Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be

The Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) established the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be (nuMoM2b) to study women for whom the current pregnancy will lead to their first delivery (nulliparas). About 40% of pregnant women in the United States are nulliparas. Because little or no information from previous pregnancy outcomes is available to guide assignment of risk or mitigating interventions, adverse pregnancy outcomes in nulliparas are especially unpredictable. The underlying mechanisms of adverse pregnancy outcomes such as preterm birth, preeclampsia, fetal growth restriction and stillbirth are interrelated and therefore will be evaluated as part of this study. The information gained will benefit women who are pregnant or who are considering pregnancy and their physicians. In addition, the knowledge will support future research aimed at improving care and health outcomes for a critical group of at-risk women who are currently understudied.

The study is a prospective cohort study of a racially/ethnically/geographically diverse population of 10,038 nulliparous women with singleton gestations. The women undergo intensive research assessments during the course of their pregnancies to study the mechanisms for and prediction of adverse pregnancy outcomes (APOs) in women in their first pregnancy. The APOs of primary interest are preterm birth, preeclampsia and fetal growth restriction.

The goals of the study are to 1) determine maternal characteristics, including genetics, epigenetics, and physiological response to pregnancy as well as environmental factors that influence and/or predict adverse pregnancy outcome; 2) identify specific aspects of placental development and function that lead to adverse pregnancy outcome; and 3) characterize genetic, growth, and developmental parameters of the fetus that are associated with adverse pregnancy outcome.

Eight academic medical centers or sites had primary responsibility for enrollment and follow-up of study participants. Several of these sites collected data through additional academic research centers or nearby hospitals (subsites). A Data Coordinating and Analysis Center (DCAC) provided input to the protocol, manages the data, and analyzes the data. Investigators from these institutions have established a partnership with NICHD staff to develop and implement the study protocol and ancillary studies that acquire and analyze data to identify biomarkers and understand the mechanism and prediction of preterm birth and other adverse pregnancy outcomes.

Nulliparous women with an in utero singleton gestation between 6 weeks 0 days and 13 weeks 6 days of pregnancy were recruited through the eight clinical sites and their subsites. Mechanisms were created in the various prenatal clinics associated with the sites to identify eligible nulliparous women with singleton pregnancies. Once enrolled, a participant was followed for the duration of her pregnancy by research staff at the clinical site. Study visits were scheduled at four times during the pregnancy: 6 weeks 0 days through 13 weeks 6 days estimated gestational age (EGA), 16 weeks 0 days through 21 weeks 6 days EGA, 22 weeks 0 days through 29 weeks 6 days EGA, and at the time of delivery. Data were collected through personal interview, self-administered questionnaires, clinical measurement, chart abstraction, and collection of biological specimens (blood, urine, cervico-vaginal fluid). Additional data (i.e., sleep breathing assessments, actigraphy, fetal adrenal gland measurements) were collected through ancillary research studies on subsets of the enrolled women. The set-ups for screening, enrollment and follow-up of participants varied by clinical site and subsite. However, in each setting, the clinical site staffs included study investigators, research nurses, research assistants and sonographers. Clinical site staffs were trained to interview participants, collect and process samples, conduct various research tests, and input data. Data are managed at the DCAC. Specimens are stored at the NICHD specimen repository for later analysis.

Inclusion criteria

• Nullipara - Pregnant women with no prior pregnancy lasting 20 weeks 0 days or greater.
• Viable singleton gestation - a single living fetus with fetal cardiac activity at the most recent ultrasound before enrollment
• Between 6 weeks 0 days and 13 weeks 6 days project estimated gestational age (EGA) at first study visit.
• Intend to deliver at a participating hospital.

Exclusion criteria

• Participant age <13 years.
• History of 3 or more spontaneous abortions.
• Fetal malformation evident at or before enrollment that is likely lethal (e.g., anencephaly, hydrops, diffuse subcutaneous edema or cystic hygroma, ectopic cordis, encephalocele).
• Known fetal aneuploidy (based on chorionic villus sampling).
• Surrogate pregnancy (donor oocyte pregnancy).
• Multifetal reduction.
• Participating in an intervention study that is anticipated to influence maternal or fetal morbidities/mortality unless it is determined before enrollment that the study code will be made available.
• Woman previously enrolled in this study, including those consented but delivered before 20 weeks 0 days gestation.
• Planned pregnancy termination.
• Unable to provide informed consent.