Baby's Development - Second Trimester

By now, your baby is sucking his finger, moving his arms and legs, and floating up and down. He may hear and respond to your voice, other voices and even music. He may be startled by other noises in your environment. We encourage you to talk to the baby (older brothers and sisters included), and play music for him. As your baby's movements become strong enough for you to feel, you'll begin to learn your baby's patterns.

Development Chart

Week 14 Hair and eyebrows are growing. Heartbeat registers on ultrasound. Baby drinks amniotic fluid.
Week 15 Middle-ear bones harden and baby can hear for the first time.
Week 16 Fine hair (called "lanugo"), appears all over the body and face. External genetial organs are visible with ultrasound.
Week 17 Fingernails and toenails begin to appear. Baby hears sounds outside the mother's body and may jump when startled. Baby may also begin thumb-sucking.
Week 18 Baby measures 8 inches long, and is moving much of the time now.
Week 19 Buds for permanent teeth begin to form. Baby may get hiccups.
Week 20 Baby's movements can now be felt by mother. Baby weighs between 8 and 16 ounces.
Week 21 Tongue is fully developed, and skin is becoming opaque.
Week 22 A greasy, white substance (known as "Vernix") is beginning to form on the baby's skin to protect it. (Most of this vanishes by birth.)
Week 23 Heartbeat is detectable by stethoscope.
Week 24 Lungs are immature, but other vital organs are developed enough for baby to survive outside the womb.
Week 25 Bone centers begin to harden.
Week 26 Fat stores are beginning to form.

Am I Having Twins?

Twins naturally occur once in every 41 births, and can be identical (formed from the same egg) or fraternal (formed from two separate eggs). Fraternal twins are more common than identical twins.

Your doctor or nurse-midwife can detect whether or not you are carrying "multiples" (twins, triplets or more) fairly early-on in your pregnancy. A quickly growing uterus, or more than one fetal heartbeat (detectable by ultrasound or stethoscope) are signs that you may be pregnant with more than one baby.

Mothers of multiples need to see their doctor or nurse-midwife more frequently, may require more prenatal tests, and may need additional time on bedrest. They also require more calories (2,700) each day, and their doctor or nurse-midwife may prescribe extra vitamins and minerals to help their babies grow. A woman pregnant with twins should gain a total of 35-45 pounds.

Important Note: About half of all multiples are born before 37 weeks, so be certain to look for signs of preterm labor.

Parenting in the NICU: Caring for Multiples

If you have more than one baby, you have the added challenge of getting to know each infant's needs and personality. Even in the NICU, your babies can show differences in their medical needs, preferences, how they respond to their surroundings and what they need from you. For instance, one baby might prefer a light touch, while the other prefers a firm hold. One baby might sleep calmly through sudden noises, while the other startles and cries. As you get to know your babies and their unique preferences, you can fit your responses to meet each child's needs.

Getting to know each child as an individual can be especially challenging at first, because you may feel there is not enough of you to go around. You may feel torn between babies, not knowing who needs you more.

  • Trust yourself to give each infant what he or she needs on any given day, or even hour by hour.
  • If there is a day when you feel especially drawn to one of your babies, spend more time there. Encourage your partner to focus on the other(s).
  • You can enlist the help of family members to spend time with your babies.
  • Let yourself appreciate and rely on the attention given by your babies' nurses. They are there to help you take care of your little ones.
  • Have confidence that your babies will do just fine, even if your attention is split some time. You can be flexible and so can they. By doing your best, you are given them enough to thrive.


When you have more than one baby, feeding decisions regarding the breast or bottle, breastmilk or formula, can seem complicated. You may be able to breastfeed them all, or one baby may feed better from a bottle. One baby may do better on breastmilk, and another on formula. Or you may try to pump milk for all your babies, and substitute formula when needed.

If breastfeeding them all is your ultimate goal, flexibility is key. Whatever the situation, take your time to figure out what works best for you and your babies. And expect to adjust your plans as your babies grow.


March of Dimes Share Your Story

An online community that serves NICU families. Share your story, participate in online discussions, meet other NICU families.

Mothering Multiples: Breastfeeding and Caring for Twins or More by Karen Kerkhoff Gromada (La Leche League International, 1999).

Mothers of Super Twins (MOST)
A support network of families who have or are expecting triplpets, quadruplets or more. Provides information, resources and emotional help. State chapters with area coordinators. (631) 859-1110.

National Organization of Mothers of Twins Club
Provides advice regarding multiples and makes referrals to local support groups. (800) 243-2276.

August 2009

Excerpted from the March of Dimes booklet, "Parent: You & Your Baby in the NICU", written in collaboration with Deborah L. Davis, Ph.D., and Mara Tesler Stein, Psy.D., authors of "Parenting Your Premature Baby and Child: The Emotional Journey."