昨晚看了這篇文章，預計今早要去照6W超音波的我，竟然凌晨六點被噩夢驚醒，夢到我6W的陰超只照到妊娠囊，沒照到卵黃囊... 嚇醒的時候整個人傷心欲絕~ 唉...下面這段話寫的真是貼切呀~ "從驗孕後的短暫喜悅，接踵而來的就是不間斷的擔心，擔心是否子宮外孕，是否順利著床，有沒有出血，會不會是空包彈..."

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 Source: 婦產科醫師～張建玫的部落格

懷孕初期前兩個月確實是難熬的時光，從驗孕後的短暫喜悅，接踵而來的就是不間斷的擔心，擔心是否子宮外孕，是否順利著床，有沒有出血，會不會是空包彈，直到大約第７、８週等著再照超音波，再等著醫師的宣判看看有胎囊內無心跳。

懷孕初期，１０位準媽媽當中有３～４個會有出血的情形，專有名詞叫『脅迫性流產』。這懷孕初期出血的孕婦當中，有一半能保住，一半真的流產。一般人說三個月以前最好不要說的原因，不是說了會流產；而是早期懷孕不穩定，出血的機率高，萬一不幸流產、或是空包彈、胎兒沒心跳，心裡已經不好受，如果發現懷孕時就已經昭告天下，發生不幸，後來朋友同事問起孕事，還得要解釋說懷孕不成功流產，這是二次傷害～

不過，也要在這裡提供數據給準備懷孕或剛懷孕的女生，以免懷孕初期擔心害怕，以致於請假在家每天臥床…並沒有那麼可怕

懷孕初期發生流產或空包彈，大部分發生在懷孕８週之前，８週以後的流產率逐漸降低。

驗尿發現有懷孕，我們會照超音波，如果：

子宮內已經有妊娠囊（就是一個圈圈），流產的機率11.2%，

妊娠囊裡還有一個卵黃囊（兩個圈圈），流產的機率8.5%，

看到胎兒，有5mm的長度，且有心跳，流產的機率7.2%，

看到胎兒，有6 -10mm的長度，有心跳，流產的機率3.2%，

看到胎兒，有 > 10mm的長度，有心跳，流產的機率0.2%，

所以懷孕三個月以後，流產的機率比較低的時候，再確定的告訴周遭親朋好友這喜事，比較穩妥！

那要不要更大一點再說？呵呵，更大就不用說了，用看的就知道了！懷孕三個月以後，子宮的高度就超過骨盆腔了，外觀上已經看得出來小腹微凸了！懷孕４個月子宮的高度大概在下腹部頂端和肚臍之間；五個月時，子宮的高度就剛好到肚臍了！

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Source: http://www.brooksidepress.org/Products/Military_OBGYN/Ultrasound/1st_trimester_ultrasound_scannin.htm

First trimester scanning is useful to identify abnormalities in the early development of a pregnancy, including miscarriage and ectopic pregnancy, and provides the most accurate dating of a pregnancy. 

Technique
First trimester scanning can be performed using either an abdominal approach or a vaginal approach. Abdominal scanning is performed with a full maternal bladder, provides a wider field of view, and provides the greatest depth of view. Vaginal scanning is best performed with the bladder empty, gives a much greater resolution with greater crispness of fine detail. In circumstances where both approaches are readily available, the greater detail provided by transvaginal scans usually outweighs other considerations, and is preferred.

The patient is scanned in the normal examination position (dorsal lithotomy) with her feet secure in stirrups and her perineum even with the end of the examination table. Place a small amount of ultrasonic coupling gel on the tip of the transvaginal transducer. Then cover the transducer with a condom. After lubricating the vaginal opening, gently insert the transducer into the vagina.

Visualize the longitudinal plane of the uterus (sagital section) and evaluate its' size. It can be measured from the cervix to the fundus, AP diameter, and width. Normal uterine volume is less than 100 cc (nulliparous patients) and less than 125 cc (multiparous patients). Identify (if present), the gestational sac, yolk sac, fetus (or fetuses), presence or absence of fetal movement and fetal heart beat. 

After the uterus is evaluated by sweeping up and down and side to side, the ovaries are identified and evaluated. This is most easily accomplished by first identifying the internal iliac vessels. The ovaries are usually located just anterior to the iliac vessels.

Document important views and measurements on film or electronically. Then document your findings in some written format.

Gestational Sac
The gestational sac is the earliest sonographic finding in pregnancy. The gestational sac appears as an echogenic (bright echoes) ring surrounding a sonolucent (clear) center. The gestational sac does not correspond to specific anatomic structures, but is an ultrasonic finding characteristic of early pregnancy. Ectopic pregnancies can also have a gestational sac identified with ultrasound, even though the pregnancy is not within the endometrial cavity. 

