thank you for watching, buenos noches! conjoined twin girls. little eva and erin sharing a body but with two healthy hearts. >> one, two -- >> one, two -- >> this parents' anguish as one grows stronger and the other weakens. >> you talk to them, you're going to get strong, you're going to survive this. >> could they survive separation surgery? >> knowing the girls and what they've gone through -- they're fighters. >> tonight the dramatic, risky procedure with two lives on the line. >> a prayer for brace. >> linsey davis on one family's emotional journey. >> was there ever a part of you that thought this might not work? >> and the moment that brought

>> this special edition of "nightline," "becoming two," will be right back.

your internet deserves the 100% fiber-optic network. with fios gigabit connection, you get the fastest internet available with download speeds up to 940 megs. it's your last chance to get fios gigabit connection with tv and phone for $79.99 a month online for the first year. plus, your choice of hbo or multi-room dvr service included for 2 years, all with a two year agreement. and verizon wireless customers can stream tv on the fios mobile app, data-free. hurry and switch now, this offer ends november 4th. go to getfios.com this is a special edition of "nightline." "becoming two." >> reporter: from the moment they were born, you couldn't see eva sandoval without seeing her sister erika.

conjoined twins. they have never known life apart. tonight we take you inside the complicated and risky surgery to separate them. >> have we anticipated all the potential risks? are we prepared to deal with a bad outcome? >> reporter: these two little lives on the line. was there ever a part of you that thought this might not work? the sandovals' journey begins in sacramento, california, in the spring of 2014. with three children almost out of the house, 44-year-old aida sandoval and her husband of 25 years, art, were looking forward to becoming empty nesters. but little do they know they're about to receive some life-changing news. >> i was having pain. then i told art about it. and he's like, go to the doctor, i think it's your ulcer. i said, i don't think it's my ulcer. >> reporter: to her surprise, aida finds out she's pregnant with not one but two babies. so what was your reaction? >> whoa.

>> shocked. >> shocked. shocked, like okay -- >> he was pretty quiet. >> we're not kids anymore. >> reporter: one month later, aida's doctor recommends she sees a specialist. she assumed because of her advanced age. >> it felt an eternity by the time the doctor came in. he said, we do find some abnormalities. they are twins. and he goes, they are conjoined. >> reporter: conjoined twins are a rare phenomenon. their chances of survival even rarer. about half are stillborn. only 35% survive beyond the first day. >> i think when you're hit with some news like that -- he didn't know how to deal with it. i didn't know how to deal with it. you don't know who to turn to. >> reporter: the sandovals went to dr. gary hartman at stanford lucille packard children's hospital. >> this is erika's pelvis -- >> reporter: an expert in the world of conjoined twins. but despite having six successful separation surgeries under his belt, he says every case presents itself own

>> we were pretty blunt. what we told them was we didn't know that they could be separated. we weren't real optimistic about quality of life. >> reporter: doctors gave them the option of terminating the pregnancy. did you ever have a moment where you thought, should we do this? >> i didn't. >> what was it that made you think, this is never an option to end this pregnancy? >> i feel it was my faith. >> we talked about it, like let's give them a chance. you know, if it's meant to be it's meant to be. >> reporter: after 33 weeks of pregnancy, the sandovals welcomed two baby girls into the world. erika rose and eva victoria. they are joined from the sternum all the way down to the pelvis, and they share a third leg. but they have two healthy hearts. >> you see them and they have tubes, they had the little covers over their eyes. they did ask us, you can't carry them, they're very fragile. you question yourself, are we doing the right

are strong. you're going to get through this. >> reporter: right from the start, they begin to defy the odds. but because they need specialized treatment, they must spend the first few months of their lives in the neonatal intensive care unit. >> when those beautiful girls were born, that family was very scared. mom would stand over by the window with the bed many feet away, and we were just working with her to come over and to touch the girls and to know where she could put her hands in a place that wouldn't hurt them. >> reporter: finally, at 7 months old, the girls are deemed strong enough to go home to sacramento. despite aida's 24 years as a mother, nothing could have prepared her for this. >> this is her feeding. so we're giving her 8 ounces what is she's getting, erika. >> reporter: even the simplest of tasks like bath time, and putting on clothes, bec

exercise in patience and creativity. >> so these were the little clothes that they wore. these were the little gowns that were made, trying to keep them dressed. something cute is what i wanted to put on them. >> velcro is a godsend, right? >> right. >> reporter: like other kids they hit all their first milestones but they do so together. this is from their first words. >> nana! >> nana? up! >> up! >> reporter: to learning how to stand. >> very nice, i appreciate that. >> reporter: not wanting to leave their specialized care, they must make the nearly three-hour journey to palo alto regularly for checkups. even during those uncomfortable car rides. the girls remain upbeat. they begin to develop their own personalities. eva, the talkative one.

