Low Waters, Birth Weight Increase Risk for Early PH in Premature Babies

Babies with early PH are more likely to develop bronchopulmonary dysplasia

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

Share this article:

Share article via email
Pulmonary Hypertension in Premature Babies | Pulmonary Hypertension News | early PH | illustration of adults looking at newborn in hospital

Preterm babies who grow with too little amniotic fluid (also called waters), or are born too small for their age, are at greater risk of developing pulmonary hypertension in the first two weeks of life, a meta-analysis study found.

Babies with early pulmonary hypertension (PH) were more likely to develop bronchopulmonary dysplasia (BPD), a breathing problem that occurs when the lungs have not yet developed correctly. They also were more likely to have PH later in infancy and beyond, or to die in the hospital.

The study, “Risk factors of early pulmonary hypertension and its clinical outcomes in preterm infants: A systematic review and meta-analysis,” was published in the journal Scientific Reports.

PH is high blood pressure in the blood vessels that feed the lungs, making it harder for the heart to pump blood into the lungs. It can occur in people of all ages, including babies.

Recommended Reading
Pulmonary Hypertension in Premature Babies | Pulmonary Hypertension News | early PH | illustration of adults looking at newborn in hospital

Prenatal Echocardiograms May Help Predict PH in Newborns 

A baby’s lungs are one of the last organs to develop in the womb, and they will continue to grow even after the baby is born, until they become fully functional. This means the lungs of babies born preterm, or before 37 weeks of pregnancy are completed, are not fully developed.

These babies often have difficulty breathing after birth. The earlier they are born, the more difficulty they will have and the more likely they are to have problems with lung health.

In a Dutch study, more than half of preterm babies were found to have PH, and this put them at greater risk for developing BPD. It also increased their chances of being placed on mechanical ventilation and supplemental oxygen to help them breathe.

Now, a team of researchers in Korea set out to find the factors that increase the risk of pulmonary hypertension in premature babies.

They combined data from eight studies published from 2014 to 2021 with babies born preterm or weighing less than 1,500 grams (about 3.3 pounds) who were diagnosed with early PH in the first two weeks of life.

Of a total of 1,435 babies, 388 developed PH in the first two weeks after birth. An analysis combining all study results found the overall rate of early PH was 24%.

Babies who grew with too little amniotic fluid around them in the womb, a condition called oligohydramnios, had more than double the risk for early PH. For babies born too small for their age, with a birth weight below the 10th percentile, the risk was increased by 83%.

The BPD factor

Six studies (1,101 babies) also reported on BPD, which was defined as needing oxygen for more than 28 days or supplemental oxygen at 36 weeks of postmenstrual age. Postmenstrual age is the gestational age (the time between the first day of the last menstrual period and a baby’s birth) plus the age since the baby’s birth.

Babies with early PH were 68% more likely than babies without pulmonary hypertension to develop moderate-to-severe BPD.

Data from four studies (798 babies) revealed that babies with early PH also were almost three times more likely to have a diagnosis of PH after four weeks of life.

Moreover, early PH was linked to worse survival, or more than double the chance to die in the hospital, according to data from six studies (1,111 babies).

“The findings of the present study suggest the importance of evaluating early [pulmonary hypertension] in preterm infants within 2 weeks of age,” the researchers wrote. They added that babies who grew with too little amniotic fluid or are born with very low weight “will benefit from early screening and continuous monitoring of [PH] using echocardiography.” Echocardiography is a noninvasive test that uses ultrasound waves to check how well the heart is working.