The gestational sac first appears at about 4 weeks gestational age, and grows at a rate of about 1 mm a day through the 9th week of pregnancy. 

Your ability to identify an early gestational sac will depend on many factors, including the capabilities of the ultrasound equipment, your approach (vaginal or abdominal), your experience, the orientation of the uterus (generally it is easier to see if the uterus is anteflexed or retroflexed), and the presence of such complicating factors as fibroid tumors of the uterus. While a gestational sac is sometimes seen as early as during the 4th week of gestation, it may not be seen until the end of the 5th week, when the serum HCG levels have risen to 1000-1500 mIU.

Gestational sac size may be determined by measuring the largest diameter, or the mean of three diameters. These differences rarely effect gestational age dating by more than a day or two.

Yolk Sac
As the pregnancy advances, the next structure to become visible to ultrasound is the yolk sac. This is a round, sonolucent structure with a bright rim. 

The yolk sac first appears during the fifth week of pregnancy and grows to be no larger than 6 mm. Yolk sacs larger than 6 mm are usually indicative of an abnormal pregnancy. Failure to identify (with transvaginal ultrasound) a yolk sac when the gestational sac has grown to 12 mm is also usually indicative of a failed pregnancy.

Yolk sacs that are moving within the gestational sac ("floating"), contain echogenic material (rather than sonolucent), or are gross misshapen are ominous findings for the pregnancy.

Fetal Heart Beat
Using endovaginal scanning, fetal cardiac activity is often seen even before a fetal cell mass can be identified. The fetal cardiac muscle begins its' rhythmic contractions, and that rhythmic motion can be seen along the edge of the yolk sac. Initially, the fetal cardiac motion has a slower rate (60-90 BPM), but cardiac rate increases as the fetus develops further. Thus, for these early pregnancies, the actual cardiac rate is less important that its presence or absence.

Sometimes, with normal pregnancies, the fetal heartbeat is not visible until a fetal pole of up to 4 mm in length is seen. Failure to identify fetal cardiac activity in a fetus whose overall length is greater than 4 mm is an ominous sign.

It can sometimes be difficult identifying a fetal heartbeat from the background movement and maternal pulsations. You may find it useful in these cases to scan with one hand while taking the maternal pulse with the other. This makes it easier to identify sonographic movements that are dyssynchronous with the maternal pulse.

Fetal Pole
A mass of fetal cells, separate from the yolk sac, first becomes apparent on transvaginal ultrasound just after the 6th week of gestation. This mass of cells is known as the fetal pole. It is the fetus in its somite stage. Usually you can identify rhythmic fetal cardiac movement within the fetal pole, although it may need to grow several mm before this is apparent.

The fetal pole grows at a rate of about 1 mm a day, starting at the 6th week of gestational age. Thus, a simple way to "date" an early pregnancy is to add the length of the fetus (in mm) to 6 weeks. Using this method, a fetal pole measuring 5 mm would have a gestational age of 6 weeks and 5 days.

Crown Rump Length
This term is borrowed from the early 20th century embryologists who found that preserved specimens of early miscarriages assumed a "sitting in the chair" posture in both formalin and alcohol. This posture made the measurement of head-to-toe length impossible. Instead, they subsituted the head-to-butt length (crown rump length) as a reproducible method of measuring the fetus.

Early ultrasonographers used this term (CRL) because early fetuses also adopted the sitting in the chair posture in early pregnancy. Today, the crown rump length is a universally recognized term, very useful for measuring early pregnancies. The CRL is highly reproducible and is the single most accurate measure of gestational age. After 12 weeks, the accuracy of CRL in predicting gestational age diminishes and is replaced by measurement of the fetal biparietal diameter. 

In at least some respects, the term "crown rump length" is misleading:

• For much of the first trimester, there is no fetal crown and no fetal rump to measure. 

• Until 53 days from the LMP, the most caudad portion of the fetal cell mass is the caudal neurospone, followed by the tail. Only after 53 days is the fetal rump the most caudal portion of the fetus.

• Until 60 days from the LMP, the most cephalad portion of the fetal cell mass is initially the rostral neurospore, and later the cervical flexure. After 60 days, the fetal head becomes the most cephalad portion of the fetal cell mass.

• What is really measured during this early development of the fetus is the longest fetal diameter.

From 6 weeks to 9 1/2 weeks gestational age, the fetal CRL grows at a rate of about 1 mm per day.

