertility drugs (adjusted odds ratio, 0.64;). There also was no increased risk because of underlying infertility or any increase in borderline tumors. More recently, presented at the annual meeting of the European Society of Human Reproduction and Embryology, based on a large cohort study from Denmark, found a slightly higher overall risk of ovarian cancer among the ART women (0.11%), compared with non-ART controls (0.06%). However, the analysis also showed comparably higher rates of ovarian cancer in women who were nulliparous (a risk factor for ovarian cancer) and in the ART women who had a female cause of infertility. In an analysis from Great Britain, increased ovarian tumor risk was limited to women with endometriosis, low parity, or both ( ). Dr. Gambone noted that published online Oct. 23, 2017 in Nature Communication implicates the fallopian tube, rather than the ovaries, as a probable source of papillary serous cancers.
Women who are subfertile should be counseled about the increased risk of birth defects, irrespective of whether they undergo IVF or not, said Dr. Gambone, who also runs a private infertility practice in Durango, Colo. Studies consistently show an increased risk associated with subfertility. A large, retrospective cohort analysis of live and stillbirths from 2004 to 2010 in Massachusetts found that congenital anomalies were reported in 2% of ART births, 1.7% of subfertile births, and 1.4% of fertile births (). The adjusted prevalence ratios for birth defects were 1.5 for ART births and 1.3 for subfertile births, compared with fertile mother births. The researchers observed elevated rates of several birth defects with ART, including tetralogy of Fallot and hypospadias. Subfertility and multiple births affect these associations, with multiple births explaining 36% of the relative effect of ART on nonchromosomal birth defects.
“The absolute risk of birth defects is small with ART,” Dr. Gambone said. “A significant portion [but not all] is related to multiple births and underlying subfertility.” A more recent analysis found that subfertile women were 21% more likely to have babies born with birth defects, compared with fertile women ().
In a study of the overall risk and etiology of major birth defects, researchers from Utah determined that they affect 1 in 33 babies in the United States at an annual direct cost of $2.6 billion per year (). Although major birth defects are the leading cause of infant mortality (20%), a known cause of the defect was established in only 20.2% of cases. “Of that percentage, the majority are chromosome or genetic causes,” Dr. Gambone said. “Interestingly, ART and/or subfertility were not listed in this analysis as causes of birth defects. However, the authors speculated that as genetic technology improves, both genetic and epigenetic causes will be identified.”
Dr. Gambone reported no relevant financial disclosures.