Slightly fewer than 4 million babies are born in the United States each year, and the details of how, when, and where they arrive are always shifting. Total fertility rate is an estimate of the average number of births a group of women have over their lifetime. The U.S. fertility rate has been declining since 2007.

The latest news is that the fertility rate in the United States is still waning – down 1 percent in 2013 from 2012. The number of births is still slightly down too. The latest birth count (3,932,181) is 9 percent less than the all-time high of 4,316,233 births in 2007.

While the United States remains the third most populous country in the world (after China and India), it's projected to drop to fourth (after Nigeria) by 2050. Many say the tumultuous economy has led to the drop in numbers. But long-term trends in marriage, economic development, and women’s education, employment, and access to contraception are responsible for the decline too.

Read on for more revealing facts about birth in the United States.

The big day

The most popular day

The most popular day for babies to make their entrance in 2013 was Tuesday, followed by Thursday.

The least popular day

Sunday was the slowest day, with 33.3 fewer births than average. Scheduled c-sections and induced labors have a big influence on the reason why far fewer babies are born on the weekend, but spontaneous (unscheduled) deliveries occur less often on the weekend too.

The biggest month

In 2013 more newborns arrived in August than in any other month. The second, third, and fourth most popular birthday months were July, October, and September, in that order.

Birth numbers and rates in the states

The number of births went down for 12 states, rose in 3 states, and remained about the same for the rest of the states and the District of Columbia in 2013. Birth rates ranged from 50.8 births per 1,000 women age 15 to 44 in New Hampshire to 80.9 per 1,000 in Utah.

States with the most births

California, Texas, and New York (in descending order) had the greatest number of births.

States with the highest birth rate

Utah had the highest birth rate, with 80.9 births per 1,000 women age 15 to 44. Alaska, Hawaii, Idaho, Nebraska, North Dakota, Oklahoma, South Dakota, and Texas, had more than 70 births per 1,000 women.

States with the fewest births

Vermont had the fewest births, followed by Wyoming, the District of Columbia, and North Dakota.

States with the lowest birth rate

New Hampshire had the lowest birth rate, with 50.8 births per 1,000 women age 15 to 44. Connecticut, Florida, Maine, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont, and the District of Columbia had fewer than 60 births per 1,000 women.

The age and fertility of moms

Age of first-time moms

Over the last three decades, women have been waiting longer to have children. In 1970 the average age of a first-time mother was 21.4. In 2013 the average age was 26. How old were you when you had your first child?

Birth rate

In 2013 the birth rate in the United States was 62.5 births per 1,000 women age 15 to 44. This was a 1 percent decline from 2012, reaching another record low.

Number of births by age

Here's how the numbers played out among U.S. women in 2013 compared to 2012.

Age 15 to 19: The number of births fell 11 percent.

Age 20 to 24: The number of births fell 2 percent.

Age 25 to 29: The number of births declined slightly (less than 1 percent).

Age 30 to 34: The number of births increased 2 percent.

Age 35 to 39: The number of births increased 2 percent.

Age 40 to 44: The number of births was essentially unchanged.

Age 45 and over: The number of births increased 14 percent.

The marital status of moms

In 2014 in the United States, 9,929,000 single moms were living with kids younger than 18, up from 3.4 million in 1970.

The percentage of births to moms who weren't married has held steady since its peak of 41 percent in 2009. The percentage in 2013 was 40.6, slightly lower than in 2012 (40.7).

Younger teens in the 15 to 17 age group accounted for the steepest decline in nonmarital birth rates in 2013, falling 13 percent from 2012 and continuing a steady decline over the past several decades. The largest increase in births to unmarried women has been among those in their 30s.

The work status of pregnant and new moms

Stay-at-home moms in 2012: 10.4 million

First-time moms who worked during their pregnancy: 65.6 percent (and 56.1 percent of them worked full time) in 2008

Between 1961 and 1965, 44.4 percent of first-time moms worked while pregnant.

First-time moms who worked during the month before they gave birth: 64.6 percent in 2006 to 2008

Between 1961 and 1965, 34.6 percent of first-time moms worked during the last month of pregnancy.

First-time moms who worked six months after they gave birth: 57.4 percent in 2005 to 2007

In the early 1960s, the percentage of first-timers working six months after giving birth was 13.7 percent.

