Newborns Seen at PH Risk if Fetal Growth Poor and Meconium Inhaled at Birth

Newborns were seen to be at an increased risk of pulmonary hypertension (PH) if they developed poorly while in the womb and had meconium aspiration syndrome, meaning they inhaled their feces during birth, a study from Pakistan reported. 

The study, “The frequency of pulmonary hypertension in newborn with intrauterine growth restriction,” was published in the journal Nature Scientific Reports. 

PH in newborns is associated with a condition called intrauterine growth restriction (IUGR), characterized by poor fetal growth while in the mother’s womb. IUGR is mostly caused by an inadequate oxygen supply to the developing baby or poor maternal nutrition and a low birth weight for her child. 

Restricted fetal growth also increases the risk of meconium aspiration syndrome, in which a newborn breathes meconium — his or her first feces — and amniotic fluid into the lungs around the time of delivery. 

Newborns with IUGR can also experience a sustained lack of oxygen to the brain (birth asphyxia), and respiratory distress syndrome, in which their lungs fail to expand fully after birth because they are unable to make enough surfactants. This syndrome is most often found in premature babies.

IUGR’s incidence is estimated to be six times higher in developing countries than in developed countries, the study stated.

“As Pakistan is the developing country, the incidence of mortalities and injuries caused by IUGR associated PH is higher. In this scenario, it is necessary to reduce the burden of IUGR linked PH,” it added.

Researchers at Government College University Faisalabad investigated the incidence of PH in 96 newborns, up to 28 days old, with IUGR. As a comparison group, 38 newborns without IUGR were also analyzed.

The influence of factors such as sex, gestational age, birth weight, and weight percentile (compared to other infants) for gestational age on the development of PH was assessed. Incidences of meconium aspiration, respiratory distress syndrome, and birth asphyxia were also analyzed.

The pulmonary arterial pressure of all babies was measured via echocardiogram. 

Analysis revealed that roughly one-third of babies (33.3%; 32 newborns) with IUGR had PH, and around 63.1% (24 newborns) of those without IUGR also had this disorder.

Interestingly, all newborns with IUGR and meconium aspiration had PH. In the group of babies without IUGR, eight out of 12 with meconium aspiration were diagnosed with PH.

About 23% of IUGR infants had respiratory distress syndrome and 34.4% had birth asphyxia. Among babies without IUGR, 31.5% had respiratory distress syndrome and 36.8% had birth asphyxia.

No significant relationship was found between the occurrence of PH in IUGR infants and gender, gestational age, or weight percentile for gestational age. 

A statistical analysis found that meconium aspiration syndrome was “strikingly associated” with PH.

“Our data suggest a highly significant association of MAS [meconium aspiration syndrome] with PH in IUGR neonates … but [birth asphyxia], [respiratory distress syndrome], gender, [gestational age] and [weight] as a non-significant risk of PH,” researchers wrote.

An assessment of PH severity in the 96 IUGR babies identified 12 with mild hypertension (20–40 mmHg), 12 with moderate hypertension (41–60 mmHg), and eight with severe hypertension (higher than 60 mmHg). These results indicated “a varying degree of IUGR associated PH,” the researchers wrote.

Taken together, the results suggest “that restricted growth inside the uterus enhances the risk of PH in neonates,” the team concluded, adding that “MAS is a IUGR dependent risk factor of PH in neonates.”

“The documented presence of PH demands further investigations about the potential risk factors involved in the development of PH in IUGR neonates,” the researchers wrote.