Premature birth is also known as preterm birth. It is defined as a baby born alive before reaching the gestational age (term to describe the length of pregnancy) of 37 weeks. The typical gestational period is usually 40 weeks which is considered a full-term pregnancy.
Premature births occur in about 5-18% of all pregnancies and affect approximately 15 million children each year. Moreover, complications of premature births are the leading cause of death globally for children under age 5 accounting for 1 million deaths in 2015.
Most (~80%) premature births are considered spontaneous, as opposed to medically indicated. About half are due to the onset of preterm labor with most of the rest being due to premature rupture of membranes (PROM).
Medically indicated (or iatrogenic) preterm birth refers to pregnancies that end early due to issues that affect the health of the mother or the fetus, such as:
- placenta previa
- abruption placentae
- fetal growth restriction
- multiple gestations
Premature births are categorized based on the length of completed gestation. There is some variation in the categories depending on the reporting organization, as noted below:
- Moderate to late preterm: between 32 to <37 weeks
- Very preterm: 28-<32 weeks
- Extremely preterm: <28 weeks
- Preterm: <37 weeks
- Late Preterm: 34-36 weeks
- Early preterm: <34 weeks
- Late preterm: between 34 and 36 completed weeks of gestation
- Moderately preterm: between 32 and 34 weeks
- Very preterm, born at less than 32 weeks
- Extremely preterm, born at or before 25 weeks
Most premature births occur in the late preterm stage. A birth of <20 weeks is called a miscarriage, pregnancy loss, or spontaneous abortion in the United States.
Related Content: What You Need To Know About Recurrent Pregnancy Loss
This article explores the causes, treatments, and prevention of premature births. It also looks at the short and long-term impacts of prematurity on newborns. Finally, we discuss how the COVID-19 pandemic impacts the condition.
What are the risk factors for premature birth?
More than 80% of preterm births are due to unknown causes. Of the remaining 20%, half are idiopathic (unknown), 30% are due to premature rupture of the mother’s water, which is also known as Premature Rupture of Membranes (PROM). The rest are due to maternal medical complications.
Living in economically disadvantaged areas, having poor living conditions, and limited access to health care, (all considered social determinants of health (SDOH) are amongst the conditions that play a role in worsening the rates of preterm delivery as well.
Among the more common risk factors for preterm birth are the following.
According to CDC research, preterm births are more common among the youngest (younger than 17) and oldest mothers (older than 35). While rates of premature birth in the US declined between 2007-2014 partly due to fewer births among teens and younger women, the preterm birth rate rose for the fifth year in a row in 2019.
Short interpregnancy interval
An interval of fewer than 6 months between pregnancies triples the risk for spontaneous preterm birth at less than 34 weeks. Because of this, the March of Dimes recommends that women space their pregnancies at least 18 months apart.
According to The World Health Organization, half of the babies born at or below 32 weeks (2 months early) in low-income settings die due to a lack of feasible, cost-effective care, such as warmth, breastfeeding support, and basic care for infections and breathing difficulties. This highlights the important role that socioeconomic factors play in premature birth and associated deaths.
Black women have higher rates of preterm birth than white women. It is believed this is related to both genetic and environmental factors (such as socioeconomic status, lack of medical care, and other SDOH factors).
The widespread availability of assisted reproductive technology (ART) has been associated with a significant increase in multiple gestations. Although they account for a small percentage of births overall, they account for almost a quarter of births before 32 weeks. Prevention and reduction of multifetal gestations via recent advances in ART has moderated this cause of premature birth in recent years.
Chronic medical conditions
Chronic medical conditions, such as diabetes, hypertension, heart and kidney disease, and depression increase the risk for both spontaneous and medically indicated preterm births. Whenever possible, it is recommended that women with these conditions optimize the management of them prior to becoming pregnant.
Extremes of weight
Obesity increases the risk of medically indicated PTB as well as PROM. There is some evidence that maternal undernutrition may increase it as well. Certainly, maternal deficiencies of certain vitamins and other essential elements place the fetus at risk for congenital disorders.
Maternal substance use increases the risk of PTB. This includes smoking, drinking alcohol, and use of drugs of abuse, such as cocaine or opioids. Of note, women who use cocaine or are polysubstance abusers have a high rate of early (<32 weeks)preterm birth.
Silent urinary tract infections (known as asymptomatic bacteriuria) are an independent risk factor for PTB. It is recommended that pregnant women have a first-trimester urine culture performed and be treated with antibiotics if positive. However, a recent Cochrane review states that this recommendation is based on “low level” evidence. Although periodontal disease has a reported association with preterm birth, so far there is no compelling evidence that treatment improved pregnancy outcome.
