(CNN) Three new reports from the US Centers for Disease Control and Prevention bring both good and bad news about Americans' health.

Death rates for heart disease, cancer and HIV are all down in the United States in the year ending mid-2017 compared to the same period last year,according to one report published Friday by the CDC's National Center for Health Statistics. Despite these "wins," the overall mortality rate has increased from the same time last year, the report also indicated. This overall uptick includes the death rate for drug overdoses.

The rate of overdose deaths has "increased greatly from last year," said Farida Ahmad, the report's author and mortality surveillance lead at the center.

"Heart disease and cancer are traditionally the major causes of death," she said, so the overall death rate has followed the same trend in the past.

"What we're seeing here is even though heart disease is going down, even though cancer is going down, the overall death rate is going up," Ahmad said. Why? People apparently are dying of "other causes," she said, and though drug overdoses contribute to the rising rate, they are only partly responsible for the increase.

Two other reports released Friday by the National Center for Health Statistics look at infant mortality and factors related to birth . These reports show that teen pregnancy continues to decline. Meanwhile, overall preterm births have persistently increased over the past couple of years.

"Preterm birth is associated with a number of adverse outcomes for the infant and for the mom, and so seeing that trend kind of ticking in the wrong direction is something that could be potentially concerning," said Lauren Rossen, report author and reproductive health surveillance lead at the National Center for Health Statistics.

Preterm birth is one of the biggest risk factors for infant mortality, she said.

How and why the reports are made

All three reports are based on "provisional" data, or incomplete information from the states.

For example, if the states have submitted most but not all of the necessary data, the statisticians will estimate a provisional number based on prior history or what's happening across the states or by upweighting or increasing the proportion of the data, Rossen said: "We try to mitigate the impact of missing data."

Ahmad said the center has been producing annual reports about mortality every year, but the process can take up to two years due to the long wait for official data from each state.

"But as our databases and systems have improved, we have been striving to put out data in a more timely way so that it's more accessible," she said. Improvements made by both state and federal governments mean the center can now look at data in "what we call real-time."

Though not exactly "real time" by everyday standards, Friday's reports include estimates up to the second quarter of 2017.

"We want to get a picture while it's relevant," Ahmad said, adding that the provisional data are subject to change once the final numbers come in.

Infant mortality

Rossen's two reports presented estimates for infant mortality. Deaths in babies younger than 1 year old are recorded as a number per 1,000 live births.

The infant mortality rate is made up of two subcategories: the neonatal mortality rate (deaths of infants up to 27 days old per 1,000 live births) and postneonatal mortality rate (deaths of infants ages 28 days through 11 months per 1,000 live births).

For 2016, the rate of infant mortality was 5.87 per 1,000 births. Neonatal mortality was 3.88 per 1,000 births and postneonatal mortality was 2 per 1,000 births.

"The majority of infant mortality occurs during that early (neonatal) period," Rossen said. Common causes include congenital deformities and genetic mutations, disorders related to low birth weight, and maternal complications.

The causes of postneonatal deaths tend to be sudden unexpected infant death (SUID), which includes sudden infant death syndrome (SIDS), unknown cause, and accidental suffocation and strangulation in bed, she said.

Rossen's reports also included data for age-specific birth rates and preterm birth rates.

"We see age-specific birth rates declining among the younger groups," those under the age of 30, she said. Meanwhile, birth rates are increasing among older moms. The CDC has seen this pattern for several years, she said.

Adult deaths

Ahmad's report estimated the rates of death from each of the 15 leading causes of death . Additionally, she and her co-author estimated deaths due to drug overdoses, falls for people 65 and older, firearm-related deaths, HIV (human immunodeficiency virus) disease and homicide.

"Firearm-related deaths are up," she said, as are falls for people over 65. However, drug overdose deaths show "the most stark increase."

Because overdose deaths require more investigation, the provisional data are available through only the final quarter of 2016 instead of the second quarter 2017, which is the case for the other causes of death.

In the fourth quarter of 2015, drug overdoses caused the death of 16.3 people for every 100,000 Americans, the report says. In fourth-quarter 2016, they increased to 19.8 for every 100,000 people.

"Compared to the changes in other causes of death, that's pretty significant," Ahmad said.

By identifying emerging trends, the new reports can help health care professionals find the best strategies for helping people, Ahmad said.

Dr. David Friedman, chief of heart failure services at Northwell Health's Long Island Jewish Valley Stream Hospital in New York, is one such professional.

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With a lower number for the heart disease death rate, Friedman suggested they might be a result of widely adopted "good cardiovascular treatments" and better access to health care.

"Additionally, improving diets and exercise lifestyle choices are more widely prescribed and in the public eye," said Friedman, who was not involved in the new reports.

Each report also helps the National Center for Health Statistics itself identify mortality trends that could probably use "a little more scrutiny," Rossen said. "Why that's happening, what factors are related to that, and what are the consequences?"