Questions for Joyce Martin, Lead Author of, “Is Twin Childbearing on the Decline? Twin births in the United States, 2014-2018.”
Q: Is this the first time you have published a report on this topic?
JM: General information on twin births is published annually in the National Vital Statistics Report series “Births: Final Data.” A number of special reports have also been published on the topic in the past.
Q: Why did you decide to do a report on trends in twin births?
JM: There appears to be a reversal in the direction of trends in twin childbearing in the US. After increasing for decades, the number and rate of twin births trended downward for 2014-2018. This is important to public health because of the greater risk of poor pregnancy outcome, such as preterm birth and infant death, for babies born in twin pregnancies compared with those born in single pregnancies.
Q: How did the data vary by maternal age, race and Hispanic origin and state of residence?
JM: Trends differed by all of these characteristics. Rates for women in their 30s and over declined by 10%-12% and rates for women 40 and over by more than 20%. In contrast, there was no significant change in trends for women in their twenties. Among the three race/Hispanic origin groups studied, twin childbearing declined for 2014-2018 among non-Hispanic white women but were essentially unchanged among non-Hispanic black and Hispanic women. Rates declined significantly in 17 states and increased in only three states.
Q: Was there a specific finding in your report that surprised you?
JM: The steady decline in twinning from 2014 through 2018 after many years of increases was surprising as was the fairly large declines among women aged 30 and over.
Q: Do you foresee the decline in twins continuing?
JM: As fertility procedures continue to improve, twin births, and especially higher-order multiple births, would be expected to continue to decline. However, it is important to note that older mothers, those aged 35 and over, are more likely to have a twin delivery without the use of fertility therapies. The older age of women at birth may also affect twining rates.