A history of having had a prior spontaneous preterm birth (sPTB) is a major risk factor for recurrence. This includes women without a term pregnancy after an sPTB and women with a history of multiple sPTBs. Women with a prior medically indicated preterm birth are at risk for both recurrent and spontaneous preterm births.
Women who have had prior cervical surgery for treatment of localized cervical cancer may be at risk for late premature births due to cervical insufficiency. It is recommended that women with this history be screened with transvaginal ultrasound at about 18-24 weeks of gestation in order to determine the cervical length.
When it comes to factors out of women’s control that increase the risk of preterm labor, such as how weak or short their cervix is, or if they have an abnormal uterus, they may be treated in the following ways to help reduce the chance of a preterm delivery:
- Progesterone therapy, which can be given as a shot or inserted into the vagina to help reduce the chances of going into labor early.
- Close monitoring of cervical length, and cerclages, which is a procedure that stitches the woman’s cervix shut, has helped reduce the chances of preterm deliveries. A cerclage is usually recommended by a doctor when the woman has already had a preemie, miscarriage, or has a smaller cervix.
Prevention of premature births
While the cause of most preterm births is unknown, there are life decisions that play a role in helping prevent early labor before and during pregnancy.
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Chronic condition recommendations
If mothers have any of the chronic conditions listed above or suffer from a different one, they should speak to their doctor about how it can potentially impact their pregnancy.
They need to learn if there are any changes that need to be made to medications or other treatment they may be receiving. For example, women with diabetes will want to optimize blood sugar control and overweight/obese type two diabetics should be encouraged to lose weight. Women on chronic medications should review all of them for safety during pregnancy. This includes any over-the-counter medications or supplements that they might be taking.
- The doctor might have the following recommendations to reduce the risk and/or complications related to premature birth, including:
- Although bed rest, at home or in the hospital, is sometimes recommended, there is no evidence to show that it is effective in treating preterm labor or preventing preterm birth
- Your doctor may prescribe antibiotics if PPROM occurs. This may prevent you and your baby from getting a serious infection.
- According to a 2017 study, progesterone therapy is applicable to only a small percentage of pregnant women (primarily those with a shortened cervix and those with a history of previous preterm birth). The benefits to the general population appear to be limited. However, several studies have shown that conducting population-based cervical screening programs combined with progesterone therapy is promising.
- Steroids prior to delivery have helped decrease some of the long-term complications of prematurity. Steroids can help the baby’s lungs grow faster in the womb so they will be less likely to have breathing trouble on their own once they are born.
- A meta-analysis of randomized controlled trials published in the American Journal of Pediatrics demonstrated that antenatal (prior to birth) exposure to magnesium sulfate reduces the risk of cerebellar hemorrhage in premature babies. This may explain the observed neuroprotective effect that leads to a reduced risk of cerebral palsy.
The importance of regular prenatal care
It’s also very important to be as healthy as possible before deciding to get pregnant and throughout the pregnancy. Poor nutrition, smoking, drug abuse, and overuse of alcohol can also lead to premature birth.
Continue to visit with your doctor regularly and ask as many questions as possible. Most likely if you are in any discomfort, your doctor can help you out and determine if it is a serious matter or not. He can then assure you and your baby are safe and on the right path to a successful birth. Continue receiving routine blood work, imaging and ultrasounds to ensure your baby’s growth and safety throughout your pregnancy.
It’s also critical for mothers to get all the proper nutrients throughout their pregnancy and they need to take proper care of their bodies in order to best protect the baby. It’s advised to take prenatal vitamins and try to stay active and exercise as much as your body allows. Gentle exercise helps cope with any posture changes and any other strains your pregnancy can cause on muscles and joints.
Regardless of circumstances, remember that prevention is the best treatment. Preconception planning with smoking cessation, weight reduction for obese mothers, dietary supplementation for the nutritionally deficient, and improving or controlling other medical conditions before you get pregnant will have the most impact on any pregnancy. It will ultimately improve your chances the most in preventing preterm delivery.
Complications of premature birth
Immediate consequences of prematurity
The immediate consequences of prematurity can be serious, including:
- under-developed lungs
- bleeding in the brain
- intestinal problems
- serious breathing problems
Long-term impacts of premature birth
Premature infants are also at a higher risk of developing long-term disabilities since major organs may not be developed enough to work on their own. Throughout a pregnancy, the baby is continuing to grow and develop, especially in the final months and weeks. For example, 37 weeks into a pregnancy, the baby’s liver, brain, and lungs are still developing.
These are some of the long term issues that preemies are at a higher risk of experiencing that can drastically impact their quality of life include:
- Cerebral palsy and other neurological disorders, that can lead to developmental delay and issues with learning.
