As fertility rates fall nationwide, Connecticut continues to rank among the lowest in the country—a trend doctors attribute to women here delaying childbearing. In 2016, the most recent year for which state-level data is available, Connecticut had 53.4 births per 1,000 women ages 15 to 44, compared with a national average of 62 per 1,000 women, according to data from the Centers for Disease Control and Prevention (CDC). Just four states had lower rates than Connecticut in 2016, and all are in New England: Vermont at 50.3 births per 1,000 women, New Hampshire at 50.9, Rhode Island at 51.8 and Massachusetts at 51.9. The states with the highest fertility rates in 2016 were South Dakota at 77.7, North Dakota at 77.3, Utah at 76.2 and Alaska at 76.1, the CDC reports. Unlike birth rates, which take an entire population into account, fertility rates reflect the share of babies born to women of childbearing age. Connecticut typically ranks low on the list, along with other “high achievement, high education states,” said Dr. Harold J. Sauer, chairman of obstetrics and gynecology at Yale New Haven Health’s Bridgeport Hospital.