but eva also becomes stronger and larger than her sister, off then drag, even throwing her around. over time, their health starts to decline. >> what's been the most trying time? >> all the utis. they're throwing up, they're dehydrated. >> eva. sister stay, don't bounce. >> the month of july, we were in the hospital practically the whole month. >> reporter: erika kept getting weaker and weaker. >> she was just basically getting smaller. eva was getting bigger. that was their point to say, we really have to do something about this. >> reporter: with concern mounting, the family and doctors decide they need to separate the 2-year-old girls now. were you able to explain to them at their age what was going to happen? >> i would always role play. when some magic's going to happen and dr.

magician. >> reporter: only 250 separation surgeries successfully performed in the world, doctors tell the sandovals there's a 30% chance one of the twins could die. was there ever a part of you that thought this might not work? >> a very small part. knowing the girls, how much -- what they've gone through, they're fighters. >> reporter: it's finally the morning of the surgery. the twins are their usual bubbly selves. >> ready to go now. >> reporter: two hours later, when they arrive at the hospital, reality sets in for the sandovals. they place their faith in god. and their babies in the hands of this team of specialists. the nearly 50-person medical team begins with a prayer for guidance. >> we will work together, a prayer for strength. >> reporter: in a nearby room, the sandovals and dozens of family members join in. >> our father who art in heaven,

hallowed be thy name. >> i felt a calmness come over me that it was going to be okay no matter what, what the outcome was. >> reporter: after four hours of careful prep, it's now time to begin the separation. >> they've made the first incision. >> reporter: the surgeons' plan is to separate the organs of the chest first, then move down to the abdomen and finish with the pelvis. they're hoping that the twins' shared leg can be given to erika. as the hours pass, the doctors encounter a few surprises. >> erika's small intestine joined eva's small intestine just before the large intestine. >> is that a problem? >> actually, you can be fine with just small intestine. >> reporter: having overcome that challenge, they continue the delicate dance of dividing the girls' organs. >> they were able to give -- split the bladder, so they each have a bladder. >> reporter: every step a daunting task. one false move could spell disaster. >> the big chaen

closing that wound. that's the real risky part. >> reporter: when we come back, aida and art are given difficult news. >> it's just like a punch in the gut. >> reporter: the long hours of waiting and that moment that brought everyone to tears. when you're close to the people you love, does psoriasis ever get in the way of a touching moment? if you have moderate to severe psoriasis, you can embrace the chance of completely clear skin with taltz. taltz is proven to give you a chance at completely clear skin. with taltz, up to 90% of patients had a significant improvement of their psoriasis plaques. in fact, 4 out of 10 even achieved completely clear skin. do not use if you are allergic to taltz. before starting you should be checked for tuberculosis. taltz may increase your risk of infections and lower your ability to fight them. tell your doctor if you are being treated for an infection or have symptoms. or if you have received a vaccine or plan to.

ppen with taltz. including worsening of symptoms. serious allergic reactions can occur. now's your chance at completely clear skin. just ask your doctor about taltz. depend silhouette briefs feature a comfortable, sleek fit. as a dancer, i've learned you can't have any doubts. because looking good on stage is one thing. but real confidence comes from feeling good out there. get a free sample at depend.com. but real confidence comes from feeling good out there. i was wondering if an electric toothbrusthan a manual.s better and my hygienist says it does but they're not all the same. who knew? i had no idea. so she said, look for one that's shaped like a dental tool with a round brush head. go pro with oral-b. oral-b's rounded brush head surrounds each tooth to gently remove more plaque. and unlike sonicare, oral-b is the only electric toothbrush brand accepted by the american dental association for its effectiveness and safety. my mouth feels so clean. i'll only use an oral-b. oral-b. brush like a pro.

when you ache and haven't you're not you. tylenol® pm relieves pain and helps you fall fast asleep and stay asleep. we give you a better night. you're a better you all day. tylenol®.

we are the tv doctors of america, and we may not know much about medicine, but we know a lot about drama. we also know that you can avoid drama by getting an annual check-up. so go, know, and take control of your health. it could save your life. cigna. together, all the way.

