It is not permissible for pregnant and breastfeeding women to break the fast unless they fear for themselves or their children
Question

                I read a hadeeth in which the Prophet (peace and blessings of Allaah be upon him) said: “Allaah has waived the fast for pregnant and breastfeeding women.” Does that mean that fasting is not obligatory for them whether it entails hardship or not?.
Praise be to Allah.This hadeeth was 
      narrated by Abu Dawood, 2408; al-Tirmidhi, 715; al-Nasaa’i, 2315; and Ibn 
      Maajah, 1667. It says that the Prophet  (peace and blessings of Allaah 
      be upon him) said: “Allaah has relieved the traveller of half of the 
      prayer and of the duty to fast, and He has relieved pregnant and nursing 
      mothers (of the duty to fast).” It was classed as saheeh by al-Albaani in
      Saheeh Abi Dawood. 
This hadeeth is general 
    in meaning and applies to every pregnant woman, but the scholars limited it 
    to cases of hardship, based on the reason for which this ruling – namely 
    pregnant women not fasting – was prescribed. 
This is similar to the 
    reference to the sick in the verse (interpretation of the meaning): 
“and whoever is ill or 
    on a journey, the same number [of days which one did not observe Sawm 
    (fasts) must be made up] from other days”
[al-Baqarah 2:185]
This applies to everyone 
    who is sick, no matter how mild his illness. Some of the salaf, such as 
    ‘Ata’, applied it in general terms, and this was the view favoured by 
    al-Bukhaari. But the scholars, including the four Imams, rejected that 
    general application and restricted it to cases of sickness where fasting 
    causes hardship, based on the reason for which the ruling of not fasting was 
    prescribed. 
There are texts narrated 
    from the scholars which state this restriction; indeed it was narrated that 
    there was unanimous agreement among the scholars on this point, as we shall 
    see below.
 1 – Narrations from the 
    salaf 
Abu Dawood (2318) 
    narrated that Ibn ‘Abbaas said, concerning the verse “And as for those 
    who can fast with difficulty, (e.g. an old man), they have (a choice either 
    to fast or) to feed a Miskeen (poor person) (for every day)” [al-Baqarah 
    2:184]: This is a concession granted to old men and old women who are 
    able to fast, allowing them to break the fast and to feed one poor person 
    each day instead of fasting. (And this concession is also granted to) 
    pregnant and breastfeeding women, if they fear (harm). Al-Nawawi said: Its 
    isnaad is hasan. 
So here Ibn ‘Abbaas 
    restricted the concession granted to pregnant and breastfeeding women to 
    cases where they feared harm, whether the harm was to themselves or to their 
    children. 
Al-Shaafa’i narrated in
    al-Umm: Maalik told us, narrating from Naafi’, that Ibn ‘Umar was 
    asked about a pregnant woman, if she fears for her child. He said: She 
    should not fast, and she should feed one poor person for each day, giving a 
    mudd of wheat. 
Imam al-Bukhaari said: 
Chapter on the words, 
    “Exempt days”… al-Hasan and Ibraaheem said concerning breastfeeding or 
    pregnant women: If they fear for themselves or their children, they should 
    break the fast then make it up. End quote. 
This restriction of the 
    ruling was narrated from Ibn ‘Abbaas, Ibn ‘Umar, al-Hasan and al-Nakha’i 
    among the salaf. 
2 – The madhhabs of the 
    four imams. 
They were also agreed 
    upon this restriction of the ruling. 

    (i)The Hanafi madhhab
Al-Jassaas said in 
    Ahkaam al-Qur’aan, 1/244, after quoting the words of the Prophet  
    (peace and blessings of Allaah be upon him): “Allaah has relieved the 
    traveller of half of the prayer and of the duty to fast, and He has relieved 
    pregnant and nursing mothers (of the duty to fast).”: 
It is known that this 
    concession – granted to pregnant and breastfeeding women – is limited to 
    cases where they fear for themselves or for their children. 
He also said (1/252): 
Either pregnant and 
    breastfeeding women will themselves be harmed by fasting or their children 
    will be harmed. In either case, not fasting is better for them and fasting 
    is not allowed in their case. If fasting will not harm them or their 
    children, then they have to fast and it is not permissible for them to break 
    the fast. 
It says in al-Bahr 
    al-Raa’iq (2/308): 
If pregnant and 
    breastfeeding women fear for themselves or their children, they may are 
    allowed to break the fast in order to ward off any hardship. 
i.e., they may break the 
    fast so as to ward off harm… but this is restricted to cases of fear, i.e., 
    when they think that is most likely to happen… because if they do not fear 
    harm there is no concession granted to them. 

