If this is accompanied by polyhydramnios, drain the mother’s amniotic sac slowly by draining her hindwaters with a Drew–Smythe catheter. Alternatively, rupture her forewaters by making a small hole with an amnion hook. Give her an escalating oxytocin IV (23.2), and she will probably deliver promptly.
If anencephaly is not accompanied by polyhydramnios (10%), pregnancy may rarely be prolonged up to a year or more, and make delivery difficult. Try PGE pessaries first (the ideal indication for them). Then try surgical induction and an escalating oxytocin IV (23.2). These will probably succeed. If you cannot induce labour (23.2), you will have to do a Caesarean section—this is tragic, so avoid it if you can.
If you make the diagnosis during pregnancy, induce labour, and try to avoid Caesarean section.
If you make the diagnosis when labour with a cephalic presentation has been in progress for some time, and the baby’s head is more than minimally enlarged, you will have to make it smaller before you can deliver him. If he is dead, drain his CSF with a lumbar puncture needle. Some obstetricians would do this even if he is alive (draining his CSF does not kill him), others would wait for his heart to stop. If you are not sure of the diagnosis, or don’t feel you can risk sacrificing him, you may be forced to do a Caesarean section.
To perforate his head, wait until dilatation has passed 3cm, then drain his cerebrospinal fluid with a large needle between his widely separated skull bones, or, less satisfactorily, with Simpson’s perforator. His collapsed head will slowly settle into his mother’s pelvis, and he will deliver.
CAUTION! If possible, perforate the baby’s head before the mother is 5 cm dilated, because her over-distended lower segment may rupture if you don’t.
If you make the diagnosis during a breech presentation, he will probably deliver spontaneously as far as his umbilicus (23.7). Progress will then be arrested as his hydrocephalic head fails to enter her pelvic brim. Draining his CSF will be less messy than a craniotomy: (1) If, at this stage you see the commonly-associated meningomyelocele, pass a steel or gum elastic male catheter through the spinal defect into his ventricles, to drain off his CSF. If he has no spina bifida, you can easily do a laminectomy with a scalpel, to allow the catheter to enter. Or, (2) pass a needle through his occipital bone into his skull. Or, (3) make sure that her bladder is empty, and then tap his aftercoming head abdominally with a large spinal needle.