She is breastfeeding two babies and is afraid that they will be harmed because of fasting
Question

 
I have twins who are five months old. They are not exclusively breastfed, because my milk is little; rather they are being bottle fed as well as breastfed. But I am afraid that my milk will be reduced because of fasting, and I will not be able to breastfeed them, so they will be weaned too early.
Is it permissible for me not to fast?
Praise be to Allah.Firstly: 
It is proven from the Messenger of Allah (blessings and peace of Allah be upon him) that he said: “Allah, may He be glorified and exalted, has relieved the traveller of half of the prayer, and He has relieved the traveller and pregnant and nursing mothers of the duty to fast.”
Narrated by Abu Dawood (2408), at-Tirmdhi (715), an-Nasaa’i (2275) and Ibn Majah (1667). Al-Albani said in Saheeh Abi Dawood: It is hasan saheeh. 
Although this hadeeth appears to be general in meaning and to apply to every pregnant woman and breastfeeding mother, it is restricted to cases where they fear harm to themselves or their babies. 
It says in Haashiyat as-Sindi ‘ala Sunan Ibn Maajah (1/512): “pregnant women and breastfeeding mothers” i.e., if they fear harm to the foetus or nursing infant, or to themselves. End quote. 
Al-Jassaas said in Ahkaam al-Quran (1/244), after mentioning the words of the Prophet, “Allah, may He be glorified and exalted, has relieved the traveller of half of the prayer, and He has relieved the traveller and pregnant and nursing mothers of the duty to fast”:
It is well-known that the concession granted to them – i.e., the pregnant woman and breastfeeding mother – depends on whether there is the fear of harm to themselves or to their infants. 
He also said (1/252):
It is very possible that the pregnant woman or breastfeeding mother, or their babies, may be harmed by fasting. Whichever is the case, not fasting is better for them and fasting is not allowed for them. But if fasting will not cause any harm to them or their infants, then they must fast, and it is not permissible for them not to fast. End quote. 
The scholars have mentioned this restriction in several texts. In fact it was narrated that the scholars were unanimously agreed upon it, as we have explained in detail in fatwa no. 66438. 
Based on that: 
If you fear that your babies will be harmed because of your fasting, due to the milk drying up or being reduced to an extent that will cause them harm, then in that case there is nothing wrong with you not fasting. 
Similarly, if you fear that you yourself may be exhausted by breastfeeding whilst fasting to an extent greater than can be borne in such cases, or that you will be harmed by it, then in that case there is no blame on you if you do not fast. 
But if it is thought most likely that fasting may cause a decrease in milk that will not adversely affect the babies, then in this case it is not permissible to not fast, especially since it is possible to make up for this slight decrease by bottlefeeding. 
It says in al-Umm by ash-Shaafa‘i (2/113): If a pregnant woman fears for her child, then she may break the fast. The same applies if a breastfeeding mother will clearly be adversely affected with regard to her milk. But if the reduction is something bearable, then she should not break the fast. Fasting may exacerbate some problems, but that is usually within bearable limits; it usually leads to a decrease in the milk supply, but that is usually within bearable limits too. But if it goes beyond bearable limits, then the pregnant woman and breastfeeding mother may break the fast.
End quote. 
Secondly: 
If the breastfeeding mother fears for her child and therefore breaks the fast, the fuqaha’ differed as to what is required of her. 
It says in al-Mawsoo‘ah al-Fiqhiyyah al-Kuwaitiyyah (32/69): 
… They differed concerning the case of a pregnant or breastfeeding woman who breaks her fast out of fear for her child. The Shaafa‘is, according to their most prevalent view, the Hanbalis and Mujaahid are of the opinion that they have to make up the fast and feed one poor person for each day, because they come under the same heading as those mentioned in the verse (interpretation of the meaning): “And as for those who can fast with difficulty, (e.g. an old man, etc.), they have (a choice either to fast or) to feed a Miskeen (poor person) (for every day)” [al-Baqarah 2:184]. The comment of Ibn ‘Abbaas (may Allah be pleased with him) on this verse has been quoted above. 
Ibn Qudaamah said: That was also narrated from Ibn ‘Umar (may Allah be pleased with him) and no one among the Sahaabah (may Allah be pleased with them) differed from that. Moreover, it is breaking the fast because of being unable to fast for a physical reason, so expiation must be offered for it, as in the case of the old man (who cannot fast). 
