Randomized Trial of Maternal Progesterone Therapy to Improve Neurodevelopmental Outcomes in Infants With Congenital Heart Disease

In the United States, approximately 1 in every 100 newborns is diagnosed with congenital heart disease (CHD). Many of these newborns (25%-35%) will require either corrective or palliative open heart surgery. As recently as the 1960's, only 20% of newborns with critical CHD survived to adulthood. Today, thanks to better diagnostic technologies and methods (including prenatal diagnosis), advances in surgery, and improved postoperative care, early survival is over 90%. However, with improved early outcomes has come the sobering recognition that there is an ongoing risk of late mortality, as well as significant morbidity for these children. In particular, neurodevelopmental disability is now recognized as the most common complication of critical CHD (i.e. those patients requiring cardiac surgery in infancy) and has the most negative impact on quality of life, academic performance and opportunity for independence as an adult.

The altered fetal hemodynamics secondary to CHD lead to decreased blood flow and/or oxygen delivery to the fetal brain. In turn, this impairment in blood flow and oxygenation results in impaired brain growth and altered structural and cellular maturation, particularly of the white matter. Fetal MRI studies have shown that during the third trimester, normally a time of rapid brain growth and development, brains of infants with CHD fail to grow at the same rate as the brains of fetuses without CHD. This growth delay results in microcephaly, immature cellular elements of the white matter and decreased cortical folding at birth. It has been demonstrated that brain immaturity at birth is a primary major risk factor underlying the hypoxic-ischemic white matter brain injury and subsequent neurodevelopmental disability seen in over 50% of infants following surgery for CHD. In addition, there is increasing evidence in the CHD population that even late pre-term birth (prior to 39 weeks GA) is associated with increased mortality, increased peri-operative morbidity, and worse neurodevelopmental outcomes.

Progesterone is an essential hormone in the occurrence and maintenance of pregnancy. Progesterone administration has also been shown to be neuroprotective in a variety of clinical situations, including traumatic brain injury (TBI). Sex steroid hormones, including progesterone, are critically involved in axonal myelination, forming the basis of white matter connectivity in the central nervous system (CNS). Progesterone and its metabolites not only promote the viability and regeneration of neurons, but also act on myelinating glial cell oligodendrocytes in the CNS and play an important role in the formation of myelin sheaths. Progesterone has also been shown to increase myelination and enhance maturation of immature oligodendrocytes progenitor cells to mature oligodendrocytes, which are more resistant to hypoxic/ischemic injury. Therapeutic administration of progesterone has also been demonstrated to prevent preterm birth. Thus, there are two potential mechanisms by which pre-natal progesterone therapy may improve neurodevelopmental outcomes in neonates with CHD: 1) a direct neuroprotective effect, and 2) decreasing the occurrence of pre-term birth.

Study Objectives

Primary: Develop preliminary evidence to support a multi-institutional study to determine whether, in women carrying fetuses (maternal-fetal dyad) with CHD, prophylactic vaginal natural progesterone therapy is neuroprotective, and compared to placebo improves neurodevelopmental outcomes at 18 months of age.