Determination of Gestational Age
Measurement of the gestational sac diameter or the length of the fetal pole (CRL) can be used to determine gestational age. Charts have been developed for this purpose, but some simple rules of thumb can also be effectively used.

• Gestational Sac: Gestational age = 4 weeks plus (mean sac diameter in mm x days). This relies on the growth of the normal gestational sac of 1 mm per day after the 4th week of gestation. For example, a gestational sac measuring 11 mm would be approximately 5 weeks and 4 days gestational age. (4 weeks plus 11 days = 5 weeks and 4 days).

• Crown Rump Length: Gestational age = 6 weeks plus (CRL x days). This relies on the growth of the normal fetus of 1 mm per day after the 6th week of gestation. For example, a CRL of 16 mm would correspond to a gestational age of 8 weeks and two days (6 weeks plus 16 days = 8 weeks and 2 days).

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Answer:

Doctors generally agree that the risk of miscarriage decreases once the pregnancy reaches a point that an ultrasound can detect a heartbeat. The exact amount that it decreases, however, seems to vary by group.

It's hard to say any exact numbers from the available research, but here are some statistics that certain studies have come up with.

For women with no vaginal bleeding, most estimates suggest that the odds or having a miscarriage after seeing a heartbeat are about 4%.

For women with vaginal bleeding but also a detected heartbeat on ultrasound, risk of miscarriage is about 13% according to one study.

One study found that about 17% of women with a history of recurrent miscarriages will miscarry after seeing a heartbeat on the ultrasound.

Mothers over 35 also face significant miscarriage risk after ultrasound detects a heartbeat, even though the risk does drop after detecting the heartbeat. A 1996 study found that women over 36 have a 16% risk of miscarriage at this point, and women over 40 have a 20% risk.

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Do Infertile Women Have Higher Miscarriage Rates?

Source: http://www.wdxcyber.com/ninfer03.html

Frederick R. Jelovsek

Women undergoing infertility evaluation and treatment are concerned not only with getting pregnant, but also with whether they will carry that pregnancy to get a healthy baby. Miscarriage in the general population ranges from 10-20% but many of those miscarriages occur before the women knows she is pregnant and they just present as heavy menstrual periods. The miscarriage rate of clinically recognized pregnancies is about 8%.

Many pregnancies that are going to result in miscarriage (spontaneous abortion) never develop to the point where there is a heartbeat detectable by vaginal ultrasound. In fact recent studies have suggested that if a fetal heart beat is detected by ultrasound between 6 and 9 weeks of menstrual age (4-7 weeks after ovulation), then the chance of subsequent miscarriage is only about 2%. Physicians use this 2% number to reassure women who have had an ultrasound in which the baby's heart beat was seen.

Keenan and coworkers looked at this data in women undergoing infertility work ups to see if they have the same low miscarriage rate after fetal heart beat detection as do women who do not have infertility problems. Keenan JA, Rizvi S, Caudle MR: Fetal loss after detection of heart motion in infertility patients; Prognostic factors. J Reprod Med 2998;43:199- 202. In this study, they followed 231 women who were seen in their infertility clinic and who had fetal heart beats detected 28-38 days after ovulation by ultrasound.

They found that the incidence of miscarriage was:

Patients who have infertility problems have mixed medical reasons for their infertility. They also tend to be older because they may have put off getting pregnant for various reasons. They appear to have much higher miscarriage rates than the general population, especially if they are over 35 years of age or if they have a multiple pregnancy. It is important that we are able to tell women what to expect under various conditions.

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Source: http://www.fertilityties.com/post/show/miscarriage-rates

This is a really great question healthyjen...for the most part, I would hold off saying anything until an ultrasound is done 8wks into a pregnancy or beyond. If a fetal heart beat is noted then, you're pretty much in the clear, with only a standard 2-3% miscarriage rate at that time.

Here are some of those rates again as an approximation, and miscarriage rates are dependent on age as they increase signficantly after the age of 37.

positive hpt 10-15%

fetal heart activity at 6 wks 6-8%

fetal heart activity at 8 wks 2-3%

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Source: http://www.babyhome.com.tw/note.php?mid=124677&op=dt&lno=82628627&no=4721819

