RhoGAM Shot

RhoGAM is given to prevent an Rh-negative mother’s immune system from producing antibodies against an Rh-positive baby’s blood, which could harm future pregnancies if the future baby is Rh-positive.
If both parents are Rh-negative, the baby cannot be Rh-positive.
Companies like Natera and Unity can test the fetal Rh(D) factor using NIPT. If your baby is Rh-negative you don’t need this shot.

Insert, Warning, Precauthions and Adverse Reactions

in RhoGAM manufacturor site you can see the full insert: 
RhoGAM is a human plasma–derived injection containing anti-D antibodies used to prevent Rh sensitization. A standard dose (300 µg / 1500 IU) prevents an immune response to up to 15 mL of Rh-positive red blood cells. It is made from carefully screened Rh-negative donors, and all plasma is extensively tested for viruses (including hepatitis, HIV, HAV, and parvovirus B19) to ensure safety before use.
The product contains no added human serum albumin (HSA), no thimerosal(mercury)
or other preservatives and utilizes a latex-free delivery system.
 
  • Serious allergic reactions are rare but possible, so RhoGAM is given in a medical setting where emergency treatment (like epinephrine) is available.
  • Because RhoGAM is made from human blood, there is a very small risk of transmitting infections, though extensive screening greatly reduces this risk.
  • RhoGAM can cause temporary positive blood test results because it adds antibodies to the blood.
  • If RhoGAM is given after an incompatible blood transfusion, patients are closely monitored for signs of red blood cell breakdown.
  • Common side effects are mild and include soreness, redness, swelling, or warmth at the injection site, mild fever, rash, or body aches.
  • Rare but serious side effects include severe allergic reactions and destruction of red blood cells.

Fetal-Maternal Hemorrhage (FMH) test:

  • It looks for fetal red blood cells in your bloodstream after delivery (or after any potential mixing event).
  • Normally, fetal and maternal blood do not mix.
  • If fetal cells are detected in your blood, it confirms that mixing has occurred.
There are two main methods:
a) Rosette screen (qualitative)
    • Detects presence or absence of fetal Rh-positive cells in maternal blood
    •  Tells you if any fetal blood has entered your circulation
b) Kleihauer–Betke (quantitative)
    • Counts how many fetal red cells are in maternal blood
    • Helps determine how much Rhogam you need (standard dose vs larger dose)
c) Flow cytometry (most precise)
    • Uses antibodies to detect fetal red cells specifically
    • Usually done in larger hospitals or reference labs
    • Provides accurate quantity if needed

Rate of Rh sensitization in Rh‑negative women who did not receive anti‑D prophylaxis

In this study, it is mentioned that “If Rh-negative mothers do not receive postpartum anti-D IgG prophylaxis after an Rh-positive baby, the incidence of sensitization during the next pregnancy is 12% to 16%, compared to 1.6% to 1.9% in mothers receiving postpartum prophylaxis receiving postpartum prophylaxis”.
there’s no large-scale study exactly linking every sensitized mother to exact clinical outcomes in babies.