Waiting for postterm in healthy women, is it an accident waiting to happen?

Magnitude e características dos nascimentos termo tardio e pós-termo e complicações maternas e neonatais no Brasil, 2011

Este estudo analisou o nascimento termo tardio e pós-termo, avaliando o perfil materno, suas características e as complicações maternas e neonatais. Foram selecionados 23.610 bebês do estudo Nascer no Brasil (2011), sendo realizada uma análise descritiva da população de estudo. A associação entre o nascimento termo tardio e pós-termo e seus desfechos foi efetuada pela utilização de regressões logísticas (valor de p < 0,05). A prevalência encontrada foi de 7,4% para o termo tardio e de 2,5% para o pós-termo, tendo ambos sido mais frequentes nas regiões Norte e Nordeste, em adolescentes, mulheres negras, de baixa escolaridade, multíparas, atendidas no setor público. As gestações termo tardio tiveram maior chance de indução do parto vaginal (OR = 2,02; IC95%: 1,67-2,45), de cesariana (OR = 1,32; IC95%: 1,16-1,52), de laceração grave (OR = 3,75; IC95%: 1,36-10,36) e de uso oxigenoterapia para os recém-nascidos (OR = 1,52; IC95%: 1,02-2,26). Nas gestações pós-termo, os recém-nascidos tiveram menor chance de amamentação ao nascer (OR = 0,74; IC95%: 0,56-0,97) e durante a hospitalização (OR = 0,62; IC95%: 0,40-0,97) e maior chance de nascerem pequenos para a idade gestacional (OR = 4,01; IC95%: 2,83-5,70). Os resultados utilizando somente a ultrassonografia como medida da idade gestacional confirmaram os achados anteriores. Gestações termo tardio e pós-termo ocorrem com maior frequência nas regiões Norte e Nordeste e em mulheres com maior vulnerabilidade social, associando-se a complicações maternas e neonatais.

Immediate perinatal outcomes of postterm deliveries

OBJECTIVE

To investigate whether postterm pregnancy (≥42 0/7 weeks' gestation) increases the risk for adverse perinatal outcome.

STUDY DESIGN

In this population based cohort study, all singleton deliveries occurring between 1991 and 2014 in a tertiary medical center were included. Pregnancy and perinatal outcomes were compared between postterm and term deliveries (37 0/7 to 41 6/7 weeks' gestation). Preterm deliveries, unknown gestational age, congenital malformations, and multiple gestations, were excluded. The association between postterm and adverse perinatal outcomes was evaluated using a general estimation equation (GEE) multivariable analyses.

RESULTS

During the study period, 226,918 deliveries were included in the analysis. Of them, 95.9% (n = 217,544) were term and 4.1% (n = 9374) were postterm. Post-term pregnancies were more likely to be complicated with oligohydramnios, macrosomia, meconium stained amniotic fluid, shoulder dystocia, low Apgar scores, and hysterectomy (p < .05 in all). Perinatal mortality rates were significantly higher at postterm as well. Using the GEE model, the association between postterm and total perinatal mortality persisted (OR = 1.73, 95%CI 1.2-2.4), as well as specifically intrauterine fetal death (OR = 1.76, 95%CI 1.1-2.7) and intrapartum death (OR = 3.71, 95%CI 1.3-10.4).

CONCLUSIONS

Post-term delivery involves higher rates of adverse perinatal outcomes and is independently associated with significant perinatal mortality.

A mouse model of antepartum stillbirth

BACKGROUND

Many stillbirths of normally formed fetuses in the third trimester could be prevented via delivery if reliable means to anticipate this outcome existed. However, because the etiology of these stillbirths is often unexplained and although the underlying mechanism is presumed to be hypoxia from placental insufficiency, the placentas often appear normal on histopathological examination. Gestational age is a risk factor for antepartum stillbirth, with a rapid rise in stillbirth rates after 40 weeks' gestation. We speculate that a common mechanism may explain antepartum stillbirth in both the late-term and postterm periods. Mice also show increasing rates of stillbirth when pregnancy is artificially prolonged. The model therefore affords an opportunity to characterize events that precede stillbirth.

OBJECTIVE

The objective of the study was to prolong gestation in mice and monitor fetal and placental growth and cardiovascular changes.

STUDY DESIGN

From embryonic day 15.5 to embryonic day 18.5, pregnant CD-1 mice received daily progesterone injections to prolong pregnancy by an additional 24 hour period (to embryonic day 19.5). To characterize fetal and placental development, experimental assays were performed throughout late gestation (embryonic day 15.5 to embryonic day 19.5), including postnatal day 1 pups as controls. In addition to collecting fetal and placental weights, we monitored fetal blood flow using Doppler ultrasound and examined the fetoplacental arterial vascular geometry using microcomputed tomography. Evidence of hypoxic organ injury in the fetus was assessed using magnetic resonance imaging and pimonidazole immunohistochemistry.

RESULTS

At embryonic day 19.5, mean fetal weights were reduced by 14% compared with control postnatal day 1 pups. Ultrasound biomicroscopy showed that fetal heart rate and umbilical artery flow continued to increase at embryonic day 19.5. Despite this, the embryonic day 19.5 fetuses had significant pimonidazole staining in both brain and liver tissue, indicating fetal hypoxia. Placental weights at embryonic day 19.5 were 21% lower than at term (embryonic day 18.5). Microcomputed tomography showed no change in quantitative morphology of the fetoplacental arterial vasculature between embryonic day 18.5 and embryonic day 19.5.

CONCLUSION

Prolongation of pregnancy renders the murine fetus vulnerable to significant growth restriction and hypoxia because of differential loss of placental mass rather than any compromise in fetoplacental blood flow. Our data are consistent with a hypoxic mechanism of antepartum fetal death in human term and postterm pregnancy and validates the inability of umbilical artery Doppler to safely monitor such fetuses. New tests of placental function are needed to identify the late-term fetus at risk of hypoxia to intervene by delivery to avoid antepartum stillbirth.

Maternal characteristics of pregnancies with intrauterine fetal demise

OBJECTIVE

To identify maternal characteristics independently associated with pregnancies resulting in intrauterine fetal demise (IUFD).

STUDY DESIGN

This was a population-based cohort study of all births taking place at the McGill University Health Centre in Montreal, Canada, between 2001 and 2007, using the McGill University Obstetrics and Neonatal Database. Maternal characteristics were compared between pregnancies that resulted in IUFD and control pregnancies resulting in live newborns. A logistic regression analysis was constructed to identify parameters independently associated with IUFD.

RESULTS

We identified 20,744 births during the study period, 87 of which were complicated by IUFD. Mothers with IUFD were more likely to be younger, with less formal education, higher rates of smoking during pregnancy, and more fetal anomalies (42.5% vs. 7.5%, P<0.001). After exclusion of pregnancies with congenital and/or chromosomal abnormalities, less formal education (7 vs. 13.6 school years, P<0.001) and smoking during pregnancy (24% vs. 7.7%, P<0.001) remained significantly more common in pregnancies resulting in IUFD. In the multivariable regression analysis both smoking and number of maternal school years were independently associated with IUFD pregnancies (OR 2.22 for smoking, P=0.007 and OR 0.865 for number of school years, P<0.001).

CONCLUSION

Lower levels of education and smoking during pregnancy are independent predictors of IUFD.