孕期超音波指標對照表及說明

*** 一、參考資料 ***

孕期通過超音波判斷胎兒的發育的大小是較有參考價值的一種方法，孕婦在做超音波的時候會看到檢查報告上有一些數值，這些數值就是告訴你寶寶的發育大小。

*** 二、孕早期胎兒發育的過程及超音波所見 ***

妊娠是一個複雜的過程，卵子受精後，進入宮腔，胚胎及附屬物迅速生長發育直至成熟的過程中，每個孕周都會有不同的變化。

♡ 4周 ♡ 胎兒只有 0.2 厘米(cm)。
受精卵剛完成著床，羊膜腔才形成，體積很小。超聲還看不清妊娠跡象。

♡ 5周 ♡ 胎兒長到 0.4 厘米。
進入了胚胎期，羊膜腔擴大，原始心血管出現，可有搏動。超音波可看見小胎囊，胎囊約占宮腔不到1/4，或可見胎芽。

♡ 6周 ♡ 胎兒長到 0.85厘米。
胎兒頭部、腦泡、額面器官、呼吸、消化、神經等器官分化，超音波胎囊清晰可見，並見胎芽及胎心跳。

♡ 7周 ♡ 胎兒長到 1.33 厘米。
胚胎已具有人雛形，體節已全部分化，四肢分出，各系統進一步發育。超音波清楚看到胎芽及胎心跳，胎囊約占宮腔的 1/3。

♡ 8周 ♡ 胎兒長到 1.66 厘米。
胎形已定，可分出胎頭、體及四肢，胎頭大于軀幹。超音波可見胎囊約占官腔 1/2，胎兒形態及胎動清楚可見，並可看見卵黃囊。

♡ 9周 ♡ 胎兒長到 2.15 厘米。
胎兒頭大于胎體，各部表現更清晰，頭顱開始鈣化、胎盤開始發育。超音波可見胎囊幾乎占滿宮腔，胎兒輪廓更清晰，胎盤開始出現。

♡ 10周 ♡ 胎兒長到 2.83 厘米。
胎兒各器官均已形成，胎盤雛形形成。超音波可見胎囊開始消失，月芽形胎盤可見，胎兒活躍在羊水中 。

♡ 11周 ♡ 胎兒長到 3.62 厘米。
胎兒各器官進一步發育，胎盤發育。超音波可見胎囊完全消失，胎盤清晰可見。

♡ 12周 ♡ 胎兒長到 4.58 厘米。
外生殖器初步發育，如有畸形可以表現，頭顱鈣化更趨完善。顱骨光環清楚，可測雙頂徑，明顯的畸形可以診斷，此後各髒器趨向完善。

