Risk assessment during pregnancy and labor: optimal fetal growth and monitoring of contractions

Abstract

This thesis focuses on risk assessment during pregnancy and labor. Part 1 of this thesis describes risk assessment during pregnancy concentrating on fetal growth in relation to perinatal morbidity, perinatal mortality and implications for maternal health. Perinatal mortality related to fetal growth according to gestational age and birth weight was studied in singleton and twin pregnancies based on perinatal registry data in the Netherlands. Overall perinatal mortality is higher in twins than in singletons. However, when taking into account differences in gestational age at delivery, antepartum mortality was significantly lower during the preterm period in twins than in singletons. The later may, among other reasons, be due to a better surveillance of twin pregnancies. For both singletons and twins highest mortality rates were found for children with a birth weight below the 5th centile. For singletons from an immediate survival perspective, optimal fetal growth requires a birth weight between the 80-84th centiles for the population. For twins, optimal birth weight requires a birth weight between the 10-50th centile. After stratification for estimated data on zygosity optimal birth weight for dizygotic twins was comparable to that of singletons and around the 90th centile. Intra-uterine identification of fetuses at risk is extremely important. Ultrasound measurement of fetal growth and Doppler indices is an essential tool in this identification process, however in the term period most of these tools fail to identify the fetus at risk. For prediction of adverse neonatal outcome of near term small for gestational age fetuses, changes from normal to abnormal Doppler parameters with time, were related to impaired outcome, with the cerebro-placental ratio and ductus venosus as the best parameter to identify the SGA fetus at risk. This implies longitudinal monitoring of these variables. A single measurement was not related to outcome. Next to fetal complications, impaired fetal growth also seems to have implications for maternal cardiovascular health. Other maternal placental disorders such as pre-eclampsia and placental abruption are associated with an increased prevalence of cardiovascular (CV) disease risk factors several months after delivery. Women with a history of preterm intra uterine growth restriction, with or without maternal hypertensive disorder, have an altered cardiovascular risk profile several months after pregnancy with increased levels of modifiable cardiovascular risk factors. Part 2 of this thesis focuses on risk assessment during labor by studying a new technique, electromyography, to monitor contractions for identification of inefficient contractions leading to first stage labor arrest followed by cesarean delivery in term nulliparous women. Cesarean delivery rates are increasing worldwide. Conventional uterine contraction monitoring techniques fail to improve outcomes. As spontaneous labor and induced labor differ substantially on multiple levels both groups were studied separately. In term nulliparous women with a singleton pregnancy in cephalic position and spontaneous onset of labor, contraction characteristics measured by uterine EMG correlate with progression of labor and are influenced by labor augmentation. Uterine electromyography shows no correlation with progression of labor in induced labor in nulliparous women with singleton term pregnancies and a fetus in cephalic position.