预产期到底是B超为准，还是根据最后一次月经？

52wangluo

３２周的时候照的B超说预产期比原先算得提早2周！这个到底以哪个为准？

linda@sydney

应该B超准吧，我的得晚两周呢

whuang

Early ultrsound (eg. 8-13 week)is accurate to determine the due day. The the date day should be determine in early pregnancy (by last period and early ultrasound measurement.   

Late ultrasound will be use to check for the growth of the baby.  If an ultrasound at 32 weeks shows the baby is of 34 weeks size, it is indicate a big baby.

However, if the 32 week ultrasound is the only scan for this pregnancy, the due day will be decided by scan with an error of ± 2 weeks.

52wangluo

谢谢楼上的JMs. 我在20周作的B超预产期比原先的提早1周，32周B超预产期比原先提早2周，那是不是就是说我的预产期应该以20周的B超为准？问题是现在医院还是以原先的根据月经算的为我的预产期。真担心要是宝宝不在due date之前出来的话，如果根据原先的预产期，那不是很糟糕？

breville

我的每次b超都推迟点儿，目前推迟了近2周

bearjoanne

我的GP说应该以第一次b超为准，越早越准。。。我8周做的，那时候看最准。用月经算有些人排卵早有些人排卵晚，受精卵大小就会不一样。。。越往后b超越难说明问题，因为有些胎儿长的快有的长的慢，像我20周的b超，上面都说我的预产期是某日期正负8天内。

whuang

As I mentioned previously, the due day should not be changed when it is decided in earlier pregnancy (unless there is error in calculation or ultrasound measurement).

If you periods are regular of 28 day cycle, the likelihood that the due day calculated from your period is the most accurate.  20 week scan can have error of ± 1 week to determine the due day(not all 20 week old babies have the same size) and 30+ weeks scan have error of ± 2 weeks (baby start to show more difference in sizes - eg. baby with birthweight of 3.2kg at full term will have a scan of 32 week size by ultrasound at this stage, for baby whose birthweight of 4kg at full term will have a size of that of 34 weeks at its 32 week ultrasound).  If the ultrasound at 20 weeks show your baby is one week in advance and at 32 weeks in two weeks advance - this means that you will have a big baby (e.g close to 4kg at 40 weeks if it keep growing at the same rate - make sure you do not have gestational diabetics.

For Breville, if your "due date" is later and later with each scan, your baby is small. Your baby need more monitoring and more scan to check growth etc. You doctor may suggest to deliver your baby earlier if scan show that your baby not growing, decrease liquor volume, or increase resistence in placenta circulation.

帅帅猪头饼

我的OB说第12周左右的那次b超最准

52wangluo

原帖由 whuang 于 2009-7-14 19:32 发表
As I mentioned previously, the due day should not be changed when it is decided in earlier pregnancy (unless there is error in calculation or ultrasound measurement).

If you periods are regular of  ...

非常感谢whuang.我有孕期糖尿diet control,今天35周去医院又照了一次B超，结果是due date by ultrasound和我根据月经算的竟然同一天，医生说宝宝的size是perfect。。。。头稍微大，但是医生说说明brain多........本来上次医生打算让我38周催生，现在说不用了.......我我我我现在很confused。。。。。
以前的两次B超（20周和32周是在同一个地方做的，不在医院做）都说预产期提前提前，为什么这次数值很好呢？都不知道该相信哪一个了。我现在担心的是如果真的是根据月经那天的预产期，在那之前宝宝不主动出来的话，会不会不好生？搞得我现在很郁闷........

whuang

A good ultrasound report at 30+ weeks, should not change your due day. It should give an estimate foetal weight (EFW) and its position at a centile chart. Eg: 50th centile is averay size (Aussuie size, a litter big for Chinese baby). Between 10th and 90th centile is "normal". However, a baby at 10th centil is small, and at 90th centile is big.  It is important to consider mother's size (height).  The report should also mentions about AFI (liquor volume) and S/D ratio (placental resistance) to indicate foetal well-being.