The guidelines of timing repeat cesarean section at Parkland hospital do not include mandatory amninocentesis to measure the amnionic fluid lecithin/sphingomyelin ratio. Instead, the following information is used to identify fetal maturity; (1) the date of onset of the last normal spontaneous menstrual period if accurately known, (2) ultrasonic estimates of fetal age performed in the first trimester or soon thereafter, (3) serial measurements of uterine fundal height begun before mid-pregnancy, (4) the time when fetal heart sounds were first heard with an unamplified fetoscope and (5) the estimated fetal size.
Delivery is carried out after 38 completed weeks of gestation, based on the last menstrual period, without measuring the L/S ratio if the fetal heart was heard at a time when the fundal height was 18 to 20 cm, if the gestational age at the same time calculated from the normal menstrual period was 18 to 20 weeks, or if fetal heart tones have been heard for 20 weeks with a fetoscope, and if the fetus is estimated by each of two experienced examiners to weigh as much as did the previous term infant, or more than 3000 g when the previous infant was preterm or growth retarded.
Delivery is postponed if there is discordance that implies a lower gestational age and there are no compelling reasons, maternal or fetal, to effect delivery before the onset of labor , such as previous vertical incision in the uterus or strong suspicion of retarded fetal growth. With this approach, about 60 percent of repeat cesarean sections have been performed at the Parkland Hospital at a scheduled time, and respiratory distress has not been a problem in those pregnancies terminated by schedules repeat cesarean section before the onset of labor.
For women with uncertain or unverified menstrual periods, and in whom early gestational dating by ultrasound was not performed, timing of delivery must be determined either by assuring pulmonary maturity with determination of the L/S ratio or by awaiting spontaneous labor. In modern obstetrical practice, there are virtually no contraindications to cesarean section. Cesarean section is seldom indicated, however, if the fetus is dead or premature to survive.
Exceptions to this generalization include pelvic contraction of such a degree that vaginal delivery by any means is impossible, most cases of placenta previa, and most cases of neglected transverse lie. Conversely, whenever the maternal coagulation mechanism is seriously impaired, delivery that minimizes incisions_-vaginal delivery—is preferable in most instances. There is no doubt that vaginal delivery most often will prove to be safe following a previous cesarean section.
Numerous reports have been established in the past few years that confirm the earlier reports by Rive and Teich, Douglas and co-workers that attest to the safety and efficacy of vaginal delivery in women who previously had cesarean sections. Flamm, in an excellent review, summarized results from 21 reports including his own. He reported that of 6,258 women who underwent a trail of labor, 5,356 were delivered vaginally (86 percent) and without a maternal mortality. There were five fetal losses and one uterine dehiscence of a previous vertical incision.
With an incidence of one maternal mortality per 1000 cesarean sections, this approach likely saved five mothers and apparently did not increase perinatal mortality. Vaginal delivery subsequent to a cesarean section can be safely carried out for women who have had one previous low-transverse uterine incision without an extension. Series have been published in which trials of labor were allowed in women with more than one cesarean section. In most of these reports, the outcomes have been good and the complications minimal.
In order to draw valid conclusions, more patients will have to be studied. If a trial of labor is planned for a woman with more than one previous cesarean section, the responsibility for assuring adequate medical and nursing personnel and technical support remains with the physician. At Parkland Hospital, they continue to limit a trial of labor to those women with a single previous low-transverse cesarean section documented by operative report not to have had an extension of the uterine incision. The indications of abdominal delivery are numerous and varied.
Their number and frequency have mounted as the safety of cesarean section for both mother and infant has increased in relation to traumatic methods of vaginal delivery. The operation must not be regarded as a panacea for all obstetrical difficulties and should not be performed only when indicated by sound obstetrical judgment. The individual indications are considered separately devotedly to the various problems of pregnancy and labor. The principal conditions for which cesarean section is performed are; contracted pelvis or cephalopelvic disproportion, in most cases of disproportion, contraction of the pelvic inlet is responsible.
In these a trial of labor is advisable before caesarean section is resorted to, since the clinical prognosis proves wrong in a certain proportion, even in the face of adverse radiologic measurements, and engagement of the head is followed by vaginal delivery. However, with breech presentations, cesarean section should be performed without a trial of labor if the pelvis is contracted and a likelihood of cephalopelvic disproportion exists. The second most frequent indication for caesarean section is myomectomy, or plastic operation on the uterus.
In such cases prophylactic cesarean section is often indicated to reduce the risk of uterine rupture in late pregnancy or labor. This problem is discussed in greater detail under the heading of rupture of the uterus. Other conditions in which continuation of pregnancy to term may result in greater risk of the fetus, such as diabetes, isoimmunization to the Rh or other blood factors, or a history of repeated deaths in the utero in the late pregnancy, others are placenta previa, placental abruption, uterine inertia, toxemia of pregnancy, fetal distress and fetal malpresentation.
Maternal tumors blocking the birth canal and other conditions in which expulsive efforts by the mother may be hazardous like intracranial aneurysm and brain tumor. Fetal tumor causing disproportion is an indication which is more theoretic than real, however; if the malformation is large enough to cause dystocia it is almost always incompatible with normal survival of the infant and craniotomy or embryotomy is preferable.
Abnormalities of the maternal soft tissues that render vaginal delivery hazardous like carcinoma of the cervix, extensive varices of the vagina, rectal stricture, previous vaginal plastic operation, or repaired vesicovaginal or rectovaginal fistula. Elderly primigravida or woman over age 35 is the management of patients having their first pregnancy toward the end of their reproductive years, especially after a long period of infertility, an increased premium is placed on the infant while less attention is given to the maternal risk in subsequent pregnancies.