*** 三、孕中期超音波檢查胎兒發育的正常值 ***

孕期通過超音波判斷胎兒的發育的大小是較有參考價值的一種方法，孕婦在做超音波的時候會看到檢查報告上有一些數值，這些數值就是告訴你寶寶的發育大小。

♡ 孕13周 ♡
雙頂徑的平均值 = 2.52 士 0.25
腹圍的平均值 = 6.90 士 1.65
股骨長 = 1.17 士 0.31

♡ 孕14周 ♡
雙頂徑的平均值 = 2.83 士 0.57
腹圍的平均值 = 7.77 士 1.82
股骨長 = 1.38 士 0.48

♡ 孕15周 ♡
雙頂徑的平均值 = 3.23 士 0.51
腹圍的平均值 = 9.13 士 1.56
股骨長 = 1.74 士 0.58

♡ 孕16周 ♡
雙頂徑的平均值 = 3.62 士 0.58
腹圍的平均值 = 10.32 士 1.92
股骨長 = 2.10 士 0.51

♡ 孕17周 ♡
雙頂徑的平均值 = 3.97 士 0.44
腹圍的平均值 = 11.49 士 1.62
股骨長 = 2.52 士 0.44

♡ 孕18周 ♡
雙頂徑的平均值 = 4.25 士 0.53
腹圍的平均值 = 12.41 士 1.89
股骨長 = 2.71 士 0.46

♡ 孕19周 ♡
雙頂徑的平均值 = 4.52 士 0.53
腹圍的平均值 = 13.59 士 2.30
股骨長 = 3.03 士 0.50

♡ 孕20周 ♡
雙頂徑的平均值 = 4.88 士 0.58
腹圍的平均值 = 14.80 士 1.89
股骨長 = 3.35 士 0.47

♡ 孕21周 ♡
雙頂徑的平均值 = 5.22 士 0.42
腹圍的平均值 = 15.62 士 1.84
股骨長 = 3.64 士 0.40

♡ 孕22周 ♡
雙頂徑的平均值 = 5.45 士 0.57
腹圍的平均值 = 16.70 士 2.23
股骨長 = 3.82 士 0.47

♡ 孕23周 ♡
雙頂徑的平均值 = 5.80 士 0.44
腹圍的平均值 = 17.90 士 1.85
股骨長 = 4.21 士 0.41

♡ 孕24周 ♡
雙頂徑的平均值 = 6.05 士 0.50
腹圍的平均值 = 18.74 士 2.23
股骨長 = 4.36 士 0.51

♡ 孕25周 ♡
雙頂徑的平均值 = 6.39 士 0.70
腹圍的平均值 = 19.64 士 2.20
股骨長 = 4.65 士 0.42

♡ 孕26周 ♡
雙頂徑的平均值 = 6.68 士 0.61
腹圍的平均值 = 21.62 士 2.30
股骨長 = 4.87 士 0.41

♡ 孕27周 ♡
雙頂徑的平均值 = 6.98 士 0.57
腹圍的平均值 = 21.81 士 2.12
股骨長 = 5.10 士 0.41

♡ 孕28周 ♡
雙頂徑的平均值 = 7.24 士 0.65
腹圍的平均值 = 22.86 士 2.41
股骨長 = 5.35 士 0.55

*** 四、孕晚期超音波檢查胎兒發育的正常值 ***

♡ 孕29周 ♡
雙頂徑的平均值 = 7.50 士 0.65
腹圍的平均值 = 23.71 士 1.50
股骨長的平均值 = 5.61 士 0.44

♡ 孕30周 ♡
雙頂徑的平均值 = 7.83 士 0.62
腹圍的平均值 = 24.88 士 2.03
股骨長的平均值 = 5.77 士 0.47

♡ 孕31周 ♡
雙頂徑的平均值 = 8.06 士 0.60
腹圍的平均值 = 25.78 士 2.32
股骨長的平均值 = 6.03 士 0.38

♡ 孕32周 ♡
雙頂徑的平均值 = 8.17 士 0.65
腹圍的平均值 = 26.20 士 2.33
股骨長的平均值 = 6.43 士 0.49

♡ 孕33周 ♡
雙頂徑的平均值 = 8.50 士 0.47
腹圍的平均值 = 27.78 士 2.30
股骨長的平均值 = 6.42 士 0.46

♡ 孕34周 ♡
雙頂徑的平均值 = 8.61 士 0.63
腹圍的平均值 = 27.99 士 2.55
股骨長的平均值 = 6.62 士 0.43

♡ 孕35周 ♡
雙頂徑的平均值 = 8.70 士 0.55
腹圍的平均值 = 28.74 士 2.88
股骨長的平均值 = 6.71 士 0.45

♡ 孕36周 ♡
雙頂徑的平均值 = 8.81 士 0.57
腹圍的平均值 = 29.44 士 2.83
股骨長的平均值 = 6.95 士 0.47

♡ 孕37周 ♡
雙頂徑的平均值 = 9.00 士 0.63
腹圍的平均值 = 30.14 士 2.17
股骨長的平均值 = 7.10 士 0.52

♡ 孕38周 ♡
雙頂徑的平均值 = 9.08 士 0.59
腹圍的平均值 = 30.63 士 2.83
股骨長的平均值 = 7.20 士 0.43

♡ 孕39周 ♡
雙頂徑的平均值 = 9.21 士 0.59
腹圍的平均值 = 31.34 士 3.12
股骨長的平均值 = 7.34 士 0.53

♡ 孕40周 ♡
雙頂徑的平均值 = 9.28 士 0.50
腹圍的平均值 = 31.49 士 2.79
股骨長的平均值 = 7.4 士 0.53

*** 五、怎樣看孕期超音波檢查單 ***

懷孕期間，孕婦將做2-3次的超音波檢查，你是不是特別想知道報告單上的各種數字都說明了什麼？醫院超聲檢查報告單一般包括以下幾方面內容：胎囊、胎頭、胎心、胎動、胎盤、股骨、羊水和脊柱。它們各說明什麼問題，什麼情況下正常，而什麼情況下又屬異常呢？這裏提供一些參考指標：

1、胎囊：
胎囊只在懷孕早期見到。它的大小，在孕1.5個月時直徑約2厘米，2.5個月時約5厘米為正常。胎囊位置在子宮的宮底、前壁、後壁、上部、中部都屬正常；形態圓形、橢圓形、清晰爲正常；如胎囊為不規則形、模糊，且位置在下部，孕婦同時有腹痛或陰道流血時，可能要流產。

2、胎頭：
輪廓完整為正常，缺損、變形為異常，腦中線無移位和無腦積水為正常。BPD代表胎頭雙頂徑，懷孕到足月時應達到 9.3 厘米或以上。按一般規律，在孕 5 個月以後，基本與懷孕月份相符，也就是說，妊娠28 周（7 個月）時BPD約為 7.0 厘米，孕 32 周（ 8 個月）時約為 8.0 厘米，以此類推。孕8個月以後，平均每周增長約為 0.2 厘米為正常。

