We have developed a real-time quantitative PCR assay to measure the concentration of fetal DNA in maternal plasma and serum. Our results show that fetal DNA is present in high concentrations in maternal plasma, reaching a mean of 25.4 genome equivalents/ml (range 3.3-69. 4) in early pregnancy and 292.2 genome equivalents/ml (range 76. 9-769) in late pregnancy. These concentrations correspond to 3.4% (range 0.39%-11.9%) and 6.2% (range 2.33%-11.4%) of the total plasma DNA in early and late pregnancy, respectively. Sequential follow-up study of women who conceived by in vitro fertilization shows that fetal DNA can be detected in maternal serum as early as the 7th wk of gestation and that it then increases in concentration as pregnancy progresses. These data suggest that fetal DNA can be readily detected in maternal plasma and serum and may be a valuable source of material for noninvasive prenatal diagnosis.

Fetal DNA has been detected in maternal plasma during pregnancy. We investigated the clearance of circulating fetal DNA after delivery, using quantitative PCR analysis of the sex-determining region Y gene as a marker for male fetuses. We analyzed plasma samples from 12 women 1-42 d after delivery of male babies and found that circulating fetal DNA was undetectable by day 1 after delivery. To obtain a higher time-resolution picture of fetal DNA clearance, we performed serial sampling of eight women, which indicated that most women (seven) had undetectable levels of circulating fetal DNA by 2 h postpartum. The mean half-life for circulating fetal DNA was 16.3 min (range 4-30 min). Plasma nucleases were found to account for only part of the clearance of plasma fetal DNA. The rapid turnover of circulating DNA suggests that plasma DNA analysis may be less susceptible to false-positive results, which result from carryover from previous pregnancies, than is the detection of fetal cells in maternal blood; also, rapid turnover may be useful for the monitoring of feto-maternal events with rapid dynamics. These results also may have implications for the study of other types of nonhost DNA in plasma, such as circulating tumor-derived and graft-derived DNA in oncology and transplant patients, respectively.

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The monitoring of fetal weight is an important aspect of antenatal care. To construct an individually adjustable standard, we developed a model to link the predicted birth weight to a fetal weight curve which outlines how this weight is to be reached in an uncomplicated pregnancy. A formula was derived which describes the median fetal weight at each gestation as a proportion of the optimal term weight, and also defines the 90th and 10th centile curves as normal limits. We analyzed a birth weight database of 38,114 singleton, routine ultrasound-dated pregnancies resulting in term deliveries. By stepwise multiple regression analysis, we derived coefficients for the factors that act as variables on term birth weight in our population. Apart from gestational age and sex, the maternal height, weight at first visit, ethnic group, parity and smoking all have significant and independent effects on birth weight. The variation due to ethnic group appears to be physiological in this population. Smoking is associated with a reduction in birth weight, which is independent of maternal physique and related to the number of cigarettes per day as reported at the first visit. We have developed a software program which calculates, on the basis of pregnancy variables entered at the first visit, an adjusted normal range for fetal size. This can be printed out as a chart and used for antenatal surveillance of growth.

Objective: To assess the prevalence and impact of overweight and obesity in an Australian obstetric population. Design, setting and participants: The Mater Mother's Hospital (MMH), South Brisbane, is an urban tertiary referral maternity hospital. We reviewed data for the 18 401 women who were booked for antenatal care at the MMH, delivered between January 1998 and December 2002, and had a singleton pregnancy. Of those women, 14 230 had an estimated pre‐pregnancy body mass index (BMI) noted in their record; 2978 women with BMI ≤ 20 kg/m2 were excluded from further study; the remaining 11 252 women were divided into four categories: “normal” (BMI 20.01–25 kg/m2), “overweight” (BMI 25.01–30 kg/m2), “obese” (BMI 30.01–40 kg/m2) and “morbidly obese” (BMI > 40 kg/m2). Main outcome measures: Prevalence of overweight and obesity in an obstetric population; maternal, peripartum and neonatal outcomes associated with raised BMI. Results: Of the 14 230 women, 6443 (45%) were of normal weight, and 4809 (34%) were overweight, obese or morbidly obese. Overweight, obese and morbidly obese women were at increased risk of adverse outcomes (figures represent adjusted odds ratio [AOR] [95% CI]): hypertensive disorders of pregnancy (overweight 1.74 [1.45–2.15], obese 3.00 [2.40–3.74], morbidly obese 4.87 [3.27–7.24]); gestational diabetes (overweight 1.78 [1.25–2.52], obese 2.95 [2.05–4.25], morbidly obese 7.44 [4.42–12.54]); hospital admission longer than 5 days (overweight 1.36 [1.13–1.63], obese 1.49 [1.21–1.86], morbidly obese 3.18 [2.19–4.61]); and caesarean section (overweight 1.50 [1.36–1.66], obese 2.02 [1.79–2.29], morbidly obese 2.54 [1.94–3.32]). Neonates born to obese and morbidly obese women had an increased risk of birth defects (obese 1.58 [1.02–2.46], morbidly obese 3.41 [1.67–6.94]); and hypoglycaemia (obese 2.57 [1.39–4.78], morbidly obese 7.14 [3.04–16.74]). Neonates born to morbidly obese women were at increased risk of admission to intensive care (2.77 [1.81–4.25]); premature delivery (< 34 weeks’ gestation) (2.13 [1.13–4.01]); and jaundice (1.44 [1.09–1.89]). Conclusions: Overweight and obesity are common in pregnant women. Increasing BMI is associated with maternal and neonatal outcomes that may increase the costs of obstetric care. To assist in planning health service delivery, we believe that BMI should be routinely recorded on perinatal data collection sheets.

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Background: Recently, much interest has been generated on the fetomaternal transfer of nucleated cells and plasma DNA. However, there has been no systematic quantitative comparison of these two directions and two modalities of trafficking within the same study population. Methods: The fetus-to-mother transfer of nucleated cells and plasma DNA in pregnant women carrying male babies was studied using a real-time quantitative PCR assay for the SRY gene. For mother-to-fetus transfer, real-time quantitative PCR assays for the insertion/deletion polymorphisms involving the glutathione S-transferase M1 and angiotensin-converting enzyme genes were used. Results: Of the 50 informative mother-baby pairs, maternal DNA was detected in the cellular fraction of umbilical cord blood in 24% of cases (12 of 50), at a median fractional concentration of 2.6 × 10−4 (interquartile range, 1.7 × 10−4 to 3.6 × 10−4). In the plasma fraction of cord blood, maternal DNA was detected in 30% (15 of 50) of cases at a median fractional concentration of 3 × 10−3 (interquartile range, 1 × 10−3 to 1.6 × 10−2). For the other direction of trafficking, fetus-to-mother transfer of nucleated cells was detected in 26% of cases (13 of 50) at a median fractional concentration of 3.2 × 10−4 (interquartile range, 0.6 × 10−4 to 7.6 × 10−4). In the plasma fraction, fetal DNA was detected in 100% of maternal plasma (50 of 50) at a median fractional concentration of 3 × 10−2 (interquartile range, 1.4 × 10−2 to 5.3 × 10−2). Conclusions: This study indicated that significantly more fetal DNA is present in the plasma of pregnant women compared with DNA from the cellular fraction of maternal blood. In addition, maternal DNA was demonstrated in both the cellular and plasma fractions of cord blood after delivery. This study has therefore determined the fundamental quantitative values for the bidirectional fetomaternal cellular and plasma DNA traffic.