♪ ♪ 2-year-old conjoined twins erika and eva sandoval are undergoing an intense separation surgery. the past five hours, 13 surgeons at lucille packard children's hospital have had to carefully coordinate their

performing a difficult and delicate dance. and then finally -- >> they're two now. >> reporter: the prayers of their parents art and 8 deaida answered. the twins successfully separated. but the work of dr. hartman and his team is far from over. >> it seems like the most dramatic piece of the procedure and people are all focused on that. but that's just like step 34 of 50 or 60 steps. >> reporter: the surgical team now faces a new hurdle. they realize they don't have enough skin to close the girls' wounds. so they turn to that once-shared leg they were hoping to give to erika. it's now needed for something more crucial, its skin tissue. >> they had told us earlier that they may have been able to use that third leg and give to it

but when it came down to it, there wasn't enough tissue to cover erika. >> that was really hard. you know, it's just like a punch in the gut. >> reporter: but despite that setback, the rest of the surgery goes as planned. and after a total of 13 hours -- >> okay, we're good. >> reporter: the twins are wheeled into recovery. so tell me about the first time that you guys saw the girls after the surgery. >> i was excited just to know that they were alive still. just to know -- see them breathing. >> reporter: after spending their first six nights recovering in separate beds, the girls are reunited. in the weeks that follow, erika, the once-smaller twin, is now thriving. she makes tremendous progress at physical therapy.

>> one, two, three! >> she has figured out with this totally new body how to be really mobile really fast. >> reporter: but the road to recovery is not as easy for eva. >> eva. one -- two -- there you go. so with eva she's had a lot of pain, also anxiety. so a lot of our sessions are focused on trying to get her in more of an upright position. >> do you want to go see eva? >> yeah. >> reporter: ever her sister's keeper, erika tries to comfort eva. >> it's okay, it's okay. >> reporter: through it all, aida is mostly parenting solo.

>> i was working. i could be on the road all week. >> reporter: art, who's had to keep working full-time back at home to cover the medical expenses, drives the three hours every weekend to visit her and the girls. >> i'll do what i have to do to make things work. it's our life. and we adjust to it. and we keep on going. >> reporter: the hospital becomes like home for the girls, who haven't been outside in two months. >> can you see the clouds moving? what do you see in the clouds? >> elephant. >> you see an elephant in the clouds? here we go. >> outside. >> outside. mama? >> i'm right here. look at sister. >> reporter: finally after three months in the hospital, a breath of fresh air. an ambulance, while often a sign of tragedy and fear, on this day is one of hope. >> all r

look at you. >> reporter: erika and eva are making the journey home to sacramento. >> you ready to go? >> yeah. >> reporter: in the care of their local hospital, the girls continue physical therapy. >> hold on to your wheelchair. >> reporter: and are fitted for wheelcha wheelchairs. >> there you go, see? >> i just think it's amazing that we're at this point with them in their lives, you know. and feeling sick is not going to hold the other one back. >> reporter: now they're free to roam at home. >> i love it! >> reporter: where for the first time erika can go one way and eva can go the other. >> you guys play so nicely together. what is the best part in all of this? >> i love bringing them home and being a family. their smiles. >> reporter: mom and dad are settling into a new routine.