3、胎心
有、強為正常，無、弱為異常。胎心頻率正常爲每分鐘 120-160 次之間。

4、胎動
有、強為正常，無、弱可能胎兒在睡眠中，也可能為異常情況，要結合其他項目綜合分析。

5、胎盤
位置是說明胎盤在子宮壁的位置；胎盤的正常厚度應在 2.5-5 厘米之間；鈣化一項報告單上分為 Ⅲ 級 ~
Ⅰ級為胎盤成熟的早期階段，回聲均勻，在懷30-32周可見到此種變化；
Ⅱ級表示胎盤接近成熟；
Ⅲ級提示胎盤已經成熟。越接近足月，胎盤越成熟，回聲的不均勻。

6、股骨長度
是胎兒大腿骨的長度，它的正常值與相應的懷孕月份的 BPD 值差2-3厘米左右，比如說BPD為 9.3 厘米，股骨長度應為 7.3 厘米；BPD為8.9 厘米，股骨長度應為 6.9 厘米等。

7、羊水
羊水深度在 3-7 厘米之間為正常，超過7厘米為羊水增多，少于3厘米為羊水減少。

8、脊椎
胎兒脊柱連續為正常，缺損爲異常，可能脊柱有畸形。

9、臍帶
正常情況下，臍帶應漂浮在羊水中，如在胎兒頸部見到臍帶影像，可能為臍帶繞頸。

10、術語縮寫

BPD: 雙頂徑 (頭骨橫徑)
TCD: 小腦橫徑
HC: 頭圍
AC: 腹圍
FL: 股骨徑 (大腿骨的長度)
FTH: 胎兒腿部皮下脂肪厚度
CRL: 頭頂到臀部的距離
TTD: 腹部的橫徑
APTD: 腹部的前後徑
EFBW: 預估胎兒的體重
AFI: 羊水指數
MVP: 最大垂直羊水池
FHB: 胎心音
FTA: 超音波預估胎兒的週數
DGA: 依最後一次月經計算的胎兒週數
FUH: 宮高
FSD: 子宮底到恥骨聯合上緣的距離，
(一般來說長度的公分數就等於胎兒的週數。例 FSD=24cm﹐胎兒大約是 24 週。)

11、胎位縮寫

胎位為先露部的代表在產婦骨盆的位置，亦即在骨盆的四相位--左前、右前、左後、右後。

頂先露的代表骨為枕骨 (occipital，縮寫為O)；
臀先露的代表骨為薦骨(sacrum，縮寫為S)；
面先露的為下頦骨(mentum，縮寫為M)；
肩先露的代表骨為肩胛骨(scapula，縮寫為Sc)。

胎位的寫法由三方面來表明：

1)、代表骨在骨盆的左側或右側，簡寫為左 (L) 或右 (R)；
2)、代表骨名稱，如頂先露為 “枕”，即 “O”，臀先露為“薦”，即“S”，面先露為“頦”，即“M”，肩先露為 “肩”，即“Sc”；
3)、代表骨在骨盆之前、後或橫。例如頂先露，枕骨在骨盆左側，朝前，則胎位爲左枕前(LOA)，為最常見之胎位。

各胎位縮寫如下：

頂先露有六種胎位：
左枕前(LOA)
左枕橫(LOT)
左枕後(LOP)
右枕前(ROA)
右枕橫(ROT)
右枕後(ROP)

臀先露有六種胎位：
左骶前(LSA)
左骶橫(LST)
左骶後(LSP)
右骶前(RSA)
右骶橫(RST)
右骶後(RSP)

面先露有六種胎位：
左頦前(LMA)
左頦橫(LMT)
左頦後(LMP)
右頦前(RMA)
右頦橫(RMT)
右頦後(RMP)

肩先露有四種胎位：
左肩前(LScA)
左肩後(LScP)
右肩前(RScA)
右肩後(RScP)

