A description of the methods of the Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be (nuMoM2b)

Abstract

Objective: The primary aim of the "Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be" is to determine maternal characteristics, which include genetic, physiologic response to pregnancy, and environmental factors that predict adverse pregnancy outcomes.

Study design: Nulliparous women in the first trimester of pregnancy were recruited into an observational cohort study. Participants were seen at 3 study visits during pregnancy and again at delivery. We collected data from in-clinic interviews, take-home surveys, clinical measurements, ultrasound studies, and chart abstractions. Maternal biospecimens (serum, plasma, urine, cervicovaginal fluid) at antepartum study visits and delivery specimens (placenta, umbilical cord, cord blood) were collected, processed, and stored. The primary outcome of the study was defined as pregnancy ending at <37+0 weeks' gestation. Key study hypotheses involve adverse pregnancy outcomes of spontaneous preterm birth, preeclampsia, and fetal growth restriction.

Results: We recruited 10,037 women to the study. Basic characteristics of the cohort at screening are reported.

Conclusion: The "Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be" cohort study methods and procedures can help investigators when they plan future projects.

Trial registration: ClinicalTrials.gov NCT01322529.

Keywords: adverse pregnancy outcome; cohort study; methods; nulliparous; prediction; pregnancy; psychosocial.

Figure 1

Cross-sections of placental specimens relative to the 1 cm inner diameter of a 2 mL cryovial. Specimens should not press against the inner wall of the cryovial; where liquid medium is used, specimens should be surrounded by the medium. These requirements are satisfied by an 8 mm diameter punch biopsy (panel A) or a scalpel cut specimen with cross-sectional dimensions between 0.7 × 0.7 cm (panel B) and 0.5 × 0.5 cm (panel C). Obtained with a depth of 1 cm, these correspond to a specimen volume of 0.5 cubic cm (panel A) or between 0.5 cubic cm (panel B) and 0.25 cubic cm (panel C).

Figure 2

Locations for collection of placenta and umbilical cord samples. Shown are the locations for the ideal delivery collection. (For the standard delivery collection, ignore the locations for specimens for RNA, protein/metabolites, and DNA/epigenetics, which are obtained only under ideal collection.) Locations for the placenta samples other than for histology are shown with dashed lines, because the sample is to be taken to a depth of 1.3 cm and then 3 mm from the top (i.e., the fetal side) is to be trimmed, resulting in a sample from the interior of the placental thickness, with final length of 1 cm.