Near-term Pregnancy Research Articles

Accelerated clotting time: An amniotic fluid thromboplastic activity index of fetal maturity

Amniotic fluid in near-term pregnancies contains increasing amounts of free phospholipids and thromboplastins liberated from degenerating, desquamated fetal cells. Mature amniotic fluid is, therefore, likely to accelerate the clotting process. The accelerated clotting time (ACT) was obtained by adding 1.5 ml. of the patient's blood to 1.0 ml. of amniotic fluid in a plastic test tube at 37° C. Sixty-five third-trimester amniotic fluid samples from 28 patients demonstrated increasing “thromboplastic” or clot-accelerating activity with progressing pregnancy. ACT's from 277 amniotic fluid samples were estimated and correlated at the time of amniocentesis with gestation calculated retrospectively from pediatric assessment at birth. This was done in parallel with lecithin/sphingomyelin (L/S) ratio estimations and both were correlated with gestation. The range of ACT's obtained was 30 to 230 seconds. An ACT of less than 110 seconds usually indicated fetal maturity. The transitional zone was 95 to 120 seconds. Of the 277 estimations of ACT, L/S ratio, and gestation there was variance of assessment of maturity between ACT and L/S ratio in 33. L/S ratio gave only 11 (4 per cent) false results, 10 being false negative. ACT gave 22 (7.9 per cent) false results, 21 being false negative. Sixteen of the 22 errors were “transitional.” There were two cases of respiratory distress syndrome in the series, one predicted only by the L/S ratio, the other only by the ACT. Estimation of thromboplastic activity of amniotic fluid with ACT is a quick, simple, reliable method of estimating fetal maturity. Its rapidity and simplicity make it a rival of the shake and Nile blue sulfate tests, the result being available within five minutes of the amniocentesis. No test of fetal maturity is foolproof, and as multiple amniotic fluid estimations are proving more accurate than single estimations, the speed and simplicity of ACT make it an alternative method of amniotic fluid analysis.

A role for prostaglandins in the regulation of the placental blood flows

A model is proposed for the regulation of the placental blood flows to the near-term pregnancy. The model has three features. 1) The maternal uterine and fetal placental tissues can synthesize constrictor and dilator prostaglandins. 2) Prostaglandins can cross the placenta. 3) There must exist a prostaglandin which has a vasodilating action in one of the placental circulations and a vasoconstricting action in the other circulation. Evidence is provided to indicate that in the sheep, prostaglandin E 2 (PGE 2) can cross the placenta and has a vasodilating action in the uterine placental circulation and a vasoconstricting action in the umbilical placental circulation. The placenta and the lung are compared and PGE 2 is shown to have similar actions in each of these organs.

Local regulation of the uterine blood flow by the umbilical circulation.

Observations were made of the responses of the uterine blood flow in the near-term pregnancy to occlusion of the umbilical circulation to a few cotyledons of the near-term sheep placenta and in one placenta of the multiparous rabbit pregnancy. It was found that the uterine blood flow declined to 67% of its predicted value 1 day after umbilical ligation in the sheep placenta and to 61% of its predicted value 1 day after the death of one of the fetuses of the rabbit pregnancy. The change in the uterine blood flow in response to the occlusion of the umbilical blood supply to the adjacent area is a local response and is similar in its time course and magnitude to the response of the whole placenta which has been previously observed by Raye et al. (9). This local response of the uterine blood flow is considered to be evidence that the uterine blood flow is in part determined and controlled by the structural or chemical nature of the adjacent fetal compartment.

Estrogen synthesis by adrenal-placental tissues of the sheep and the iris monkey in vitro.

An experiment was designed to determine whether the interdependent relationship of the placenta and fetal adrenal in estrogen synthesis is unique to human pregnancy or whether it might be a feature of mammalian reproduction more generally. A sheep and an iris monkey (Macaque fasciculata), each with a near-term pregnancy, were selected for study. The placentas and the adrenals of both the mother and fetus were removed and homogenates were prepared as follows: 1) placenta, 2) maternal adrenal, 3) fetal adrenal, 4) placenta plus maternal adrenal, and 5) placenta plus fetal adrenal. Each homogenate was incubated with pregnenolone-7α-3H and appropriate cofactors. Following incubation the following carrier steroids were added: estrone, estradiol, androstenedione, 19-norandrostendione, testosterone and dehydroepiandrosterone. These carrier steroids were purified by conventional techniques and their radiochemical purity was determined by reverse isotope dilution. The synthesis of estrone was demonstrated in all i...

Comparison of amniography and pelvic angiography in the diagnosis of hydatidiform mole.

Hydatidiform mole is a pathologic pregnancy which may present problems in diagnosis. The clinician is faced with a dilemma: he desires to make an early diagnosis but is fearful of interrupting a normal gestation. The purpose of this paper is to compare the findings of the combination of pelvic arteriography and amniography performed in patients with hydatidiform moles. Hydatidiform mole occurs with a frequency of 1 in 2,000 pregnancies in the United States. A slightly higher incidence is noted in the Mexican and Oriental populations. Its early diagnosis is desirable to allow early termination of the abnormal pregnancy and avoid the later complications of hemorrhage associated with spontaneous unattended evacuation, the development of subsequent cancer, or early toxemia. Heretofore, the diagnosis of molar pregnancy has been based on presumptive signs and symptoms such as severe hyperemesis, an early toxemia, persistent uterine spotting or bleeding, uterine enlargement beyond that expected for the gestational dates, abnormally high titers of chorionic gonadotropins, absence of fetal parts on palpation and absence of fetal structures on roentgen examination. Recently, Acosta-Sison (1) described the passage of a uterine sound through the cervix. He noted that if resistance is not felt at the level of the internal os, it is assumed that the normal amniotic sac is absent and the uterus is filled with vesicles which allow passage of the sound. The objections to all the listed signs, symptoms, and tests are their presumptive nature and their dependence generally on negative rather than positive findings. Of course, all of these may be falsely negative or positive—they may be indicative of early threatened abortion, multiple gestation, the limits of normal variation or, as in the case of absent fetal parts on x-ray studies, simply due to the early stage of gestation. What is most desirable is a procedure or test easily performed with readily available equipment, which will give a positive diagnostic result and offer little or no hazard to the mother or to a potentially normal and viable gestation. The technic of amniography was described by Menees et al. (7) in 1930 who employed the procedure for placental localization in near-term pregnancies. Bayan and Apelo (2) reported its value in the diagnosis of hydatidiform mole in 1957. McLain (6) in 1964 reported one case of hydatidiform mole studied by amniography in his series. Pelvic arteriography in the diagnosis of hydatidiform mole was described by Borell and Fernström (3) in 1961. They reported 5 cases in which pelvic angiography was part of the work-up. Material Four cases of hydatidiform mole were studied by both pelvic angiography and amniography prior to evacuation of the uterus. The basic technic of amniography varies little from that originally described by Menees and his co-workers.