=========================================

資料來源: http://www.books.com.tw/magazine/item/babymother/babymother0715.htm

※懷孕一個月（1~4週）
**胎兒成長

我還不成人形喔
1. 此時受精卵才剛著床受孕超音波還看不到子宮內有任何胚囊的影像。
2. 胎盤功能尚不成熟，從此時到懷孕三個月止，是流產風險較高的時期。

**孕媽咪的變化
子宮大小：如雞蛋般
羊水量：約10㏄

1. 乳頭顏色變黑變深，有些孕婦乳頭變得較敏感。
2. 容易疲倦
3. 飲食的習慣可能改變，如喜歡吃甜食，或是口味改變等。

胎兒成長與孕媽咪的變化
陳樹基醫師表示，每個胎兒每個月的重量差別很大，因此沒有所謂絕對正常的重量。胎兒的重量與胎兒吸收的營養、胎盤功能好壞、本身體質、母親健康情形有關， 因此文章中提供的胎兒重量或大小是一般胎兒的平均值，供準爸媽們參考。

同樣地，懷孕的女性產生的身體變化會因每個人的體質不同而有些微差異。

預產期怎麼算？
1. 以最後一次月經的第一天加上280天或將日期減三加七。
國泰醫師表示，將最後一次月經來的第一天加上280天，就是嬰兒可能出生的日期。馬偕婦產科主治醫師徐金源表示，只要將最後一次月經來的第一天日期，把月 份減三，日期加七就是預產期，例如最後一次月經來的日期是七月一日，那麼預產期約為來年的四月八日。

2. 胎兒頭臀徑+6.5=胎兒週數(特殊設計)。
由於部分孕媽咪的月經日期不固定，徐金源醫師表示，可在前三個月(8-12週)時，測量胎兒頭頂到屁股的距離(頭臀徑)，並將此距離(公分)加上 6.5(一個常數)就等於胎兒的週數，例，頭臀圍為1公分，則胎兒的週數約為七週半。這個公式只適用於前三個月，若超過四個月的話，則以胎兒的頭圍、腹圍 來得知胎兒大小，因為三、四個月之後，胎兒大小會受到吸收到的營養、遺傳等因素所影響，因此預產期仍以懷孕初期推算出來的日期最準。

葉酸、魚油幫助胎兒腦部發育
原則上，孕媽咪應盡量從食物中攝取均衡的營養，以供胎兒生長所需的養分，這些養分包括優質的蛋白質、鈣、鐵與各類維生素等。醫師表示若能從食物中補充鐵質的話，就不需要另外服用鐵劑，因為鐵質服用過多的話，容易造成便秘。

徐 金源醫師表示，葉酸是胎兒在生長初期不可少的營養素，如果缺乏的話，很可能導致胎兒神經管缺陷，造成如胎兒無腦症。因此，一般孕婦從懷孕前一個月到懷孕的 第三個月止，必須每天補充0.4mg的葉酸，而高危險群的孕婦，也就是曾經生過神經管有缺陷的嬰兒，或是流產過的孕婦，補充劑量必須較一般孕婦高，每天約 為4mg，如此一來，可降低產出無腦症嬰兒的機率。目前市面上均有販授葉酸製劑，若孕媽咪無法接受吃藥的話，可從食物中攝取。另外，孕婦應在懷孕初期到 29週多攝取含有魚油DHA的食物，幫助胎兒的腦部發育。

孕媽咪的運動量
徐 金源醫師表示，孕媽咪可在懷孕期間可進行簡單的運動，如散步，並避免跑或跳等劇烈的運動。至於介於兩著間的運動，則需視個人體力即平常的活動量而有不同。 懷孕前就有爬山、游泳等運動習慣的孕媽咪，在懷孕初期及中期仍可以持續進行，但第八個月之後則應盡量避免，以防羊水破掉或是感染。

懷孕後期避免性活動
在性愛活動上，一般而言，若沒有出血或腹痛現象，只要避免壓迫到肚子，在懷孕初期及中期仍可維持性生活，徐金源醫師建議在進行時，要戴著保險套，因為精子中的前列腺素可能導致子宮收縮。在後期三個月應避免性活動，因為容易造成子宮收縮或破水。

※懷孕2個月（5~8週）
**胎兒成長
胚囊直徑：約2-2.5公分
胚囊重量：約4公克

我開始像點人樣了
1. 此時尚在胚胎期。胚胎在胎囊中，泡在羊水裡，胎盤與臍帶開始發展成形，胚胎開始與母體相連。
2. 第五週開始進入器官形成期，到第八週為止四肢發育完成。
3. 頭部器官如眼、耳、鼻、口已有初步外形。

我的心撲通撲通跳
4. 生成血管，血液循環功能開始運作，並有心跳。
5. 具備腦部、脊椎與神經系統雛形。

**孕媽咪的變化
子宮大小：約10公分
羊水量：約20㏄

1. 乳房腫脹
2. 有些孕媽咪出現害喜現象
3. 膚質會因荷爾蒙改變產生變化，頭髮長的很快、指甲易折斷、牙齦浮腫、刷牙時易出血、容易流汗。
4. 子宮開始壓迫膀胱與直腸
5. 陰道分泌物增加