The Hanafis, ‘Ata’ ibn Abi Rabaah, al-Hasan, ad-Dahhaak, an-Nakha‘i, Sa‘eed ibn Jubayr, az-Zuhri, Rabee‘ah, al-Awzaa ‘i, ath-Thawri, Abu ‘Ubayd and Abu Thawr – and it is also one view among the Shaafa‘is – are of the view that they are not obliged to offer the fidyah (i.e., feeding the poor); rather that is mustahabb for them, because of the report narrated from the Prophet (blessings and peace of Allah be upon him), according to which he said: “Allah, may He be glorified and exalted, has relieved the traveller of half of the prayer, and He has relieved the traveller and pregnant and nursing mothers of the duty to fast.” 
The Maalikis and al-Layth – and it is a third view among the Shaafa‘is – were of the view that the pregnant woman may break the fast and should make it up, but she is not required to pay the fidyah; the breastfeeding mother may break the fast and she should make it up and pay the fidyah, because the breastfeeding woman can give her child to someone else to breastfeed him, unlike the pregnant woman, because the pregnancy is part of the pregnant woman, so fear for the pregnancy is like fear for one of her limbs or body parts. Moreover, the pregnant woman breaks the fast for a reason that is within herself, so she is like the person who is sick, whereas the breastfeeding mother breaks the fast for a reason that is separate from her, so she must pay the fidyah. 
Some of the earlier scholars – including Ibn ‘Umar, Ibn ‘Abbaas and Sa‘eed ibn Jubayr (may Allah be pleased with them) are of the view that they may break the fast and give food to the poor, but they do not have to make up the fast. End quote. 
What is more likely to be correct – and Allah knows best – is that they (the pregnant woman and the breastfeeding mother) only have to make up the fasts. 
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked, as it says in Fataawa as-Siyaam (p. 161): 
If a pregnant woman or breastfeeding mother breaks the fast with no excuse, and she is physically strong and has energy, and will not be affected by fasting, what is the ruling on that? He replied: 
It is not permissible for a pregnant woman or breastfeeding mother to break the fast during the day in Ramadan except with an excuse. If she breaks the fast with an excuse, then she must make up the fast, because Allah, may He be exalted, says concerning the sick person (interpretation of the meaning): “and whoever is ill or on a journey, the same number (of days which one did not observe Saum (fasts) must be made up) from other days” [al-Baqarah 2:185]. Pregnant and breastfeeding women come under the same heading as the sick person. 
If their excuse is fear for the infant, then – according to some of the scholars – in addition to making up the fasts they must also feed one poor person for each day, giving wheat, rice, dates or some other staple food. 
Some of the scholars said that they do not have to do anything other than making up the days in either case, because there is no evidence in the Quran or Sunnah for obliging them to feed the poor, and the basic principle is that a person is not obliged to do anything unless there is evidence to that effect. This is the view of Abu Haneefah (may Allah have mercy on him) and it is a strong view. 
He (may Allah have mercy on him) was also asked (Fataawa as-Siyaam, p. 162) about a pregnant woman who fears for herself or her child, and breaks the fast; what is the ruling? 
He replied: 
Our response is that the pregnant woman must be in one of two situations:
the first is that she is active and strong, and faces no difficulty, and her foetus is not affected. Such a woman is obliged to fast, because she has no excuse not to fast.
In the second case, the pregnant woman is not able to fast, either because the pregnancy is difficult for her, or she is physically weak, or some other reason. In this case she may not fast, especially if fasting will harm her foetus; in that case it is obligatory for her to refrain from fasting. If she does not fast then she is like others who do not fast because of some excuse; she must make up the fasts when that excuse is no longer applicable in her case. When she has given birth, she must make up the fast after she becomes pure following the end of nifaas (postpartum bleeding). But sometimes the excuse of pregnancy may cease, but it is immediately followed by another excuse, which is the excuse of breastfeeding. The breastfeeding mother may need to eat and drink, especially during the long days of summer when it is very hot. She may need to break the fast in order to be able to nourish her baby with her milk. In this case too we say to her: Break the fast, and when that excuse is no longer applicable to you, you should make up the fasts that you missed. 
Shaykh Ibn Baaz (may Allah have mercy on him) said in Majmoo‘ al-Fataawa (15/224): 
With regard to the pregnant woman and breastfeeding mother, it is proven from the Prophet (blessings and peace of Allah be upon him), in the hadeeth of Anas ibn Maalik al-Ka‘bi, as narrated by Ahmad and the authors of as-Sunan with a saheeh isnaad: He granted them a concession allowing them not to fast, and regarded them as being like the traveller. Thus it is known that they may break the fast and make it up later on, like the traveller. The scholars stated that they do not have the right to break the fast unless fasting is too difficult for them, as in the case of one who is sick, or they fear for their infants. And Allah knows best. 
See also the answers to questions no. 49794 and 50005 
And Allah knows best.