While there is very little research, the simple answer is, "yes." In fact, in more traditional societies worldwide, it's quite common for conception to occur while breastfeeding. It's therefore important to realize that there are increased demands on your body during this time, and several things you should consider.
The first thing is your body’s nutrition. In order to ensure an adequate intake for your body, the growing baby in your womb, and your nursing child, it's important to take prenatal vitamins and eat a well-balanced, whole-foods diet.
It's also important to note that your milk supply may decrease. About mid-pregnancy, many women will notice their milk supply begin to decline; this is a hormonal change and usually doesn't increase with additional breastfeeds. Because of this drop in supply, the milk will begin to change in flavor, increasing in sodium content and decreasing in lactose. If your nursing child is old enough, she may even note the change in flavor of the milk. Despite this, your breast milk will still be completely nutritious and healthy for your child.
Another possible change you may notice is nipple tenderness. It's common during pregnancy for a woman’s nipples to become sore, and breastfeeding may make the tenderness even more intense. Since these are hormonal changes within the mother’s body, there's not much that can be done. In fact, this is the number one reason cited for weaning during pregnancy. You may consider decreasing the number of breastfeeds during the day to possibly give your nipples time to rest and help keep breastfeeding enjoyable for both mother and child.
Though these points should be considered, they do not need to constitute reasons for weaning your breastfeeding child if you both still want to continue. In fact, the World Health Organization, and many pediatric associations around the world, recommend breastfeeding your child until age two or beyond. Even once your new baby arrives, it's possible to continue to nurse both children. Tandem nursing is when a mother is breastfeeding two children of different ages at the same time.
In the past, some have noted that oxytocin, a hormone released while breastfeeding, is the same hormone released during labor that causes the uterus to contract. It had been supposed, therefore, that breastfeeding during pregnancy could cause preterm labor. But two studies have both concluded that there's no increased risk of preterm labor due to breastfeeding. The amount of oxytocin released while breastfeeding does not cause cervical effacement or dilation. If your pregnancy is high-risk and you are concerned about this issue, please discuss the risks and benefits with your health care provider.
Breastfeeding your child during pregnancy can be a wonderful and relaxing break to your very busy day. Since many women notice increased tiredness or fatigue during pregnancy, nursing your toddler throughout the day can provide a great opportunity to sit down and relax together before continuing with your hectic schedule. Breastfeeding can also be a way to comfort and prepare your child for the arrival of your new baby.
Prosser CG et al. (1984) Mammary gland function during gradual weaning and early gestation in women.
Moscone SR et al. (1993) Breastfeeding during pregnancy.
Flower H (2003) Adventures in Tandem Nursing.
Krista Gray is a La Leche League Leader and mother of four exclusively breastfed children, including twins. She is currently studying to take the IBCLC exam in 2013. Krista authors her website: http://www.nursingnurture.com