Chorionic vascular "fit" in the human placenta: Relationship to fetoplacental outcomes.

BACKGROUND: Novel measures of the chorionic plate and vessels are used to test the hypothesis that variation in placental structure is correlated with reduced birth weight (BW) independent of placental weight (PW), suggesting functionally compromised placentas. METHODS: 916 mothers recruited to the Pregnancy, Infection and Nutrition Study delivering singleton live born infants at >30 gestational weeks had placentas collected, digitally photographed and weighed prior to formalin fixation. The fetal-placental weight ratio (FPR) was calculated as birthweight/placental weight. Beta (beta) was calculated as ln(PW)/ln(BW). Chorionic disk perimeter was traced and chorionic surface shape (CS) area was calculated. "Fit" was defined as the ratio of the area of the vascular to the full chorionic surface area. The sites at which chorionic vessels dived beneath the chorionic surface were marked to calculate the chorionic surface vessel (CV) area. The centroids of shapes, the distance between centroids and other measures of shape irregularities were calculated. Principal components analysis (PCA) created three independent factors. Factors were used in regression analyses to explore relations to birth weight, trimmed placental weight, FPR, and beta. Specific measures of shape irregularity were also examined in regression analyses for interrelationships and to predict birth weight, placental weight, FPR, and beta. RESULTS: Variables related to disk size (CS area, perimeter) were correlated with BW, GA, trimmed PW and beta. "Fit" (the ratio of CV area to CS area), measures of shape irregularities, and the distance between the cord insertion and the centroids of surface and vascular areas were also correlated with one or more of the clinical outcome variables. PCA yielded three factors that had independent effects on birth weight, placental weight, the fetal-placental weight ratio, and beta (each p < 0.0001). Addition of GA did not alter the factors' associations with outcomes. Chorionic "fit" (ratio of areas), also included within the factor analysis, was a positive predictor of birth weight (p = 0.005) and FPR (p = 0.002) and a negative predictor of beta (p = 0.01). Fit was statistically significantly associated with greater distances between the umbilical cord insertion site and the CS (p < 0.001) and CV centroids (p < 0.001), and to lesser displacement between CS and CV centroids (p < 0.001). CONCLUSIONS: Measures of CS and CV account for variation in placental efficiency defined by beta, independent of GA. Macroscopic placenta measurements can identify suboptimal placental development.

Alteration in vaginal microflora, douching prior to pregnancy, and preterm birth.

We aimed to determine the relationship of douching prior to pregnancy and bacterial vaginosis (BV) during pregnancy on preterm birth, addressing individual and joint effects. We used a prospective cohort study and assessed vaginal microflora using gram stains and Nugent's criteria. Douching behaviour was based on self-report about the 12 months prior to pregnancy. Preterm births were categorised as spontaneous or medically indicated. A total of 2561 women provided vaginal specimens and 1492 provided self-reports on douching behaviour. Bacterial vaginosis assessed at 24-28 weeks' gestation in the absence of douching prior to pregnancy was associated with spontaneous preterm birth (odds ratio = 2.74 [95% confidence interval 1.13, 6.66]) as was douching in the absence of BV (OR = 2.20 [1.29, 3.75]). The combination of BV and douching was unrelated to spontaneous or medically indicated preterm birth. We concluded that acute alterations in vaginal microflora at mid-pregnancy or douching prior to pregnancy were associated with an increased risk of preterm birth, but the combination did not appear to increase the risk further than would be expected.

Attitudes toward participation in a pregnancy and child cohort study.

While epidemiological studies aim for high participation rates, it is becoming increasingly difficult to recruit and retain participants in lengthy observational studies. We surveyed women who recently participated in the Pregnancy, Infection, and Nutrition Study during their pregnancy to learn more about what initially motivated them to participate in the study, their attitudes about the study protocol, and whether they would allow their child to participate in future studies. Most women were motivated by their interest in science and learning about their pregnancy. In general, women felt quite comfortable with most aspects of the study. Consent forms, telephone interviews and self-administered questionnaires were the most acceptable components of the study, but even specimen collection was well tolerated by this cohort. Women were less comfortable with the possibility of their child participating in future research. This survey confirmed that once women are enrolled, they tend to be willing to complete most components of an intensive study, suggesting that initial efforts for recruitment are most important.

Measures of placental growth in relation to birth weight and gestational age.

Fetal growth depends in part on placental growth. The authors tested placental measures derived from digital images for reliability and to evaluate their association with birth weight and gestational age. A total of 628 women recruited into the Pregnancy, Infection, and Nutrition Study, a prospective cohort study of preterm birth in central North Carolina between 2002 and 2004, delivered singleton liveborn infants after 24 completed weeks' gestation. Novel chorionic plate morphometric parameters captured off digital images of the gross placenta were analyzed as estimators of gestational age and birth weight. Without acknowledgment to placental weight, digitally obtained lateral chorionic plate growth measures accounted for 17 percent of gestational age variance and 35 percent of birth weight variance, overall. Chorionic plate measures accounted for 10 percent of birth weight variance beyond that accounted for by placental weight alone. Among preterm births, 34 percent of gestational age variance and 63 percent of birth weight variance were accounted for by lateral chorionic plate growth measures. Intraclass correlation coefficients for the novel digital measures ranged from 0.96 to 0.98. Reliable digital measures of lateral chorionic plate growth estimate birth weight variance more strongly than gestational age, project variance that is not accounted for by placental weight, and project these outcomes to a greater degree in preterm births than at term.

Diagnosis of bacterial vaginosis from self-obtained vaginal swabs.

OBJECTIVE: To determine the concordance between vaginal fluid Gram stains and pH obtained at speculum exam with similar stains and pH prepared from self-obtained vaginal swabs. METHODS: Using vaginal fluid Gram stain, 129 pregnant women were screened for bacterial vaginosis at 24 to 29 weeks' gestation. Two smears were collected from each woman during the same prenatal visit: the first was prepared from a self-obtained vaginal swab and the second from a physician-obtained speculum examination. Vaginal pH was recorded for each swab. Kappa coefficient was used to quantify agreement between the two sets of results. RESULTS: When compared with the physician-obtained smear, the ability of the self-obtained Gram stain to diagnose bacterial vaginosis had a sensitivity of 77%, specificity of 97%, positive predictive value of 71% and negative predictive value of 97%. There was substantial agreement (weighted kappa=0.82) between the two techniques in the ability to determine the grade of vaginal flora. CONCLUSION: When compared with physician-obtained vaginal smears, self-obtained smears have substantial agreement in the diagnosis of bacterial vaginosis.