- Behavior problems and mental health conditions
- Issues with their lungs that lead to breathing problems, including asthma and bronchopulmonary dysplasia
- Dental and vision problems, as well as hearing loss
- Problems with the intestines that can impact feeding
- More susceptible to infections
The role of the Neonatal Intensive Care Unit (NICU)
The many serious short and long-term consequences of prematurity explain why preemies are immediately transferred to the Neonatal Intensive Care Unit (NICU). This gives them the best chance to receive the most optimal treatments possible to help reduce the risk of developing these long-term disabilities.
What is a NICU?
The NICU is the nursery in the hospital that provides 24-hour care to premature or sick newborns. There are four levels of care for babies in hospitals including:
- Level I, Well Newborn Nursery
- Level II, Special Care Nursery
- Level III, NICU.
- Level IV, Regional NICU.
Babies can move from level to level based on their condition and the progress they’ve made. Those in Level III and Level IV care require around the clock attention. In order for a baby to be moved to a lower level, we look for a few things. In terms of health, we look for how strong they are that day, and if they’re able to improve their breathing. We also see if they are gaining adequate weight and what other activities, they are ready for such as being stable enough for parents to hold and if they can move out of an incubator to a crib.
What can parents expect in the NICU?
When you first enter a NICU, you may not know what to expect, especially what you are seeing and what you are hearing. First, sanitation is the most crucial part before even entering the NICU, you must wash your hands thoroughly because infection can spread to infants much easier than a normal person. That is why the first item you will notice all around the unit is soap and hand sanitizer dispensaries everywhere.
There may be a time when you enter the NICU and you can hear a pin drop because lights are dimmed and it’s quiet. Babies in the NICU can be overwhelmed by too much noise and light so the importance of keeping the unit quiet can’t be ignored.
You either will see the babies in the NICU in a cot or a covered incubator which is there to manage and control the temperature of the babies’ body. Depending on what else they need you may also see:
- Machines measuring the amount of fluid and medicine the baby is getting
- Ventilators for breathing
- Special cooling beds
- Monitors measuring heart rate, oxygen levels, and breathing
Day to day in the NICU
In terms of what goes on in the NICU day-to-day, there are a variety of medical personnel involved. There are nurses providing routine monitoring, starting IVs, feedings, and doing blood tests.
Respiratory therapists manage the baby’s ventilator. Occupational and physical therapists provide exercises and stretching while dieticians manage daily feedings and lactation consultants support breastfeeding. Nurse Practitioners provide close follow-ups and us neonatologists provide supervision and management of the entire team and unit.
How has COVID-19 impacted premature birth and NICU care?
COVID has affected every aspect of our care and presented many challenges. COVID-infected or exposed parents may not have been allowed to visit their newborn in the NICU. Sometimes, spouses and other labor support people were not allowed to attend the delivery because of the lockdown. The institution of these rules only compounded the already stressful experience of having a baby in the NICU.
Nursing and hospital staff being sick has also stretched many other employees to put in longer days and weeks, and longer times away from their own families. Healthcare workers are “exposed” every day and have to carry that burden back home to their families. The virus has taken a toll on every person and profession, but healthcare workers, especially those on the front lines, are dealing with a tremendous amount of stress.
What new challenges has COVID-19 presented in terms of the health of the baby?
COVID-19 has brought an entirely new set of issues regarding the baby’s health and resulted in new guidelines to incorporate in our plans.
We had to examine:
- The virus’s routes of transmission including respiratory droplets during the postnatal period, as well as possible intrauterine, intrapartum, or peripartum transmission.
- How to present it clinically as well as how severe the disease is if a child gets it.
- How often and when to test the baby.
- How to control and prevent the spread if a baby is found positive for the virus.
Another issue is keeping vital traditions and practices in place while adjusting to new protocols. A newborn preemie needs to be in contact with both parents, especially the mother, as it consists of well-established health benefits and faster development with bonding, breastfeeding, and other imperative things for their growth.
Recent developments in the premature birth space
The recent developments of progesterone therapy have been encouraging although there are some limitations with it. According to a 2017 study, progesterone therapy is applicable to only a small percentage of pregnant women (primarily those with a shortened cervix and those with a history of previous preterm birth. Consequently, the benefits to the general population are limited. However, several studies have shown that conducting population-based cervical screening programs combined with progesterone therapy is promising.
To conclude, it has been a difficult year for healthcare workers and families who have dealt with a premature birth over the last few months. Premature birth awareness is extremely important, and we’re continuing to better understand and treat this condition. Those thinking of having a child, are currently carrying a child or are already a parent of a preemie with another one on the way, need to take the correct measures to help prevent preterm labor. However, there are encouraging signs of progress in the space and treatment can only improve from here.