Prenatal health

Prenatal care

The percentage of women receiving prenatal care in the first trimester of pregnancy was 73.7 percent among the 36 states and District of Columbia that reported this information in 2011 – only 6 percent of pregnant women received prenatal care late in pregnancy or not at all.

Pregnancy weight gain

In a 30-state reporting area during 2009 and 2010, 31.8 percent of women gained the recommended amount of weight during their pregnancy, 47.8 percent gained an excessive amount of weight, and 20.5 percent didn't gain an adequate amount of weight.

Gestational weight gain recommendations vary based on a woman’s pre-pregnancy weight and height. Inadequate weight gain is associated with a higher risk of problems, such as low birth weight and preterm birth, while excessive weight gain is linked to problems including gestational diabetes, preeclampsia, c-sections, and weight retention after pregnancy.

How do you feel about the weight you gained during pregnancy?

Moms-to-be who smoke

In the 24 states that kept track of this information in 2011, 1 in 10 women reported smoking during the last three months of pregnancy. Those who did so were more likely to cause major health problems for their babies, including low birth weight, preterm birth, and certain birth defects than women who didn't smoke.

If you're trying to quit get tips on kicking the habit.

Birth and delivery

Doctors and hospitals

In 2013 most moms in the United States (98.6 percent) gave birth in a hospital with the help of a medical doctor (85.4 percent). Certified nurse midwives attended 7.8 percent of all births, up from less than 1 percent in the mid-1970s.

Midwives, birth centers, and home births

Most midwife-attended births are also in hospitals, but of the 1.4 percent of births that took place outside a hospital in 2013, 64.4 percent were in homes and 30.2 percent were in birth centers. The number of home births was the highest since this statistic began being reported in 1989.

Certified nurse midwives attended 48 percent of home births in 2013. Montana had the highest rate of home births at 2.5 percent, and six other states also had 2 percent or more.

Epidural use

Of the 27 states that kept track of epidural use in labor, 61 percent of mothers who delivered a single baby vaginally in 2008 received an epidural or spinal block.

C-sections

Cesarean deliveries held steady in 2013 by declining a fraction to 32.7 percent of births (compared with 32.8 percent for 2010-12). The c-section rate had climbed 60 percent in the United States from 1996 to 2009.

Induction and other techniques

The number of women who had labor induced has more than doubled since 1990. In 2013, 23 percent of labors were induced, compared with 22.8 percent in 2012.

However, the number of babies delivered with forceps or vacuum extraction continues to decline – 3.3 percent in 2013 down from 3.4 percent in 2012. In 1990 almost 1 in 10 babies was delivered with forceps or vacuum extraction, compared with about 1 in 30 in 2013.

Boys vs. girls

With about 1,049 male babies born for every 1,000 female babies born in 2013, boys are keeping the edge in a ratio that's stayed about the same over the past 60 years.

Twins

The number of twins born in the United States increased 2 percent in 2013 – to 33.7 sets of twins born for every 1,000 births. While this is the highest rate on record, the numbers have remained roughly the same since 2009 – after skyrocketing over 70 percent from 1980 to 2008.

Triplets and more

The rate of triplets and higher multiple births in 2013 was 119.5 per 100,000 births, a 4 percent decline from the 2012 rate. After shooting up by more than 400 percent between 1980 and 1998, the rate has dropped, especially since 2004. Average declines of more than 4 percent each year have been reported since then. In part, this is because of improvements in fertility treatments.

Big families

In 2013, 20,722 mothers gave birth for the eighth or more time.

Premature babies

The preterm birth rate declined in the United States for the seventh straight year to 11.39 percent of births in 2013. Between 1981 and 2006, the percentage of infants born preterm (less than 37 weeks) rose by more than one-third but has been on the decline since.

Weight at birth

The percentage of babies born in 2013 at low birth weight (less than 5 pounds, 8 ounces, or 2,500 grams) was 8.2 – basically unchanged from 2012 when it was 7.99.

Sources

Most of the numbers in this article come from data published by the U.S. Centers for Disease Control (CDC). These figures are sometimes compiled and analyzed over several years, which is why some of the most recent information is from 2013.

World population figures come from the Population Reference Bureau’s “2014 World Population Data Sheet.”

We also pulled a few interesting statistics from the U.S. Census Bureau report, "Maternity Leave and Employment Patterns of First-Time Mothers: 1961-2008," along with a few other sources.

Find out more

For more CDC birth data, visit the agency's Births: Final Data for 2013.