In the womb 17
It’s the final act and the countdown is on. Although it’s impossible to tell exactly when the baby will be born, only 5% of babies are born on their due date, the rest can emerge any time within two weeks of their expected arrival. The mother’s kept guessing and waiting for signs, the first contraction of the uterus or the breaking water as the amniotic sac(囊) ruptures.
现在已经到了最后的时刻，让我们开始为孩子的出生倒数。孩子什么时候出生真的很难预测，只有5%的孩子在预产日当天出生，其他95%的孩子在预产日前后两周内任何时候都可能出生。母亲在等待着分娩信号的出现，也就是子宫的第一次收缩的出现，这时羊膜会破裂羊水流出来。
Nobody knows exactly what initiate labor(分娩), but it’s the baby’s lungs together with the placenta that determine the timing. When the lungs are mature, they secrete a protein into the amniotic fluid, which alters the placenta’s production of hormones. It slows the release of progesterone(黄体酮) and triggers the release of a new hormone, oxytocin(后叶荷尔蒙), which initiates the contractions of the uterine wall. Oxytocin also inhibits memory and may play a role in helping women to forget the pain of birth and bond with their new babies.
没有人知道是什么促使分娩的开始，不过孩子的肺和胎盘一起决定了分娩的时刻。当胎儿的肺成熟后，会向羊水里分泌出一种蛋白质，这就改变了胎盘所产生的荷尔蒙。胎盘会减少释放黄体酮，并释放出一种新的荷尔蒙，称为后叶荷尔蒙，这种荷尔蒙会引起子宫壁的收缩。后叶荷尔蒙也会抑制记忆，帮助妇女们忘记生产的痛苦，与孩子建立亲密联系。
During the first stage of labor, the baby’s head is locked in the bottom of the uterus, and is bearing down on the cervix(子宫颈), the barrier between the uterus and the vagina(阴道). The last thing to pass through the cervix was a tiny sperm 38 weeks ago. Now the cervix must stretch ten centimeters wide to allow the baby’s head, her largest part to pass through.
在分娩的第一个阶段，孩子的头位于子宫的底部，被慢慢挤向子宫与阴道之间的屏障—宫颈。38周前还是一个小小的精子现在已经是一个孩子，她要做的最后一件事就是通过宫颈。宫颈必须要扩大到十公分宽，这才可以让孩子的头和大部分身体通过。
For the mother, the pain of birth can be eased if she delivers standing up, sitting or squatting(蹲) rather than lying on her back. This can also speed up the first stage of labor and reduce the likelihood of needing medical intervention or a cesarean(剖腹产). Labor is also painful and stressful for the baby, the squashing(压碎) of the umbilical cord can easily constrict the supply of oxygen. To help the baby cope, her body release large quantities of adrenalin(肾上腺素) to keep her heart pumping fast enough. Adrenalin also helps prepare the lungs for the lifetime of work they’re about to begin.
对于母亲来说，如果她站着、坐着或者蹲着而不是躺着分娩的话，痛苦就会减轻。这样也能加速第一阶段分娩，降低使用药物干预或者采用剖腹产的可能性。生产对孩子来说也是痛苦而紧张的，因为脐带被挤压可能使氧气供应不足。为了帮助度过难关，孩子的身体会释放出大量的肾上腺素使心脏保持快速跳动。肾上腺素也帮助孩子的肺为即将开始的辛勤工作做好准备。
Once the cervix has fully opened, the second stage of labor, the actual delivery begins. With each contraction of the uterus, the baby is pushed further through the cervix and vagina until eventually her head is just visible. The contractions are only minutes apart now and after each one the midwife(助产士) encourages the mother to push down hard and helps squeeze the baby out. As soon as the baby is delivered, her lungs drain off fluid and air rushes in, expanding the air sacs that in an instant begin extracting oxygen to keep the baby alive.