======================================

資料來源: http://www.obstetrics.com.tw/knowledge-5.htm

超音波在產科上的應用已有四、五十年，隨著超音波性能的提昇與醫學的進步，超音波應用的範圍也愈來愈廣泛，使用時機也較以往更為頻繁。雖然超音波的 安全性無虞，有沒有需要每次門診都做超音波檢查呢？也許瞭解一下不同週數時超音波檢查在醫學上的目的，可以?助我們做為取捨的依據。
（註：週數是指月經週數，從月經第一天開始計算，每七天算一週。第二百八十天就是預產期，即第四十週。）
1. 懷孕5~6週：胚胎是否著床在子宮內？有沒有子宮外孕？
　　 通常排卵發生在月經第十四天，受孕後受精卵發育成為囊胚，並在第二十天左右著床在子宮內膜，此時驗尿還不會呈陽性反應，只能由驗血（測血中β-hCG濃 度）看出是否懷孕。直到月經過期大約三天，大部份的驗孕試劑會呈現陽性反應。此時（懷孕四週又三天）藉由陰道超音波在子宮腔內已可見到小小的胚囊，到了五 週又四天若由腹部超音波仍看不到胚囊，就可能是子宮外孕或是過期流產，此時可測血中β-hCG濃度來幫助鑑別診斷。現在利用陰道超音波檢查有無子宮旁腫 塊，能夠在懷孕早期診斷子宮外孕，即可避免因破裂出血造成腹痛甚至休克等症狀。

2. 懷孕6~7週：胚胎是否正常發育？有沒有心跳？
　　 五週結束時在卵黃囊附近有時可以看到胚胎心跳，每分鐘大約一百次。胚胎六週時身長已有４～８mm，心跳大約一百三十次。正常胚胎發育可以見到以下里程碑： （1）胚囊平均直徑達１０ mm時就應看到卵黃囊（2）胚囊平均直徑達１８ mm時必須看到胚胎（3）胚胎身長超過５ mm就一定要有心跳。現在用超音波（尤其是陰道超音波）檢查可以判斷胚胎是正常發育或已胎死腹中，若是確定胎死腹中，及早加以治療，可以避免因自然流產造 成的出血、腹痛或感染等併發症。　

3. 懷孕6~9週：判斷單胞胎或多胞胎？單絨毛膜或雙絨毛膜？
　　 多胞胎屬於高危險妊娠，比起單胞胎出狀況的機率高出不少，例如雙胞胎出現胎兒異常的機率是單胞胎的二至三倍，雙胞胎早產的機率也比單胞胎高出四、五偣，所 以判斷單胞胎或多胞胎妊娠相當重要。雙胞胎本身還會因屬於單絨毛膜或雙絨毛膜而有不同命運。單絨毛膜雙胞胎出現雙胞胎輸血症候群（Twin-twin transfusion syndrome）的機率比雙絨毛膜雙胞胎高出許多，使得周產期死亡率增加三至四倍。用超音波區分雙胞胎是單絨毛膜或雙絨毛膜，最好的時機是在６～９週 時，到了懷孕中期（高層次超音波通常安排在２２週左右）超音波就很不容易來區分了。

4.懷孕9~11週：測量胎兒大小以判斷預產期是否正確？
　　 有些孕婦因為月經周期不是十分規則，造成受孕週數和月經週數有很大的差距，此時必須調整預產期以符合實際週數，以免無法判斷胎兒是否生長過度或生長遲滯， 或是無法判斷胎兒有沒有早產或是妊娠過期的情形。懷孕９～１１週時測量胎兒大小相當容易，誤差也比較小，十分適合做為判斷懷孕週數的依據。

5. 懷孕11~14週：測量頸部透明帶做初期唐氏症篩檢並可診斷重大先天畸型
　　　 懷孕十一至十四週藉著測量胎兒頸部透明帶，配合母血中 free β-hCG 和 PAPP-A 的濃度，即可計算胎兒唐氏症機率，此即初期唐氏症篩檢，檢出率接近九成，近年來日漸普及，是一種相當不錯的唐氏症篩檢方法。隨著超音波解析度的提高，我們 在懷孕十一至十四週時也能對胎兒的構造進行比較詳細的掃描，所以在測量胎兒頸部透明帶的同時，也可嘗試診斷胎兒先天畸型，有機會提早發現一些重大胎兒異常 （如無腦兒、四肢缺損等），此為超音波在懷孕初期的重要貢獻之一。