>> here we go. bye, friends! >> reporter: with every scoop or step they surpass all expectations. >> good job. you want to move your leg closer. >> reporter: no one was certain they would make it this far. >> this is actually the first that i've seen them both standing up like this. >> these girls are as healthy as they can be right now. they've gone way past what i thought they could do at this time. >> reporter: but they still have many challenges ahead. the girls have been on feeding tubes since birth and are just now getting used to eating solid foods. they're also not able to be fitted for prosthetic legs. but dr. hartman is hopeful that one day they can. >> yeah, we don't have a prosthesis right now that would work on a girl who has a complete pelvis, but nothing, no hip joint on that side. who knows what we're going to have in five years or ten years. >> you think walking is not out of the question? >> yeah, watching what they can do

>> reporter: the girls are embracing their independence as typical toddlers full of curiosity and mischief. >> somebody who was supposed to be taking a nap got down from her crib. >> reporter: but that connection they once shared, never far from memory. >> eva will see her, she goes, my sister was right here. yes, your sister was right there. we do talk about it. >> "she took my leg." >> she did say that, "she took my leg." where's your leg? "erika took it." >> reporter: after two years living as one, they're about to celebrate their 3rd birthday. their first as separate individuals. >> i'm going to be woody! >> reporter: at a party full of family and friends -- ♪ happy birthday to you >> reporter: the girls dress as

and even though they're on their own, in some ways they're still inseparable. >> i love watching them. they know that all these people are there and they're going to play with them. whether they have a disability or not, it's just being with people and doing kid stuff. >> are you ready? >> go, go, come on, eva, go, go, go! >> reporter: the girls fiercely fighting to be just like any other kids. >> would you do it all over again? >> i would. >> yeah. maybe a little younger. >> i know that god won't give you something you can't handle. there is nothing that these girls can't do. they are fully capable of doing anything. >> reporter: for "nightline," i'm linsey davis in sacramento, california. >> our thanks to linsey. we'll be right back.

they can fly... ...travel at the speed of light... ...and command the currents. they don't need another way to get around. or do they? [ engine revving ] with incredible flavors, like new nashville hot shrimp- crispy, spicy, and drizzled with sweet amber honey. plus the delicious classics you love, like garlic shrimp scampi. try all the shrimp you want,

but hurry, it ends soon. ♪i'm gonna get ya', get ya', get ya', get ya'♪ ♪one day maybe next week, ♪i'm gonna meet ya' ♪i'm gonna meet ya', i'll meet ya'♪ depend real fit briefs feature breathable, cotton-like fabric. in situations like this, there's no time for distractions. it's not enough to think i'm ready. i need to know i'm ready. no matter what lies ahead. get a free sample at depend.com. kelly! we're out of body wash! what are you doing?? i thought you had a cold?? i don't need all this. mucinex fast-max is powerful enough to handle pretty much every symptom. name one. how 'bout 9? sore throat, cough, even... yea--i can read, you know. we're done here. ahhh! boogers to betsy! mucinex fast-max. 9 symptoms. 1 dose. max strength. start the relief. ditch the misery. let's end this. and for kid's multi-symptom relief,

x.

optic network. with fios gigabit connection, you get the fastest internet available with download speeds up to 940 megs. it's your last chance to get fios gigabit connection with tv and phone for $79.99 a month online for the first year. plus, your choice of hbo or multi-room dvr service included for 2 years, all with a two year agreement. and verizon wireless customers can stream tv on the fios mobile app, data-free. hurry and switch now, this offer ends november 4th. go to getfios.com ♪ ♪

finally tonight, special thanks to the sandoval family. they taught us a lot about faith. hebrews 11:1 faith is the substance of the hopeful, evidence of things not seen. thanks for watching abc news. as always abcnews.com and our "nightline" facebook page. thanks for the company, america. good night. >> one of our contestants today may make more money in the next 30 minutes than they have in the past 30 years, so stay right there. it's time to play "who wants to be a millionaire." [cheers and applause] [dramatic music] ♪

you guys ready to play "millionaire" today? let's welcome our first contestant, who lived in finland and australia for the past 20 years. from santa clara, california, leslie shannon. [cheers and applause] welcome. >> thank you, thank you. >> welcome back to the united states, and welcome to "millionaire." >> thank you. >> you're about to face 14 questions. >> all right. >> the money value is growing from $500 all the way up to that $1 million. [cheers and applause] you have your three lifelines. they're there if and when you need 'em. >> okay. >> all right, let's play "who wants to be a millionaire." all right, leslie, we'll start you off with our $500 question. good luck. here we go. which of these does not appear on howstuffworks.com's list of "10 threats you should never try to outrun"? >> okay, we've got the old double negative happening in here, so the one that does not