    (ii)The Maaliki madhhab
It says in Sharh 
    Mukhtasar Khaleel (2/262): 
If a pregnant woman fears 
    that her child may die, or be severely harmed, then she must break her fast. 
    If she fears that sickness may happen, it is permissible for her to break 
    her fast according to the correct view. And it was said that she must break 
    her fast if she fears sickness. The same applies to the breastfeeding woman, 
    if she fears that her child may die or be severely harmed, she must break 
    her fast, and if she fears sickness, it is permissible for her to break her 
    fast. This is subject to the condition that her child will not accept the 
    breast of any other woman, otherwise she is obliged to fast, 

    (iii)The Shaafa’i madhhab
Imam al-Shaafa’i said in
    al-Umm: 
If a pregnant woman fears 
    for her child, she should break her fast. The same applies if a 
    breastfeeding woman fears that her milk supply will be adversely affected. 
    But if that is bearable then she should not break her fast. The fast may 
    reduce the breast milk but it may be a bearable reduction, but if it is 
    extreme, then she should break her fast. 
Al-Nawawi said in 
    al-Majmoo’ (6/274):  
Our companions said: If 
    pregnant and breastfeeding women fear that fasting may harm them, they 
    should break the fast and make it up later on, and they do not have to offer 
    any fidyah, as in the case of one who is sick. There is no difference of 
    opinion on any of that. If they fear for themselves and their children, the 
    same applies and there is no difference of opinion. This was stated by 
    al-Daarimi, al-Sarkhasi and others. If they fear for their children but not 
    for themselves, they should break the fast and make it up later on, and 
    there is no difference of opinion on that… 

    (iv)The Hanbali madhhab
Ibn Muflih said in 
    al-Furoo’ (3/35): 
It is makrooh for 
    pregnant and breastfeeding women to fast if there is the fear that they or 
    their children may be harmed. 
Ibn ‘Aqeel said that if a 
    pregnant or breastfeeding woman fears for the pregnancy or the nursing 
    infant, it is not permissible to fast, and she must offer the fidyah. If 
    there is no such fear then it is not permissible for her not to fast. 
Shaykh al-Islam Ibn 
    Taymiyyah said in Majmoo’ al-Fataawa (25/218): 
If a pregnant woman fears 
    for her foetus, she may break the fast…  

    (v)The Zaahiri madhhab
Ibn Hazm said in 
    al-Muhalla (4/411): 
The fast is addressed to 
    pregnant and breastfeeding woman and old men. The Ramadaan fast is 
    obligatory for all of them, but if a breastfeeding woman fears that she may 
    have too little milk for her child and there is no one else to feed the 
    child, or if he will not take the breast of any other woman, or if a 
    pregnant woman fears for her foetus, or if an old man is unable to fast 
    because of his age, then they may break the fast… end quote. 
It says in 
    al-Mawsoo’ah al-Fiqhiyyah (28/55): 
The fuqaha’ are agreed 
    that pregnant and breastfeeding women may break the fast in Ramadaan, so 
    long as they fear sickness or an increase in sickness for themselves or 
    their children, or they fear harm or death. In the case of a pregnant woman, 
    the foetus is regarded as part of her body, so the fear for him is like the 
    fear of damage to any of her limbs or physical faculties. 
Al-Shawkaani said in 
    Nayl al-Awtaar (4/273), commenting on the hadeeth which says that 
    pregnant and breastfeeding women are allowed not to fast: 
This hadeeth indicates 
    that it is permissible for pregnant and breastfeeding women not to fast. 
    This was the view of the fuqaha’, if a breastfeeding woman fears for her 
    nursing infant or if a pregnant woman fears for the unborn child. They said: 
    They may definitely break the fast. End quote. 
It says in Fataawa 
    al-Lajnah al-Daa’imah (10/226): 
With regard to the 
    pregnant woman, she must fast whilst pregnant, unless she fears that fasting 
    may harm her or her unborn child, in which case she is granted a concession 
    allowing her not to fast, and she should make up the fasts after she 
    delivers and her nifaas has ended. End quote. 
See also question no. 
    50005. 
These texts from the 
    scholars indicate that it is not permissible for pregnant and breastfeeding 
    women to break the fast so long as fasting is not difficult for them. 
And Allaah knows best.